RFC3002: Overview of 2000 IAB Wireless Internetworking Workshop

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Network Working Group                                          D. Mitzel
Request for Comments: 3002                                         Nokia
Category: Informational                                    December 2000

         Overview of 2000 IAB Wireless Internetworking Workshop

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.


   This document provides an overview of a workshop held by the Internet
   Architecture Board (IAB) on wireless internetworking.  The workshop
   was hosted by Nokia in Mountain View, CA, USA on February 29 thru
   March 2, 2000.  The goal of the workshop was to assess current and
   future uses of Internet technology in wireless environments, to make
   recommendations on research and standardization tasks to improve
   acceptance of Internet network and transport protocols in wireless
   environments, and to evaluate methods to improve communication and
   collaboration among Internet standards working groups and those of
   the telephony and wireless sectors.  This report summarizes the
   conclusions and recommendations of the IAB on behalf of the IETF

   Comments should be submitted to the IAB-Wireless-Workshop@ietf.org
   mailing list.

Table of Contents

   1      Introduction  . . . . . . . . . . . . . . . . . . . .   3
   2      Presentation Overview . . . . . . . . . . . . . . . .   4
   3      Discussion and Observations . . . . . . . . . . . . .   9
   3.1    Discussion on "Walled Garden" Service Model . . . . .   9
   3.2    Discussion on Mobility and Roaming  . . . . . . . . .  10
   3.2.1  Discussion on Mobility and Roaming Model  . . . . . .  11
   3.2.2  Discussion on Mobility and Roaming Protocols  . . . .  11
   3.2.3  Discussion on Mobility and Roaming Services . . . . .  12
   3.3    Discussion on Security Model  . . . . . . . . . . . .  12
   3.3.1  Discussion on User Identity . . . . . . . . . . . . .  12
   3.3.2  Discussion on WAP Security  . . . . . . . . . . . . .  13

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   3.3.3  Discussion on 3G Network Security . . . . . . . . . .  13
   3.4    Discussion on Transports  . . . . . . . . . . . . . .  14
   3.4.1  Discussion on Link Characteristics and Mobility
          Effect on Transport . . . . . . . . . . . . . . . . .  14
   3.4.2  Discussion on WAP Transport . . . . . . . . . . . . .  16
   3.4.3  Discussion on IETF Transport Activities . . . . . . .  16
   3.5    Discussion on Aeronautical Telecommunication Network
          (ATN) Routing Policy. . . . . . . . . . . . . . . . .  17
   3.6    Discussion on QoS Services  . . . . . . . . . . . . .  18
   3.6.1  Discussion on "Last Leg" QoS  . . . . . . . . . . . .  18
   3.6.2  Discussion on Path QoS Discovery  . . . . . . . . . .  19
   3.7    Discussion on Header Compression  . . . . . . . . . .  20
   3.8    Discussion on Applications Protocols  . . . . . . . .  21
   3.9    Discussion on Proxy Agents  . . . . . . . . . . . . .  22
   3.10   Discussion on Adoption of IPv6  . . . . . . . . . . .  22
   3.11   Discussion on Signaling . . . . . . . . . . . . . . .  23
   3.12   Discussion on Interactions Between IETF and Other
          Standards Organizations . . . . . . . . . . . . . . .  24
   4      Recommendations . . . . . . . . . . . . . . . . . . .  25
   4.1    Recommendations on Fostering Interaction with Non-
          Internet Standards Organizations  . . . . . . . . . .  25
   4.2    Recommendations for Dealing with "Walled Garden"
          Model . . . . . . . . . . . . . . . . . . . . . . . .  26
   4.3    Recommendations on IPv4 and IPv6 Scaling  . . . . . .  27
   4.4    Recommendations on IPv4 and IPv6 Mobility . . . . . .  28
   4.5    Recommendations on TCP and Transport Protocols  . . .  29
   4.6    Recommendations on Routing  . . . . . . . . . . . . .  31
   4.7    Recommendations on Mobile Host QoS Support  . . . . .  32
   4.8    Recommendations on Application Mobility . . . . . . .  33
   4.9    Recommendations on TCP/IP Performance Characterization
          in WAP-like Environment . . . . . . . . . . . . . . .  33
   4.10   Recommendations on Protocol Encoding  . . . . . . . .  33
   4.11   Recommendations on Inter-Domain AAA Services  . . . .  34
   4.12   Recommendations on Bluetooth  . . . . . . . . . . . .  34
   4.13   Recommendations on Proxy Architecture . . . . . . . .  34
   4.14   Recommendations on Justifying IPv6-based Solutions for
          Mobile / Wireless Internet  . . . . . . . . . . . . .  35
   5      Security Considerations . . . . . . . . . . . . . . .  35
   6      Acknowledgments . . . . . . . . . . . . . . . . . . .  35
   7      Bibliography  . . . . . . . . . . . . . . . . . . . .  36
   A      Participants  . . . . . . . . . . . . . . . . . . . .  41
   B      Author's Address  . . . . . . . . . . . . . . . . . .  41
          Full Copyright Statement  . . . . . . . . . . . . . .  42

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1 Introduction

   Wireless technology, including wireless LANs, data transfer over
   cellular radio (GSM, 3GPP, etc), and mobile operations from aircraft
   and near earth spacecraft are becoming increasingly important.  Some
   market projections suggest that a mobile Internet in parallel with or
   augmenting the wired Internet may be comparable in size to the wired
   Internet as early as 2003.

   The wireless operators have not, however, chosen to use IPv4, TCP,
   full HTTP/HTML, and other applications for a variety of reasons.
   These relate to edge device cost, bandwidth limitations, perceived
   protocol imperfections, unnecessary complexities, the chattiness of
   the application protocols, and network layer addressing issues.
   Unfortunately, this creates some serious issues at the wired/wireless
   demarcation: end to end operation is sacrificed, security is
   compromised, and automated content modification in some form becomes
   necessary.  The IAB considers these to be serious fundamental issues,
   which will in time be a serious impediment to the usability of the
   combined Internet if not addressed.

   The Internet Architecture Board (IAB), on February 29 thru March 2,
   2000, held an invitational workshop on wireless internetworking.  The
   goal of the workshop was to assess current and future uses of
   Internet technology in wireless environments, to make recommendations
   on research and standardization tasks to improve acceptance of
   Internet network and transport protocols in wireless environments,
   and to evaluate methods to improve communication and collaboration
   among Internet standards working groups and those of the telephony
   and wireless sectors.

   The following topics were defined for discussion:

        + Local area wireless technologies

        + Cellular wireless technologies

        + Wireless Application Protocol (WAP)

        + Near-space and aviation wireless applications

        + Voice over IP (VoIP) over wireless networks

        + Security over wireless networks

        + Transport and QoS over wireless networks

        + Use of WWW protocols over wireless and small screen devices

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        + Addressing requirements for wireless devices

        + Compression and bit error requirements for wireless networks

   The fundamental question addressed in these discussion is "what are
   the issues, and what really needs to be done to unify the Internet
   below the application layer."  Applications will also need to be
   addressed, but were perceived to be more than could be usefully
   discussed in a three-day workshop, and probably require different

   Section 2 presents a concise overview of the individual presentations
   made during the workshop.  References to more extensive materials are
   provided.  Details on major discussion topics are provided in section
   3.  Section 4 presents the recommendations made to wireless
   operators, IRTF, and IETF on the architectural roadmap for the next
   few years.  It should be noted that not all participants agreed with
   all of the statements, and it was not clear whether anyone agreed
   with all of them.  However, the recommendations made are based on
   strong consensus among the participants.  Finally, section 5
   highlights references to security considerations discussed, appendix
   A lists contact information of workshop participants, and appendix B
   lists the author contact information.

2 Presentation Overview

      Title: Overview of Wireless IP Devices (Network Implications...)

      Presenter: Heikki Hammainen



      Title: Overview of IEEE 802.11 Wireless LAN's & Issues Running IP
           over IEEE 802.11?

      Presenter: Juha Ala-Laurila



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      Title: Overview of Bluetooth Wireless & Issues Running IP over

      Presenter: Pravin Bhagwat



      Title: Overview of Cellular Data Systems & Approaches to more IP
           centric Cellular Data System

      Presenter: Jonne Soinien



      Title: IP Packet Data Service over IS-95 CDMA

      Presenter: Phil Karn



      Title: Wireless Internet Networking

      Presenter: Chih-Lin I



      Title: Mobile IP in Cellular Data Systems

      Presenter: Charlie Perkins

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      Title: Overview of WAP

      Presenter: Alastair Angwin



      Title: Mobile Wireless Internet Forum (MWIF)

      Presenter: Alastair Angwin



      Title: Some WAP History

      Presenter: Jerry Lahti



      Title: Near-space Wireless Applications

      Presenter: Mark Allman



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      Title: Air Traffic / Aviation Wireless

      Presenter: Chris Wargo



      Title: VoIP over Wireless

      Presenter: Christian Huitema



      Title: Security Issues in Wireless Networks and Mobile Computing

      Presenter: N. Asokan



      Title: Security for Mobile IP in 3G Networks

      Presenter: Pat Calhoun



      Title: On Inter-layer Assumptions (A View from the Transport Area)

      Presenter: Mark Handley

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      Title: Does current Internet Transport work over Wireless?

