[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00 01

Network Working Group                                           F. Baker
Internet-Draft                                             Cisco Systems
Expires: December 20, 2002                                 June 21, 2002


                   Recommended Packet Marking Policy
               draft-ietf-ieprep-packet-marking-policy-00

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 20, 2002.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This paper summarizes a recommended correlation of applications to
   Differentiated Service Code Points.  There is no intrinsic
   requirement that individual DSCPs correspond to given applications,
   but as a policy it is useful if they can be applied consistently.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [2].







Baker                   Expires December 20, 2002               [Page 1]


Internet-Draft                  Document                       June 2002


1. Introduction

   This paper summarizes a recommended correlation of applications to
   Differentiated Service Code Points.  There is no intrinsic
   requirement that individual DSCPs correspond to given applications,
   but as a policy it is useful if they can be applied consistently.

1.1 Expected use in the network

   In the Internet today, corporate LANs and ISP WANs are generally not
   heavily utilized - they are commonly 10% utilized at most.  For this
   reason, congestion, loss, and variation in delay and within corporate
   and ISP backbones is virtually unknown.  This clashes with ser
   community perceptions, for three very good reasons.

   o  It has not always been thus, and will not always be thus.  The
      industry moves through cycles of bandwidth boom and bandwidth
      bust, depending on prevailing market conditions and the periodic
      deployment of new bandwidth-hungry applications.

   o  In access networks, the state is often different.  This may be
      because rates are artificially limited, or because of access
      network design trade-offs.

   o  Other characteristics, such as database design on web servers, and
      configuration of firewalls and routers, often looks externally
      like a bandwidth limitation.

   The intent of this document is to provide a consistent marking
   strategy so that it can be configured and put into service on any
   link which finds itself congested, typically access links.

1.2 Key Diffserv concepts

   Someone seeking a deep understanding of the Differentiated Services
   Architecture [6] would do well to read it.  However, we recapitulate
   key concepts here so save searching.

1.2.1 Queue or Class

   A queue or class is a data structure which holds traffic which is
   being subjected to delay due to lack of bandwidth.  There are a
   number of ways to implement a queue; in some of these, it is more
   natural to discuss "classes in a queuing system" rather than "a set
   of queues and a scheduler".  In the literature, as a result, the
   concepts are used somewhat interchangeably.

   A simple model of a queuing system, however, is a set of data



Baker                   Expires December 20, 2002               [Page 2]


Internet-Draft                  Document                       June 2002


   structures for packet data, which we will call queues or classes, and
   a mechanism for selecting the next packet from among them.

1.2.1.1 Priority Queue

   A priority queuing system is a combination of a set of queues and a
   scheduler which empties them in priority sequence.  When asked for a
   packet, the scheduler inspects the first queue, and if theer is data
   present returns a packet from that queue.  Failing that, it inspects
   the second queue, and so on.  A freeway onramp with a stoplight for
   one lane but allowing vehicles in the high occupancy vehicle lane to
   pass is an example of a priority queue.

   In a priority queuing system, a packet in the highest priority queue
   will experience a readily calculated delay - it is proportional to
   the amount of data remaining to be serialized when the packet arrived
   plus the volume of the data already queued ahead of it in the same
   queue.  The technical reason for using a priority queue relates
   exactly to this fact: it limits jitter and delay, and should be used
   for traffic which has that requirement.

1.2.1.2 Rate Queues

   Similarly, a rate-based queuing system is a combination of a set of
   queues and a scheduler which empties each at a specified rate.  An
   example of a rate based queuing system is a road intersection with a
   stoplight - the stoplight acts as a scheduler, giving each lane a
   certain opportunity to pass traffic through the intersection.

   In a rate-based queuing system, such as WFQ or WRR, the delay that a
   packet in any given queue will experience is dependant on the
   parameters and occupancy of its queue and the parameters and
   occupancy of the queues it is competing with.  A queue whose traffic
   arrival rate is much less than the rate at which it lets traffic
   depart will tend to be empty, and packets in it will experience
   nominal delays.  A packet whose arrival rate approximates or exceeds
   its departure rate will tend to be full, and packets in it will
   experience greater delay.  Such a scheduler can impose a minimum
   rate, a maximum rate, or both, on any queue it touches.