      Presenter: Sally Floyd



      Title: QOS for Wireless (DiffServ, IntServ, other?)

      Presenter: Lixia Zhang



      Title: Do current WWW Protocols work over Wireless and Small
           Screen Devices?

      Presenter: Gabriel Montenegro



      Title: Compression & Bit Error Requirements for Wireless

      Presenter: Mikael Degermark

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      Title: Addressing Requirements for Wireless Devices & IPv6

      Presenter: Bob Hinden



3 Discussion and Observations

   During the workshop presentations a number of issues were discussed
   and observations made.  The following sections 3.1 -- 3.12 summarize
   these discussion and observations.  Rather than organizing the
   material linearly by presentation, it is grouped according to common
   "themes" and issues.

3.1 Discussion on "Walled Garden" Service Model

   Presentations from members involved in the cellular wireless (3GPP,
   3G.IP, MWIF) and WAP environments quickly illustrated a significant
   difference in protocol specification and service models from that
   typically assumed by the Internet community.  These communities focus
   on defining a profile (set of protocols and operational parameters)
   that combine to provide a well defined user service.  In addition,
   the carriers typically prefer to have complete (or as much as
   possible) control over the entire service, including user access
   device, transmission facilities, and service "content".  This style
   of service model appears to have been inherited from the classic
   telephony provider model.  The term "walled garden" was coined to
   describe the resulting captive customer economic and service model.
   That is, the user is constrained within the limits of the service
   provided by the carrier with limited ability to extend features or
   access services outside the provider.           The "walled garden"
   service model is in stark contrast to the "open" service assumed in
   the Internet.  The application, access device, and service content
   may each be controlled by a different entity, and the service
   provider is typically viewed as little more than a "bit pipe".

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   Additionally, specification typically define a standalone protocol or
   application rather than the set of features and interoperation with
   other components required to deploy a commercial service.

   Some discussion focused on whether cellular carriers could be
   persuaded to transition toward the Internet "open" service model.
   Responses indicated that there was little hope of this as carriers
   will always fight being reduced to a "bit pipe", fearing they cannot
   sustain sufficient revenues without the value added services.  An
   additional point raised was that the closed model of the "walled
   garden" simplifies a number of issues, such as security,
   authorization, and billing when the entire network is considered
   secured and controlled under a single administration.  These
   simplification can eliminate roadblocks to service deployment before
   scalable, interdomain solutions are available.

   Even though there seems little hope of evolving carriers away from
   the "walled garden" service in the short term, there was significant
   value in recognizing its presence.  This led to observations that
   "walled garden" Internet-based services will operate somewhat like
   current intranet services.  Also, mechanisms should be investigated
   to simplify interoperation and controlled access to the Internet.
   Finally, the difference between Internet protocol specification
   contrasted to service profiles highlights some of the confusion those
   in the telephony environment encounter when attempting to incorporate
   Internet capabilities.

   Much of the current work in extending Internet-based services to
   cellular customers has focused on data services such as email or web
   access.  One observation on the reluctance of carriers to release any
   control over services was that this may be an impediment to adoption
   of Internet-based voice services.  Current work on voice over IP
   (VoIP) and call signaling (SIP [30]) loosens control over these
   services, much of the functionality is moved into the SIP agent with
   the carrier being reduced to an access provider (i.e., "bit pipe").

3.2 Discussion on Mobility and Roaming

   An inherent characteristic of wireless systems is their potential for
   accommodating device roaming and mobility.  Some discussion focused
   on the model of mobility presented to the user.  There was also
   considerable interest and discussion on protocols employed, using
   cellular telephony and/or IP-based solutions.  Finally, there was
   some interest in exploring new services enabled by mobility.

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3.2.1 Discussion on Mobility and Roaming Model

   There was considerable discussion and concern over what style of
   mobility and roaming needs to be supported.  Current usage in the
   Internet is dominated by the mode where a user performs some actions
   at one location, then shuts down and moves, followed by restart at a
   new location.

   3G.IP uses the term "macro mobility" to describe this mode.

   The discussion attempted to discern whether the current mode of usage
   is a perceived limitation introduced by current protocols.  A clear
   consensus could not be achieved.  There was agreement that
   introduction of this "macro mobility" roaming is a worthwhile first
   step.  However, that was immediately followed by questions on whether
   it is a sufficient first step, and warning not to stop at this level.
   There seems significant issues for continued investigation related to
   enabling continual usage of a device during roaming ("micro
   mobility") and the ability to retrieve previous connections after a
   roaming event.

3.2.2 Discussion on Mobility and Roaming Protocols

   Selection between cellular and IP protocols in support of roaming
   provided another topic for significant discussion.  Cellular
   operators have already deployed protocols providing significant
   support for roaming.  This has led several efforts, such as 3GPP and
   3G.IP, toward architecture relying on telephone system for all
   mobility support, hiding roaming from the IP layer.

   Arguments for cellular-based roaming centered on concerns about the
   mobile IP model.  There was concern that home agent and foreign agent
   involvement in delivery might introduce bottleneck, and the
   perception that mobile IP handoff is too slow.  A rebuttal offered
   was that IETF mobileip working group is introducing hierarchy and
   route optimization to improve performance and robustness [50], and
   there was disagreement on the point regarding slow handoff under
   mobile IP.

   Detriments to the cellular-based roaming include the lack of IP
   support out to the mobile device and the added tunneling protocols
   and overhead required.  Additionally, roaming is less well defined
   when traversing service provider boundaries and may involve highly
   non-optimal forwarding path.  There appears significant work
   remaining to reach convergence on opinions, and additional
   investigation to support roaming across cellular, WLAN, and IP

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3.2.3 Discussion on Mobility and Roaming Services

   3G.IP mobility model is primarily focused on providing ubiquitous
   service across a range of access media.  However, the presentation
   also highlighted a desire to develop new "location based" services.
   Examples presented include locating nearby services or receiving
   advertisement and solicitations from nearby business.

   There are several Internet protocols defined, such as anycast service
   [47] and SLP [28], that may aid in developing location based
   services.  However, there was considerable frustration on the part of
   3G.IP in that there appears little commercial support of these
   protocols, and even less direction on how to assemble and coordinate
   the required protocols to deploy the desired services.

   This exchange illustrated the disconnect between interpreting
   Internet standards and telephony service profiles.  First, in the
   Internet many protocols are defined but many are optional.  Protocol
   support is typically driven by market demand, which can lead to
   "chicken and egg" problem.  Secondly, individual protocols and
   applications are developed rather than complete profile to compose a
   commercial service.  For this service, evaluating the usage and
   scalability of service discovery protocols appears to be an area open
   for further investigation.

3.3 Discussion on Security Model

   Mobility and wireless environments introduce many complexities and
   potential attacks to user authentication and privacy.  In addition to
   the discussion presented below, there was an overriding statement
   made regarding the methodology that must be followed for all security
   protocol development.  It was felt quite strongly that the only
   chance for success is that the definition be done in a public forum,
   allowing full disclosure of all algorithms and thorough review by
   security experts.  Stated an alternate way, defining protocols in a
   closed forum relying on cellphone manufacturers, or other non-experts
   on IP security, is very likely to create security exposures.

3.3.1 Discussion on User Identity

   Storage of user identity can have significant effect on device usage
   and device portability.  Discussion focused on whether identity
   should be tied to the mobile device or a transferable SIM card.
   Fixing identification with the device may simplify manufacture and
   provide some tamper resistance, however it makes it very difficult to
   deploy a public device taking on the identity of the user.  These
   alternative also affect transfer of identity and configuration state
   on device replacement or upgrade.

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   A related topic revolves around the user desire to employ a single
   device but to take on a different identity and privilege based on the
   usage at hand (e.g., to gain corporate access, home access, or
   Internet access).  The ability and ease of assuming these multiple
   identities may be highly dependent on the model of identity
   integration, as discussed above.  Discussion highlighted potential
   pitfalls based on tieing of device and user identities.  IPsec use of
   device IP address inhibits roaming capabilities as the address may
   change based on location, and precludes distinguishing identity and
   capabilities for current usage.  IPsec requires additional work to
   accommodate this added flexibility.

   A final topic of discussion on user identity establishment was
   whether possession of the device is sufficient, or whether the user
   should be required to authenticate to the device.  In the real world
   the first alternative is exemplified by the credit card model, while
   the second is more analogous to the ATM card where the user must also
   provide a PIN code.  Both models seem useful in the real world, and
   it's likely both will have uses in wireless networking.

3.3.2 Discussion on WAP Security

   WAP wireless transport security (WTLS) is based on TLS [20], with
   optimized handshake to allow frequent key exchange.  The security
   service employs a "vertical" integration model, with protocol
   components throughout the network stack.  Some argued that this is
   the wrong model.  A better approach may have been a security layer
   with well defined interfaces.  This could allow for later tradeoffs
   among different protocols, driven by market, applications, and device

   Additional statements argued that the WAP security model illustrates
   dangers from optimizing for a limited usage domain ("walled garden").
   Content provider systems requiring security (e.g., banks) must deploy
   a special WAP proxy, which breaks the model of a single WAP "domain".
   Similar issues are inherent in gatewaying to the Internet.

3.3.3 Discussion on 3G Network Security

   The existing GSM/GPRS model uses long term shared secrets (embedded
   in SIM card) with one-way authentication to the network, and with
   privacy only provided on the access link.  This is an example where
   the "walled garden" service model has an advantage.  Complete control
   over the service access devices and network greatly reduces the range
   of security concerns and potential attacks.

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   Future 3GPP and 3GPP2 plan to push IP all the way out to the wireless
   device.  An observation is that this results in more potential for
   exposure of signaling and control plane to attacks.  Desire is to
   perform mutual authentication and securing of the network.  This is a
   difficult problem with additional issues remaining to be solved;
   however the statement was made that relying on IP and open standards
   is more likely to produce a provably secure network than former
   reliance on SS7 protocols and obscurity.

   Completing support for the security requirements of the 3GPP/3GPP2
   network seems to require resolving issues in two primary areas, AAA
   services and mobile IP.  AAA is required for authentication,
   authorization, and billing.  Remaining issues center around cross
   domain AAA, authentication using PKI, and there was considerable
   aversion to use of IPsec and IKE protocols due to perceived overhead
   and delay.  Mobile IP issues revolve around solutions to reduce the
   security associations required between mobile node and home agent,
   mobile node and foreign agent, and the home and foreign agent.  An
   interim solution being investigated involves use of a RADIUS server
   [56]; however, there are concerns with repeated dynamic key
   generation on each handoff or hiding some details of handoffs, which
   may violate assumptions in mobile IP protocol [48].  Evaluating
   requirements and addressing all of these open issues appears to be an
   excellent opportunity for mutual cooperation on open standardization
   and review.

3.4 Discussion on Transports

   Discussion on transport protocols touched on a broad range of issues.
   Concerns ranged from the effects of wireless link characteristics and
   mobility effect on TCP, to development of new transport protocols
   such as WAP Wireless Transaction Protocol (WTP).  In addition, a
   significant amount of time was spent reviewing ongoing efforts within
   the IETF on TCP transport enhancements and investigation of new

3.4.1 Discussion on Link Characteristics and Mobility Effect on

   TCP makes assumptions on loss as congestion indication.  The
   statement was made that TCP was designed for links with about 1%
   corruption loss, and provided that constraint is met then TCP should
   function properly.  Presentation on IS-95 CDMA-based data service
   showed that it conditions line to provide 1--2% error rate with
   little correlation between loss.  Similar conditioning and Forward
   Error Correction (FEC) mechanisms may be appropriate for other
   wireless and satellite systems [4].  This may not be true for all
   wireless media, but it was interesting in the fact that it indicates

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   TCP should work properly on many wireless media.  However, the amount
   of discussion and suggestions on TCP performance optimizations showed
   that there can be a considerable gap between merely working and
   working well.

   One issue raised several times was related to the effects of non-
   congestive loss on TCP performance.  In the wireless environment
   non-congestive loss may be more prevalent due to corruption loss
   (especially if the wireless link cannot be conditioned to properly
   control error rate) or an effect of mobility (e.g., temporary outage
   while roaming through an area of poor coverage).  These losses can
   have great detrimental effect on TCP performance, reducing the
   transmission window and halving the congestion window size.  Much of
   the discussion focused on proposing mechanisms to explicitly indicate
   a non-congestive loss to the TCP source.  Suggestions included a
   Non-Congestive Loss Indication (NCLI) sent for instance when packet
   corruption loss is detected, or sending a Source Encourage (SE) to
   stimulate source transmission at the end of an outage.  In addition
   to data corruption, wireless links can also experience dropouts.  In
   this situation any active TCP sessions will commence periodic
   retransmissions, using an exponentially increasing back-off timer
   between each attempt.  When the link becomes available it may be many
   seconds before the TCP sessions resume transmission.  Mechanisms to
   alleviate this problem, including packet caching and triggered
   retransmission were discussed.  The more generic form of all of these
   mechanisms is one that allows the state of the layer two (datalink)
   system to signal to the TCP session its current operating mode.
   Developing a robust form of such a signaling mechanism, and
   integrating these signals into the end-to-end TCP control loop may
   present opportunities to improve TCP transport efficiency for
   wireless environments.

   TCP improvements have been incorporated to support "long" links
   (i.e., those with large delay and bandwidth characteristics) [36],
   however considerable expertise may still be required to tune socket
   buffers for maximum performance.  Some work has been done on auto-
   tuning buffers, which shows promise [58].  An additional problem with
   large windows and auto-tuning is the added header overheads.  This
   may exasperate the problems of running TCP over low bandwidth links.
   Suggestions included to explore dynamic negotiation of large window
   extensions in the middle of a connection to alleviate these issues.
   A final issue raised with regardport (see discussion below in section

   There was also concern regarding mobility effects on TCP performance.
   TCP has implicit assumptions on bounding propagation delay.  If delay
   exceeds the smoothed round trip time plus four times the round trip
   variance then the segment is considered lost, triggering the normal

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   backoff procedures.  Could these assumptions be violated by segment
   loss or duplication during handoff? Work on D-SACK [25] may alleviate
   these worries, detecting reordering and allowing for adaptive DUP-ACK
   threshold.  Finally, there was suggestion it might be appropriate to
   adapt (i.e., trigger slow start) immediately after mobile handoff on
   the assumption that path characteristics may differ.

3.4.2. Discussion on WAP Transport

   WAPF considered TCP connection setup and teardown too expensive in
   terms of bit overhead and latency when required for every
   transaction.  WAPF developed the Wireless Transaction Protocol (WTP),
   with some inspiration from T/TCP [12].  WTP offers several classes of
   service ranging from unconfirmed request to single request with
   single reply transaction.  Data is carried in the first packet and
   3-way handshake eliminated to reduce latencies.  In addition
   acknowledgments, retransmission, and flow control are provided.

   Discussion on WTP centered on assessing details on its operation.
   Although it incorporates mechanisms for reliability and flow control
   there was concern that it may miss critical or subtle transport
   issues learned through years of Internet research and deployment
   experience.  One potential area for disaster appeared to be the use
   of fixed retransmission timers and lack of congestion control.  This
   gave rise to suggestions that the IETF write up more details on the
   history and tradeoffs in transport design to aid others doing
   transport design work, and secondly that the IETF advocate that the
   congestion control is not optional when using rate adaptive transport

   The remaining discussion on WAP transport primarily focused on ways
   to share information.  It was suggested that any result from WAPF
   study of TCP shortcomings that led to its rejection might be useful
   for IETF review as inputs for TCP modifications.  Similar comments
   were raised on study of T/TCP shortcomings and its potential exposure
   to Denial of Service (DoS) attacks.  It was also encouraged that the
   WAPF members participate in the IETF directly contribute requirements
   and remain abreast of current efforts on evolving TCP operation and
   introduction of new transport (see discussion below in section

3.4.3 Discussion on IETF Transport Activities

   Discussion on transport work in the IETF presented a large array of
   activities.  Recent work on transport improvement includes path MTU,
   Forward Error Correction (FEC), large windows, SACK, NewReno Fast
   Recovery, ACK congestion control, segment byte counting, Explicit
   Congestion Notification (ECN), larger initial transmit windows, and

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   sharing of related TCP connection state [3,4,5,6,24,25,43,53,63].
   Work on new transports includes SCTP [61] in the IETF Signaling
   Transport (sigtran) working group and TCP-Friendly Rate Control
   (TFRC) [1] by researchers at ACIRI.  SCTP provides a reliable UDP-
   like protocol supporting persistent associations and in-order
   delivery with congestion control.  TFRC is targeted at unreliable,
   unicast streaming media.  Finally, work in the IETF End-point
   Congestion Management (ecm) working group is looking at standardizing
   congestion control algorithms, and work in the Performance
   Implications of Link Characteristics (pilc) working group is
   characterizing performance impacts of various link technologies and
   investigating performance improvements.

   This vast array of ongoing research and standards development seemed
   a bit overwhelming, and there was considerable disagreement on the
   performance and applicability of several TCP extensions.  However,
   this discussion did raise a couple of key points.  First, transport
   work within the Internet community is not stagnant, there is a
   significant amount of interest and activity in improvement to
   existing protocols and exploration of new protocols.  Secondly, the
   work with researchers in satellite networking has demonstrated the
   tremendous success possible in close collaboration.  The satellite
   networking community was dissatisfied with initial TCP performance on
   long delay links.  Through submission of requirements and
   collaborative investigation a broad range of improvements have been
   proposed and standardized to address unique characteristics of this
   environment.  This should hopefully set a very positive precedent to
   encourage those in the wireless sector to pursue similar
   collaboration in adoption of Internet protocols to their environment.

3.5 Discussion on Aeronautical Telecommunication Network (ATN) Routing

   The Aeronautical Telecommunication Network (ATN) has goals to improve
   and standardize communications in the aviation industry.  This ranges
   across air traffic management and control, navigation and
   surveillance, all the way up to passenger telephone service and
   entertainment.  This also involves integration of both fixed ground
   segments and mobile aircraft.  Supporting the ATN architecture using
   Internet protocols may introduce additional requirements on the
   routing infrastructure.

   Current ATN views each aircraft as an autonomous network (AS) with
   changing point of attachment as it "roams" through different
   airspace.  Addressing information associated with the aircraft is
   fixed, which makes route aggregation difficult since they're not
   related to topology, and also increases the frequency of updates.
   Additionally, the aircraft may be multiply attached (within coverage

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   of multiple ground and space-based access networks), requiring
   routing policy support for path selection.  Finally, QoS path
   selection capabilities may be beneficial to arbitrate shared access
   or partition real-time control traffic from other data traffic.

   Initial prototype of ATN capabilities have been based on ISO IDRP
   [33] path selection and QoS routing policy.  There was some
   discussion whether IDRP could be adopted for use in an IP
   environment.  There was quick agreement that the preferred solution
   within the IETF would be to advance BGP4++ [8,54] as an IDRP-like
   replacement.  This transitioned discussion to evaluation of ATN use
   of IDRP features and their equivalent to support in BGP.  Several
   issues with BGP were raised for further investigation.  For example,
   whether BGP AS space is sufficient to accommodate each aircraft as an
   AS? Also issues with mobility support; can BGP provide for
   dynamically changing peering as point of attachment changes, and
   alternative path selection policies based on current peerings? A
   significant amount of additional investigation is required to fully
   assess ATN usage of IDRP features, especially in the QoS area.  These
   could lead to additional BGP requirements, for instance to effect
   different prioritization or path selection for aircraft control vs.
   passenger entertainment traffic.

3.6 Discussion on QoS Services

   Enabling support for voice and other realtime services along with
   data capabilities requires Quality of Service (QoS) features to
   arbitrate access to the limited transmission resources in wireless
   environment.  The wireless and mobile environment requires QoS
   support for the last leg between the mobile device and network access
   point, accommodating roaming and unique characteristics of the
   wireless link.

   In addition to the discussion presented below, it was felt quite
   strongly that it is critical any QoS facility be provided as an
   underlying service independent of payload type.  That is, there
   should be no built in knowledge of voice or other application
   semantics.  This results in a feature that can be leveraged and
   easily extended to support new applications.

3.6.1 Discussion on "Last Leg" QoS

   Discussion on voice over IP (VoIP) emphasized that (wireless) access
   link is typically the most constrained resource, and while contention
   access (CSMA) provides good utilization for data it is not ideal for
   voice.  Two models were identified as potential solution in VoIP
   architecture.  The first is to have the wireless device directly
   signal the local access router.  A second alternative is to have the

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   call control element (SIP agent [30]) "program" the edge router.
   This tradeoff seemed to be an area open for additional investigation,
   especially given the complications that may be introduced in the face
   of mobility and roaming handoffs.  This appears a key component to
   solve for success in VoIP adoption.

   Work within the IEEE 802.11 WLAN group identified similar
   requirements for QoS support.  That group is investigating a model
   employing two transmission queues, one for realtime and one for
   best-effort traffic.  Additional plans include mapping between IP
   DiffServ markings [14,46] and IEEE 802 priorities.

   The statement was also made that QoS over the wireless link is not
   the fundamental problem, rather it is handling mobility aspects and
   seamless adaptation across handoffs without service disruption.
   There were concerns about mechanisms establishing per-flow state
   (RSVP [13]).  Issues include scaling of state, and signaling overhead
   and setup delays on roaming events.  DiffServ [9] approach allows
   allocating QoS for aggregate traffic class, which simplifies roaming.
   However, DiffServ requires measurement and allocation adjustment over
   time, and policing to limit amount of QoS traffic injected.

3.6.2 Discussion on Path QoS Discovery

   The HDR high speed wireless packet data system under development at
   Qualcomm highlights unique characteristics of some wireless media.
   This system provides users a channel rate between 38.4Kb/s and
   2.4Mb/s, with throughput dependent on channel loading and distance
   from network access point.  This gave rise to considerable discussion
   on whether it might be possible to discover and provide feedback to
   the application regarding current link or path QoS being received.
   This might enable some form of application adaptation.

   In the case of the HDR system it was indicated that no such feedback
   is currently available.  Additionally, it was argued that this is in
   accord with the current Internet stack model, which does not provide
   any mechanisms to expose this type of information.  Counter arguments
   stated that there are growing demands in Internet QoS working groups
   requesting exposure of this type of information via standardized
   APIs.  Members working on GPRS protocols also indicated frustration
   in deploying QoS capabilities without exposure of this information.
   This clearly seemed a topic for further investigations.

   A final area of discussion on QoS discovery focused on the question
   of how a server application might find out the capabilities of a
   receiver.  This could allow for application adaptation to client
   device and path characteristics.  One suggestion proposed use of RSVP
   payload, which is able to transport QoS information.  A second

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   alternative is to push capability exchange and negotiation to the
   application layer.  Discussion on this topic was brief, as
   application issues were deemed outside the workshop charter, however
   this also seems an area open for future investigation.

3.7 Discussion on Header Compression

   A critical deterrent to Internet protocol adoption in the highly
   band-width constrained wireless cellular environment is the bit
   overhead of the protocol encoding.  Examples presented highlighted
   how a voice application (layered over IP [52,19], UDP [51], and RTP
   [57]) requires a minimum of 40 bytes of headers for IPv4 or 60 bytes
   for IPv6 before any application payload (e.g., 24 byte voice sample).
   This overhead was also presented as a contributing factor for the
   creation of WAP Wireless Datagram Protocol (WDP) rather than IP for
   very low datarate bearers.

   Discussion on header compression techniques to alleviate these
   concerns focused on work being performed within the IETF Robust
   Header Compression (rohc) working group.  This working group has
   established goals for wireless environment, to conserve radio
   spectrum, to accommodate mobility, and to be robust to packet loss
   both before the point where compression is applied and between
   compressor and decompressor.  Additional requirements established
   were that the technique be transparent, does not introduce additional
   errors, and that it is compatible with common protocol layerings
   (e.g., IPv4, IPv6, RTP/UDP/IP, TCP/IP).

   The primary observation was that this problem is now largely solved!
   The working group is currently evaluating the ROCCO [38] and ACE [42]
   protocols, and expects to finalize its recommendations in the near
   future.  It was reported that these encodings have a minimum header
   of 1 byte and result in average overhead of less than 2 bytes for an
   RTP/UDP/IP packet.  There is some extra overhead required if
   transport checksum is required and some issues still to be analyzed
   related to interoperation with encryption and tunneling.

   A detriment to IPv6 adoption often cited is its additional header
   overhead, primarily attributed to its larger address size.  A
   secondary observation made was that it's believed that IPv6
   accommodates greater header compression than IPv4.  This was
   attributed to the elimination of the checksum and identification
   fields from the header.

   Discussion on use of WWW protocols over wireless highlighted protocol
   encodings as another potential detriment to their adoption.  A number
   of alternatives were mentioned for investigation, including use of a
   "deflate" Content-Encoding, using compression with TLS [20], or

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   Bellovin's TCP filters.  Observation was made that it could be
   beneficial to investigate more compact alternative encoding of the
   WWW protocols.

3.8 Discussion on Applications Protocols

   IETF protocol developments have traditionally taken the approach of
   preferring simple encode/decode and word alignment at the cost of
   some extra bit transmissions.  It was stated that optimizing protocol
   encoding for bit savings often leads to shortcomings or limitations
   on protocol evolution.  However, it was also argued that environments
   where physical limitations have an effect on transmission capacity
   and system performance may present exceptions where optimized
   encodings are beneficial.  Cellular wireless and near-space satellite
   may fall into this category.

   The WAP protocols exhibit several examples where existing Internet
   protocols were felt to be too inefficient for adoption with very low
   datarate bearer services and limited capability devices.  The WAP
   Wireless Session Protocol (WSP) is based on HTTPv1.1 [23], however
   WSP incorporates several changes to address perceived inefficiencies.
   WSP uses a more compact binary header encoding and optimizations for
   efficient connection and capability negotiation.  Similarly, the WAP
   Wireless Application Environment (WAE) uses tokenized WML and a tag-
   based browser environment for more efficient operation.

   Additional requests for more efficient and compact protocol
   encodings, and especially improved capability negotiation were raised
   during discussion on usage of WWW protocols with wireless handheld

   Finally, work within the near-space satellite environment has pointed
   out other physical limitations that can affect performance.  In this
   case the long propagation delays can make "chatty" protocols highly
   inefficient and unbearable for interactive use.  This environment
   could benefit from protocols that support some form of "pipelining"

   There seemed broad agreement that many of these observations
   represent valid reasons to pursue optimization of protocol
   operations.  Investigation of compact protocol encoding, capability
   negotiation, and minimizing or overlapping round trips to complete a
   transaction could all lead to improved application performance across
   a wide range of environments.

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3.9 Discussion on Proxy Agents

   Proxy agents are present in a number of the wireless and mobile
   architectures.  They're often required to gateway between
   communication domains; terminate tunnel and translate between
   telephony system and Internet protocols (GPRS), or to escape the
   "walled garden" (WAP).  In conjunction with limited capability
   handheld devices a proxy might be deployed to offload expensive
   processing such as public key operations, perform content filtering,
   or provide access to "backend" applications (e.g., email, calendar,
   database).  In other cases the proxy may be required to work around
   protocol deployment limitations (e.g., NAT with limited IPv4

   The discussion on proxy agents primarily recognized that there are a
   range of proxy agent types.  Proxies may operate by intercepting and
   interpreting protocol packets, or by hijacking or redirecting
   connections.  Some types of proxy break the Internet end-to-end
   communication and security models.  Other proxy architectures may
   limit system scalability due to state or performance constraints.
   There was some desire to conduct further study of proxy agent models
   to evaluate their effect on system operation.

3.10 Discussion on Adoption of IPv6

   Projections were presented claiming 1200 million cellular (voice)
   subscribers, 600 million wired stations on the Internet, and over 600
   million wireless data ("web handset") users by the year 2004.  Right
   up front there was caution about these projections, especially the
   wireless data since it is highly speculative with little history.
   Secondly, there was some doubt regarding potential for significant
   revenues from user base over 1 billion subscribers; this may be
   pushing the limits of world population with sufficient disposable
   income to afford these devices.  However, there was broad consensus
   that cellular and Internet services are going to continue rapid
   growth and that wireless data terminals have potential to form a
   significant component of the total Internet.  These conclusions
   seemed to form the basis for many additional recommendations to push
   for adoption of IPv6 protocols in emerging (3G) markets.

   In nearly all the presentations on 3G cellular network technologies
   discussion on scaling to support the projected large number of
   wireless data users resulted in strong advocacy by the Internet
   representatives for adoption of IPv6 protocols.  There were some
   positive signs that groups have begun investigation into IPv6.  For
   example, 3GPP has already defined IPv6 as an option in their 1998 and
   1999 specifications (release R98 and R99), and are considering

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   specifying IPv6 as mandatory in the release 2000.  The MWIF effort is
   also cognizant of IPv4 and IPv6 issues and is currently wrestling
   with their recommendations in this area.

   Although there was limited positive signs on IPv6 awareness,
   indication is that there are long fights ahead to gain consensus for
   IPv6 adoption in any of the 3G standards efforts.  There was
   considerable feedback that the telephony carriers perceive IPv6 as
   more difficult to deploy, results in higher infrastructure equipment
   expenses, and adds difficulty in interoperation and gatewaying to the
   current (IPv4) Internet.  Arguments for sticking with IPv4 primarily
   came down to the abundance and lower pricing of IPv4-based products,
   and secondary argument of risk aversion; there is currently minimal
   IPv6 deployment or operational experience and expertise, and the
   carriers do not want to drive development of this expertise.
   Finally, some groups argue IPv4 is sufficient for "walled garden"
   use, using IPv4 private address space (i.e., the "net 10" solution).

   One other area of concern regarding IPv6 usage is perceived memory
   and processing overhead and its effect on small, limited capability
   devices.  This was primarily directed at IPv6 requirement for IPsec
   implementation to claim conformance.  Arguments that continued
   increase in device capacity will obviate these concerns were
   rejected.  It was stated that power constraints on these low-end
   devices will continue to force concerns on memory and processing
   overhead, and impact introduction of other features.  There was no
   conclusion on whether IPsec could be made optional for these devices,
   or the effect if these devices were "non-compliant".

   Emerging 3G cellular networks appear ideal environment for IPv6
   introduction.  IPv6 addresses scaling requirements of wireless data
   user projections and eliminates continued cobbling of systems
   employing (IPv4) private address space and NAT.  This appears an area
   for IAB and Internet community to take a strong stance advocating
   adoption of IPv6 as the various 3G forums wrestle with their

3.11 Discussion on Signaling

   Discussion on signaling focused on call setup and control functions,
   and the effects of mobility.  The 3G.IP group has investigated
   standardizing on either H.323 [32] or SIP [30].  Currently support
   seems to be split between the protocols, and neither seemed ideal
   without support for mobility.  During discussion on VoIP it was
   presented that SIP does support mobility, with graceful handling of
   mobile handoff, updating location information with remote peer, and
   even simultaneous handoff of both endpoints.  The problem with SIP
   adoption seems to be its slow standardization brought about by

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   focusing on the harder multicast model rather than expediting
   definition of a unicast "profile".  There seems great need for IETF
   to expedite finalization of SIP, however some argued at this point
   it's likely many products will need to develop support for both SIP
   and H.323, and for their interoperation.

   A short discussion was also raised on whether it is the correct model
   to incorporate the additional protocol mechanisms to accommodate
   mobility into the SIP signaling.  An alternative model might be to
   build on top of the existing mobile IP handoff facilities.  There was
   no conclusion reached, however it seemed an area for further

3.12 Discussion on Interactions Between IETF and Other Standards

   There were many examples where non-IETF standards organizations would
   like to directly adopt IETF standards to enable Internet (or similar)
   services.  For example IEEE 802.11 WLAN relies on adoption of IETF
   standards for mobile IP, end-to-end security, and AAA services.  3GPP
   is looking into the IETF work on header compression.  WAPF derived
   its transport, security, and application environment from Internet
   protocols.  At first glance these would seem successes for adoption
   of Internet technologies, however the decision to rely on IETF
   standards often introduced frustrations too.

   One common theme for frustration is differences in standardization
   procedures.  For instance, 3GPP follows a strict model of publishing
   recommendations yearly; any feature that cannot be finalized must be
   dropped.  On the other hand the IETF working groups have much less
   formalized schedules, and in fact often seem to ignore published
   milestone dates.  This has led to a common perception within other
   standards organizations that the IETF cannot deliver [on time].

   A second area identified where IETF differs from other organizations
   is in publication of "system profile".  For example defining
   interoperation of IPsec, QoS for VoIP and video conferencing, and
   billing as a "service".  Wading through all the protocol
   specifications, deciding on optional features and piecing together
   the components to deliver a commercial quality service takes
   considerable expertise.

   Thirdly, there was often confusion about how to get involved in IETF
   standards effort, submit requirements, and get delivery commitments.
   Many people seem unaware and surprised at how open and simple it is
   to join in IETF standardization via working group meetings and
   mailing list.

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   There wasn't really a large amount of discussions on ways to address
   these differences in standards practices.  However, it did seem
   beneficial to understand these concerns and frustrations.  It seemed
   clear there can be some benefits in improving communication with
   other standards organizations and encouraging their participation in
   IETF activities.

4 Recommendations

   The IAB wireless workshop provided a forum for those in the Internet
   research community and in the wireless and telephony community to
   meet, exchange information, and discuss current activities on using
   Internet technology in wireless environments.  However the primary
   goal from the perspective of the IAB was to reach some understanding
   on any problems, both technical or perceived deficiencies, deterring
   the adoption of Internet protocols in this arena.  This section
   documents recommendations of the workshop on actions by the IAB and
   IESG, IRTF research efforts, and protocol development actions for the
   IETF to address these current deficiencies and foster wider
   acceptance of Internet technologies.

4.1 Recommendations on Fostering Interaction with Non-Internet Standards

   A clear consensus of the workshop is that dialog needs to be
   improved.  The Internet community should attempt to foster
   communication with other standards bodies, including WAPF, MWIF,
   3GPP, 3G.IP, etc.  The goal is to "understand each others problems",
   provide for requirements input, and greater visibility into the
   standardization process.


   It was recommended to take a pragmatic approach rather than
   formalizing liaison agreements.  The formalized liaison model is
   counter to the established Internet standards process, is difficult
   to manage, and has met with very limited success in previous trials.
   Instead, any relevant IETF working group should be strongly
   encouraged to consider and recommend potential liaison requirements
   within their charter.


   It was recommended to avoid formation of jointly sponsored working
   groups and standards.  Once again this has shown limited success in
   the past.  The preferred mode of operation is to maintain separate
   standards organizations but to encourage attendance and participation
   of external experts within IETF proceedings and to avoid overlap.

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   An exception to this style of partitioning meeting sponsorship is
   less formal activities, such as BOFs.  It was recommended that
   sponsoring joint BOF could be beneficial.  These could enable
   assembly of experts from multiple domains early in the process of
   exploring new topics for future standards activities.


   A principle goal of fostering communication with other standards
   organizations is mutual education.  To help in achieving this goal
   recommendations were made related to documenting more of the history
   behind Internet standards and also in coordinating document reviews.

   It was recommended that IETF standards groups be encouraged to create
   or more formally document the reasons behind algorithm selection and
   design choices.  Currently much of the protocol design history is
   difficult to extract, in the form of working group mail archives or
   presentations.  Creation of these documents could form the basis to
   educate newcomers into the "history" and wisdom behind the protocols.

   It was recommended that mutual document reviews should be encouraged.
   This helps to disseminate information on current standards activities
   and provides an opportunity for external expert feedback.  A critical
   hurdle that could severely limit the effectiveness of this type of
   activity is the intellectual property and distribution restrictions
   some groups place on their standards and working documents.

4.2 Recommendations for Dealing with "Walled Garden" Model

   There are several perceived benefits to the "walled garden" (captive
   customer) model, similar to current deployment of "intranets".  These
   range from simplified user security to "captive customer" economic
   models.  There was disagreement on the extent this deployment model
   might be perpetuated in the future.  However it is important to
   recognize this model exists and to make a conscious decision on how
   to accommodate it and how it will affect protocol design.


   It was strongly recommended that independent of the ubiquity of the
   "walled garden" deployment scenario that protocols and architectural
   decisions should not target this model.  To continue the success of
   Internet protocols at operating across a highly diverse and
   heterogeneous environment the IETF must continue to foster the
   adoption of an "open model".  IETF protocol design must address
   seamless, secure, and scalable access.

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   Recognition that the "walled garden" model has some perceived
   benefits led to recommendations to better integrate it into the
   Internet architecture.  These focused on service location and escape
   from the "walled garden".

   It was recommended to investigate standard protocols for service and
   proxy discovery within the "walled garden" domain.  There are already
   a number of candidate mechanisms, including static preconfiguration,
   DNS [22,27,44,45], BOOTP [18], DHCP [21], SLP [28], and others.
   Specific recommendations on use of these protocols in this
   environment can help foster common discovery methods across a range
   of access devices and ease configuration complexity.

   It was recommended to investigate standard methods to transport
   through the garden wall (e.g., escape to the Internet).  It seemed
   clear that a better model is required than trying to map all access
   over a HTTP [23] transport connection gateway.  One suggestion was to
   propose use of IP!

4.3 Recommendations on IPv4 and IPv6 Scaling

   Wireless operators are projecting supporting on the order of 10's to
   100's million users on their Internet-based services.  Supporting
   this magnitude of users could have severe scaling implications on use
   of the dwindling IPv4 address space.


   There was clear consensus that any IPv4-based model relying on
   traditional stateless NAT technology [60] is to be strongly
   discouraged.  NAT has several inherent faults, including breaking the
   Internet peer-to-peer communication model, breaking end-to-end
   security, and stifling deployment of new services [16,29,31].  In
   addition, the state and performance implications of supporting 10's
   to 100's million users is cost and technologically prohibitive.


   Realm specific IP (RSIP) [10,11] has potential to restore the end-
   to-end communication model in the IPv4 Internet, broken by
   traditional NAT.  However there was considerable reluctance to
   formally recommend this as the long term solution.  Detriments to its
   adoption include that the protocol is still being researched and
   defined, and potential interactions with applications, QoS features,
   and security remain.  In addition, added signaling, state, and
   tunneling has cost and may be technologically prohibitive scaling.

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   The clear consensus of the workshop was to recommend adoption of an
   IPv6-based solution to support these services requiring large
   scaling.  Adoption of IPv6 will aid in restoring the Internet end-
   to-end communication model and eliminates some roaming issues.
   Adoption of IPv6 in this marketspace could also help spur development
   of IPv6 products and applications, and hasten transition of the
   Internet.  It was recognized that some application gateways are
   required during transition of the IPv4 Internet, however it was felt
   that the scaling and roaming benefits outweighed these issues.


   It was recommended that an effort be made to eliminate any
   requirement for NAT in an IPv6 Internet.  The IAB believes that the
   IPv6 address space is large enough to preclude any requirement for
   private address allocation [55] or address translation due to address
   space shortage [15].  Therefore, accomplishing this should primarily
   require installing and enforcing proper address allocation policy on
   registry and service providers.  It was recommended to establish
   policies requiring service providers to allocate a sufficient
   quantity of global addresses for a sites use.  The feeling was that
   NAT should be easily eliminated provided efficient strategies are
   defined to address renumbering [17,62] and mobility [37] issues.

4.4 Recommendations on IPv4 and IPv6 Mobility

   An inherent characteristic of wireless systems is their potential for
   accommodating device roaming and mobility.  Scalable and efficient
   support of this mobility within Internet protocols can aid in pushing
   native IP services out to the mobile devices.


   Several limitations were identified relating to current specification
   of mobile IPv4 [48].  Primary among these limitations is that
   mechanisms to support redundant home agents and failover are not
   currently defined.  Redundant home agents are required to avoid
   single point of failure, which would require (proprietary)
   extensions.  Additional deficiencies related to lack of route
   optimization, and tunneling and path MTU issues were also identified.
   Due to these limitations there was reluctance to recommend this as a

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   It was recommended to encourage adoption of IPv6 mobility extensions
   [37] to support roaming capabilities in the wireless environment.  IP
   mobility over IPv6 incorporates improvements to address several
   limitations of the IPv4-based mobility.  The ability to use
   autoconfiguration for "care of" address improves robustness and
   efficiency.  Additionally, path MTU is more easily adapted when a
   router forwards to a new "care of" address.

   Building wireless roaming atop IPv6-based mobility may introduce
   IPv4/IPv6 transition issues unique to the mobile environment.  It was
   recommended to add investigation of these issues to the charter of
   the existing IETF Next Generation Transition (ngtrans) working group,
   provided any mobile IP interoperation issues be identified.


   Scalable and widespread authentication, authorization, and accounting
   (AAA) services are critical to the deployment of commercial services
   based on (wireless) mobile IP.  Some work is progressing on
   definition of these standards for IP mobility [26,49].  However, due
   to the pivotal role of these protocols on the ability to deploy
   commercial services, it was recommended to make finalization of these
   AAA standards and investigation of AAA scalability as high

4.5 Recommendations on TCP and Transport Protocols

   The wireless environment and applications place additional
   requirements on transport protocol.  Unique link error and
   performance characteristics, and application sensitivity to
   connection setup and transaction semantics has led to "optimized"
   transports specific to each environment.  These new transports often
   lack robustness found in Internet  transport and place barriers to
   seamless gatewaying to the Internet.  It was felt that better
   education on transport design and cooperation on Internet transport
   evolution could lead to significant improvements.


   It was recommended that the IETF Transport Area (tsv) working group
   document why Internet transport protocols are the way they are.  The
   focus should be on generic transport issues and mechanisms, rather
   than TCP specifics.  This should capture usage and tradeoffs in
   design of specific transport mechanisms (e.g., connection

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   establishment, congestion control, loss recovery strategies, etc.),
   and document some of the history behind transport research in the

   This "entry point" document into transport design is in direct
   support of the recommendations in section 4.1 to foster communication
   and mutual education.  In addition it was deemed critical that the
   Internet community make it very clear that congestion control is not
   optional.  Internet researchers have learned that optimizing for a
   single link or homogeneous environment does not scale.  Early work by
   Jacobson [34,35], standardization of TCP congestion control [5], and
   continuing work within the IETF Endpoint Congestion Management (ecm)
   working group could provide excellent basis for education of wireless
   transport designers.


   It was recommended that the IETF actively solicit input from external
   standards bodies on identifying explicit requirements and in
   assessing inefficiencies in existing transports in support of
   cellular and wireless environments.  This has proven highly effective
   in identifying research topics and in guiding protocol evolution to
   address new operational environments, for instance in cooperation
   with groups doing satellite-based internetworking [4,6].


   It was recommended that the IAB make wireless standards bodies aware
   of the existence, and get them active in, the IETF Transport Area
   (tsv) working group.  This transport "catch all" could provide an
   excellent forum for workers outside the Internet community to propose
   ideas and requirements, and engage in dialog with IESG members prior
   to contributing any formal proposal into the IETF or incurring
   overhead of working group formation.


   Mobile radio environments may often be subject to frequent temporary
   outages.  For example, roaming through an area that is out of range
   of any base station, or disruptions due to base station handoffs.
   This violation of the congestive loss assumption of TCP can have
   severe detrimental effect on transport performance.  It was
   recommended to investigate mechanisms for improving transport
   performance when these non-congestive loss can be detected.  Areas
   for potential research identified include incorporation of "hints" to
   the sender providing Non-Congestive Loss Indication (NCLI) or
   stimulating transmission after link recovery via Source Encourage

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   (SE) message [39].  This likely falls to the auspice of the IETF
   Performance Implications of Link Characteristics (pilc) working


   Many wireless applications require transaction semantics and are
   highly sensitive to connection establishment delays (e.g., WAP).
   However, it is still desirable to efficiently support streaming of
   large bulk transfers too.  It was recommended to investigate
   tradeoffs in supporting these transaction and streaming connections.
   Potential areas for investigation include tradeoffs between minimal
   transaction transport and potential security and denial of service
   (DoS) attacks, mechanisms to piggyback data during connection
   establishment to eliminate round trip delays, or ways for endpoints
   to cooperate in eliminating setup handshake for simple transactions
   while providing switch-over to reliable streaming for bulk transfers.


   It was recommended to look at (TCP) transport improvements specific
   to the wireless and mobile environment.  An example is to investigate
   reattachable transport endpoints.  This could allow for graceful
   recovery of a transport connection after a roaming or mobility event
   results in changes to one or both endpoint identifiers.  Another area
   for potential investigation is to develop targeted uses of D-SACK
   [25].  D-SACK provides additional robustness to reordered packets,
   which may prove beneficial in wireless environment where packets are
   occasionally corrupted.  Higher performance may be attainable by
   eliminating requirements on link-level retransmission maintaining
   in-order delivery within a flow.

4.6 Recommendations on Routing

   Unique routing requirements may be introduced in support of wireless
   systems, especially when viewing the mobile component as an
   autonomous system (AS).


   It was recommended that the IETF Routing Area commence investigation
   of extensions to the BGP protocol [54] to support additional policy
   features available within the ISO IDRP protocol [33].  The range of
   policy control desired includes adopting different identity or
   policies based on current point of attachment, and providing
   flexibility in path selection based on local policy and/or current

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   peer policy.  These features could be used for instance in support of
   requirements established in the Aeronautical Telecommunication
   Network (ATN).


   It was recommended that the IETF Routing Area commence investigation
   of extensions to the BGP protocol [54] to support additional QoS/TOS
   path selection features available within the ISO IDRP protocol [33].
   The range of policies include differentiating service level or path
   selection based on traffic classes.  An example, based on
   Aeronautical Telecommunication Network (ATN) requirements, might be
   differentiating path selection and service between airline control
   and passenger entertainment traffic.

4.7 Recommendations on Mobile Host QoS Support

   Wireless link bandwidth is often scarce (e.g., cellular) and/or
   shared (e.g., IEEE 802.11 WLAN).  Meeting application QoS needs
   requires accommodating these link characteristic, in addition to the
   roaming nature of mobile host.  Specialized support may be required
   from the network layer to meet both link and end-to-end performance


   It was recommended that the IETF Transport Area undertake
   investigation into providing QoS in the last leg of mobile systems.
   That is, between the mobile device and the network access point.
   This type of QoS support might be appropriate where the wireless link
   is the most constrained resource.  A potential solution to
   investigate is to employ an explicit reservation mechanism between
   the mobile host and the access point (e.g., RSVP [13]), while relying
   on resource provisioning or more scalable DiffServ [9] technologies
   within the core.


   It was recommended that the IETF Transport Area undertake
   investigation into end-to-end QoS when the path includes a mixture of
   wireless and wired technologies.  This investigation could focus on
   mechanism to communicate QoS characteristics in cellular network to
   the core network to establish end-to-end QoS guarantees.  An
   alternative investigation is to look into discovery problem of
   assessing current end-to-end performance characteristics, enabling
   for dynamic adaptation by mobile host.

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4.8 Recommendations on Application Mobility

   In a mobile environment with roaming, and mobile host disconnect and
   reconnect at different attachment point it may be desirable to
   recover an incomplete application session.  It was recommended that
   the IRTF investigate application mobility at this level.  The goal is
   to achieve a smooth recovery after a disconnect period; something
   more graceful than a "redial".  Currently there does not appear to be
   sufficient information available within the network stack, this may
   require instantiation of some form of "session" layer.

4.9 Recommendations on TCP/IP Performance Characterization in WAP-like

   WAPF has gone to considerable effort to develop unique transport
   protocol and optimizations due to perception that TCP/IP protocol
   stack is too expensive.  Much of this was predicated on WAP
   requirements to support very low datarate bearer services.  It was
   recommended that members of the IRTF evaluate TCP/IP stack
   performance in WAP-like environment to quantify its behavior and
   applicability.  The focus should include investigation of code and
   memory space requirements, as well as link usage to complete a single
   transaction for current WAP protocols and for both IPv4 and IPv6.
   This work should result in better characterization of TCP/IP
   performance in highly constrained devices and network,
   recommendations to the IETF on protocol enhancements to optimize
   performance in this environment, and recommendations to WAPF on
   suitability of deploying native IP protocols.

4.10 Recommendations on Protocol Encoding

   IETF protocol developments have traditionally taken the approach of
   preferring simple encode/decode and word alignment at the cost of
   some extra bit transmissions.  This overhead may prove too burdensome
   in some bandwidth constrained environments, such as cellular wireless
   and WAP.  Work within the IETF Robust Header Compression (rohc)
   working group may go a long way to reducing some of these detriments
   to Internet protocols deployment.  However, there may be potential
   for additional savings from investigation of alternative encoding of
   common Internet protocols.  It was recommended that members of the
   IRTF evaluate general techniques that can be used to reduce protocol
   "verbiage".  Examples might include payload compression techniques or
   tokenized protocol encoding.

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4.11 Recommendations on Inter-Domain AAA Services

   Commercial roaming and mobility services are likely to require
   exchange of authentication, authorization, and billing services
   spanning multiple domains (service providers).  This introduces
   requirements related to establishing a web or hierarchy of trust
   across multiple autonomous domains.  Standard protocols to specify
   and exchange usage policies and billing information must also be
   established.  Some work is progressing on scoping out the issues and
   a framework [7,64].  However, there are significant issues to be
   solved to enable a scalable, Internet-wide solution.  Due to the
   pivotal role of these protocols on the ability to deploy commercial
   services, it was recommended to make finalization of scalable inter-
   domain AAA as high priority within the IETF.

4.12 Recommendations on Bluetooth

   Bluetooth protocols and devices were originally optimized for a
   narrow application space.  However, there is interest in exploring
   the breadth to which protocol and device access can be extended.  One
   particular area of interest is exploring integration into, or
   gatewaying access to, the Internet.  It was recommended that the IETF
   pursue formation of a joint BOF to assemble experts from the IETF and
   Bluetooth communities to begin exploration of this problem.  This is
   in direct support of the recommendations in section 4.1 to foster
   communication and mutual education.

4.13 Recommendations on Proxy Architecture

   Proxy agents are often deployed to intercept and evaluate protocol
   requests (e.g., web cache, HTTP redirector, filtering firewall) or to
   gateway access between communication domains (e.g., traversing
   bastion host between private network and Internet or gatewaying
   between a cellular service and the Internet).  There are a number of
   potential architectures when contemplating development and deployment
   of one of these proxy agent.  It was recommended that members of the
   IRTF investigate taxonomy of proxy architectures and evaluate their
   characteristics and applicability.  Each type of proxy should be
   characterized, for example, by its effect on Internet end-to-end
   model, and security, scaling, and performance implications.  The
   results of this study can help educate developers and network
   operators on the range of proxy available and recommend solutions
   that are least disruptive to Internet protocols.

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4.14 Recommendations on Justifying IPv6-based Solutions for Mobile /
     Wireless Internet

   IPv6 was strongly recommended to address scaling (see section 4.3)
   and mobility (see section 4.4) issues in the future Internet
   dominated by large numbers of wireless and mobile devices.  It was
   recommended that the IAB draft a formalized justification for these
   recommendations for adoption of IPv6-based solution.  It was believed
   that the "The Case for IPv6" [40] document should form an excellent
   basis for this justification.  In addition, documents highlighting
   architectural and operational pitfalls of continued reliance on IPv4
   and NAT also provide excellent justification [29,31,59].  It was
   deemed urgent to submit these informational documents as inputs to
   other standards bodies (MWIF, 3GPP, 3G.IP), as many decisions are
   being made on Internet protocol adoption and this data could be
   highly influential.

5 Security Considerations

   This workshop did not focus on security.  However, mobility and
   wireless environment introduces additional complexities for security
   and potential attacks to user authentication and privacy.  The
   presentations by Asokan and by Calhoun referenced in section 2
   focused on security mechanisms in currently deployed cellular
   networks and evolution toward 3G cellular and IP networks.
   Discussion on the "walled garden" service model (see section 3.1)
   briefly mentions effects on simplifying security requirements.
   Section 3.3 raises a number of security issues related to wireless
   devices and mobility.  These include alternatives for establishing
   user identity and capabilities, securing network infrastructure from
   attacks, and security associations required for mobile IP and AAA
   operation.  Section 3.7 mentions interoperation issues between
   compression and encryption or tunneling, and finally section 3.9
   highlight potential for proxy agent to be used to offload expensive
   crypto operations.

6 Acknowledgments

   The author would like to thank all of the workshop participants for
   their feedback, encouragement, and patience during the writeup of
   this document.  I would especially like to thank Brian Carpenter for
   prompt responses to questions on the document organization and
   content.  Similarly, Charlie Perkins provided extensive feedback that
   dramatically improved and corrected statements throughout the report.
   Finally, Mikael Degermark, Sally Floyd, Heikki Hammainen, Geoff
   Huston, and Gabriel Montenegro contributed comments and responses to

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7 Bibliography

   [1]  ACIRI.  TCP-Friendly Rate Control.  http://www.aciri.org/tfrc.

   [2]  A. Aggarwal, S. Savage, and T. Anderson.  Understanding the
        Performance of TCP Pacing.  Proceedings of IEEE Infocom 2000,
        March 2000.

   [3]  Allman, M., Floyd, S. and C. Partridge, "Increasing TCP's
        Initial Window", RFC 2414, September 1998.

   [4]  Allman, M., Glover, D. and L. Sanchez, "Enhancing TCP Over
        Satellite Channels using Standard Mechanisms",  RFC 2488,
        January 1999.

   [5]  Allman, M., Paxson, V. and W. Stevens, "TCP Congestion Control",
        RFC 2581, April 1999.

   [6]  Allman, M., Dawkins, S., Glover, D., Griner, J., Tran, D.,
        Henderson, T., Heidemann, J., Touch, J., Kruse, H., Ostermann,
        S., Scott, K. and J. Semke, "Ongoing TCP Research Related to
        Satellites", RFC 2760, February 2000.

   [7]  Arkko, J., "Requirements for Internet-Scale Accounting
        Management", Work in Progress.

   [8]  Bates, T., Chandra, R., Katz, D. and Y. Rekhter, "Multiprotocol
        Extensions for BGP-4", RFC 2283, February 1998.

   [9]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and W.
        Weiss, "An Architecture for Differentiated Services" RFC 2475,
        December 1998.

   [10] Borella, M., et al., "Realm Specific IP: Framework", Work in

   [11] Borella, M., et al., "Realm Specific IP: Protocol
        Specification", Work in Progress.

   [12] Braden, R., "T/TCP -- TCP Extensions for Transactions Functional
        Specification", RFC 1644, July 1994.

   [13] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin,
        "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
        Specification", RFC 2205, September 1997.

   [14] Brim, S., Carpenter, B. and F. Le Faucheur, "Per Hop Behavior
        Identification Codes", RFC 2836, May 2000.

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RFC 3002                 IAB Wireless Workshop             December 2000

   [15] Carpenter, B., Crowcroft, J. and Y. Rekhter, "IPv4 Address
        Behaviour Today", RFC 2101, February 1997.

   [16] Carpenter, B., "Internet Transparency", RFC 2775, February 2000.

   [17] Crawford, M., "Router Renumbering for IPv6", RFC 2894, August

   [18] Croft, B. and J. Gilmore, "Bootstrap Protocol (BOOTP)", RFC 951,
        September 1985.

   [19] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
        Specification", RFC 2460, December 1998.

   [20] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
        2246, January 1999.

   [21] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
        March 1997.

   [22] Everhart, C., Mamakos, L., Ullman, R. and P. Mockapetris, "New
        DNS RR Definitions", RFC 1183, October 1990.

   [23] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
        Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
        HTTP/1.1", RFC 2616, June 1999.

   [24] Floyd, S. and T. Henderson, "The NewReno Modification to TCP's
        Fast Recovery Algorithm", RFC 2582, April 1999.

   [25] Floyd, S., Mahdavi, J., Mathis, M. and M. Podolsky, "An
        Extension to the Selective Acknowledgment (SACK) Option for
        TCP", RFC 2883, July 2000.

   [26] Glass, S., Hiller, T., Jacobs, S. and C. Perkins, "Mobile IP
        Authentication, Authorization, and Accounting Requirements", RFC
        2977, October 2000.

   [27] Gulbrandsen, A. and P. Vixie, "A DNS RR for specifying the
        location of services (DNS SRV)", RFC 2052, October 1996.

   [28] Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service
        Location Protocol, Version 2", RFC 2608, June 1999.

   [29] Hain, T., "Architectural Implications of NAT", RFC 2993,
        November 2000.

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RFC 3002                 IAB Wireless Workshop             December 2000

   [30] Handley, M., Schulzrinne, H., Schooler, E., and J. Rosenberg,
        "SIP: Session Initiation Protocol", RFC 2543, March 1999.

   [31] Holdrege, M. and P. Srisuresh, "Protocol Complications with the
        IP Network Address Translator (NAT)", Work in Progress.

   [32] International Telecommunication Union.  Visual Telephone Systems
        and Equipment for Local Area Networks which provide a Non-
        guaranteed Quality of Service.  Recommendation H.323, May 1996.

   [33] ISO/IEC.  Protocol for Exchange of Inter-Domain Routeing
        Information among Intermediate Systems to support Forwarding of
        ISO 8473 PDUs.  ISO/IEC IS10747, 1993.

   [34] V. Jacobson.  Congestion Avoidance and Control.  Computer
        Communication Review, vol. 18, no. 4 August 1988.

   [35] V. Jacobson.  Modified TCP Congestion Avoidance Algorithm.
        end2end-interest mailing list, April 30, 1990.

   [36] Jacobson, V., Braden, R. and D. Borman, "TCP Extensions for High
        Performance", RFC 1323, May 1992.

   [37] Johnson, D. and C. Perkins, "Mobility Support in IPv6", Work in

   [38] Jonsson, L., et al., "RObust Checksum-based header COmpression
        (ROCCO)", Work in Progress.

   [39] Karn, P., et al., "Advice for Internet Subnetwork Designers",
        Work in Progress.

   [40] King, S., et al., "The Case for IPv6", Work in Progress.

   [41] J. Kulik, R. Coulter, D. Rockwell, and C. Partridge.  Paced TCP
        for High Delay-Bandwidth Networks.  Proceedings of IEEE Globecom
        '99, December 1999.

   [42] Le, K., et al., "Adaptive Header ComprEssion (ACE) for Real-Time
        Multimedia", Work in Progress.

   [43] Mathis, M., Mahdavi, J., Floyd, S. and A. Romanow, "TCP
        Selective Acknowledgment Options", RFC 2018, October 1996.

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RFC 3002                 IAB Wireless Workshop             December 2000

   [44] Mockapetris, P., "Domain Names -- Concepts and Facilities", STD
        13, RFC 1034, November 1987.

   [45] Mockapetris, P., "Domain Names -- Implementation and
        Specification", STD 13, RFC 1035, November 1987.

   [46] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of
        the Differentiated Services Field (DS Field) in the IPv4 and
        IPv6 Headers", RFC 2474, December 1998.

   [47] Partridge, C., Mendez, T. and W. Milliken, "Host Anycasting
        Service", RFC 1546, November 1993.

   [48] Perkins, C., "IP Mobility Support", RFC 2002, October 1996.

   [49] Perkins, C. and P. Calhoun, "AAA Registration Keys for Mobile
        IP", Work in Progress.

   [50] Perkins, C. and D. Johnson, "Route Optimization in Mobile IP",
        Work in Progress.

   [51] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August

   [52] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.

   [53] Ramakrishnan, K. and S. Floyd, "A Proposal to add Explicit
        Congestion Notification (ECN) to IP", RFC 2481, January 1999.

   [54] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
        RFC 1771, March 1995.

   [55] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. and E.
        Lear, "Address Allocation for Private Internets", BCP 5, RFC
        1918, February 1996.

   [56] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote
        Authentication Dial In User Service (RADIUS)", RFC 2138, April

   [57] Schulzrinne, H., Casner, S., Fredrick, R. and V. Jacobson, "RTP:
        A Transport Protocol for Real-Time Applications", RFC 1889,
        January 1996.

   [58] J. Semke, J. Mahdavi, and M. Mathis.  Automatic TCP Buffer
        Tuning.  Proceedings of ACM SIGCOMM '98, September 1998.

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RFC 3002                 IAB Wireless Workshop             December 2000

   [59] Srisuresh, P. and M. Holdrege, "IP Network Address Translator
        (NAT) Terminology and Considerations", RFC 2663, August 1999.

   [60] Srisuresh, P. and K. Egevang, "Traditional IP Network Address
        Translator (Traditional NAT)", Work in Progress.

   [61] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
        H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson,
        "Stream Control Transmission Protocol", RFC 2960, October 2000.

   [62] Thomson, S. and T. Narten, "IPv6 Stateless Address
        Autoconfiguration", RFC 2462, December 1998.

   [63] Touch, J., "TCP Control Block Interdependence", RFC 2140, April

   [64] Vollbrecht, J., et al., "AAA Authorization Framework", Work in

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A Participants

     Juha Ala-Laurila                JUHA.ALA-LAURILA@nokia.com
     Mark Allman                     mallman@grc.nasa.gov
     Alastair Angwin                 angwin@uk.ibm.com
     N. Asokan                       n.asokan@nokia.com
     Victor Bahl                     bahl@microsoft.com
     Fred Baker                      fred@cisco.com
     Pravin Bhagwat                  pravinb@us.ibm.com
     Scott Bradner                   sob@harvard.edu
     Randy Bush                      randy@psg.com
     Pat Calhoun                     Pcalhoun@eng.sun.com
     Brian Carpenter                 brian@icair.org
     Mikael Degermark                micke@cs.arizona.edu
     Sally Floyd                     floyd@aciri.org
     Heikki Hammainen                HEIKKI.HAMMAINEN@NOKIA.COM
     Mark Handley                    mjh@aciri.org
     Bob Hinden                      hinden@iprg.nokia.com
     Christian Huitema               huitema@microsoft.com
     Chih-Lin I                      ci@att.com
     Van Jacobson                    van@packetdesign.com
     Phil Karn                       Karn@qualcomm.com
     John Klensin                    Klensin@JCK.com
     Jerry Lahti                     jerry.lahti@nokia.com
     Allison Mankin                  mankin@isi.edu
     Danny J. Mitzel                 mitzel@iprg.nokia.com
     Gabriel Montenegro              gab@sun.com
     Keith Moore                     moore@cs.utk.edu
     Eric Nordmark                   nordmark@sun.com
     Charles E. Perkins              charliep@iprg.nokia.com
     Jonne Soininen                  jonna.Soininen@nokia.com
     Chris A. Wargo                  cwargo@cnsw.com
     Lars Westberg                   Lars.Westberg@era.ericsson.se
     Lixia Zhang                     lixia@cs.ucla.edu

B Author's Address

   Danny J. Mitzel
   313 Fairchild Drive
   Mountain View, CA 94043

   Phone: +1 650 625 2037
   EMail: mitzel@iprg.nokia.com

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Full Copyright Statement

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