1.2.2 Active Queue Management

   Active queue management is a generic name for any of a variety of
   procedures that use packet dropping or marking to manage the depth of
   a queue.  The canonical example of such a procedure is RED93, in
   which a queue is assigned a minimum and maximum threshold, and the
   queuing algorithm maintains a moving average of the queue depth.
   When the mean queue depth exceeds the maximum threshold, all traffic



Baker                   Expires December 20, 2002               [Page 3]


Internet-Draft                  Document                       June 2002


   is marked or dropped; when the mean queue depth exceeds the minimum
   threshold, a randomly selected subset if marked or dropped.  This is
   intended to communicate with the system emitting the traffic, causing
   its congestion avoidance algorithms to kick in.

1.2.3 Policing of traffic

   Additionally, at the first router in a network that a acket crosses,
   arriving traffic may be measured, and dropped or marked according to
   a policy.  This may be used to bias feedback loops, such as is done
   in AF [9], or to limit the amount of traffic in a system, as is done
   in EF [11].

1.2.4 Differentiated Services Code Point (DSCP)

   The DSCP is a number in the range 0..63, which is placed into an IP
   packet to mark it according to the class of traffic it belongs in.

1.3 Per Hop Behavior (PHB)

   In the end, the facilities just described are combined to form a
   specified set of characteristics for handling different kinds of
   traffic, depending on the needs of the application.  This document
   seeks to identify useful traffic aggregates and specify what PHB
   should be applied to them.


























Baker                   Expires December 20, 2002               [Page 4]


Internet-Draft                  Document                       June 2002


2. Specified Traffic Classes

    Figure A shows eleven classes of traffic that are commonly specified
   in enterprise networks or on access links.  None of these is
   mandatory for configuration; common experience is that a small subset
   is useful in any given network configuration.  This specification
   recommends that if such a service is deployed, it be deployed in a
   manner consistent with this table.

   +=====+=======+====================+=====================+==============+
   |PHB  | DSCP  | DSCP   | Reference | Intended protocols  | Configuration|
   +=====+=======+========+===========+=====================+==============+
   |EF   | EF    | 101110 | RFC 3246  | Interactive Voice   |RSVP Admission|
   |     |       |        |           |                     |Priority queue|
   +-----+-------+--------+-----------+---------------------+--------------+
   |AF1  | AF11, | 001010 | RFC 2597  | Bulk transfers, web,| drop/mark    |
   |     | AF12, | 001100 |           | general data service| AF13 <= AF12 |
   |     | AF13  | 001110 |           |                     |      <= AF11,|
   |     |       |        |           |    possible guaranteed minimum rate|
   |     |       |        |           |    possible guaranteed maximum rate|
   +-----+-------+--------+-----------+---------------------+--------------+
   |AF2  | AF21, | 010010 | RFC 2597  | Database access,    | drop/mark    |
   |     | AF22, | 010100 |           | transaction services| AF23 <= AF22 |
   |     | AF23  | 010110 |           | interactive traffic |      <= AF21,|
   |     |       |        |           |    possible guaranteed minimum rate|
   |     |       |        |           |    possible guaranteed maximum rate|
   +-----+-------+--------+-----------+---------------------+--------------+
   |AF3  | AF31, | 011010 | RFC 2597  | Locally defined     | drop/mark    |
   |     | AF32, | 011100 |           | mission-critical    | AF33 <= AF32 |
   |     | AF33  | 011110 |           |       applications  |      <= AF31,|
   |     |       |        |           |    possible guaranteed minimum rate|
   |     |       |        |           |    possible guaranteed maximum rate|
   +-----+-------+--------+-----------+---------------------+--------------+
   |AF4  | AF41, | 100010 | RFC 2597  | Interactive video,  | drop/mark    |
   |     | AF42, | 100100 |           | associated voice    | AF43 <= AF42 |
   |     | AF43  | 100110 |           |                     |      <= AF41,|
   |     |       |        |           |    possible guaranteed minimum rate|
   |     |       |        |           |    possible guaranteed maximum rate|
   |     |       |        |           |                 Bandwidth Signaling|
   +-----+-------+--------+-----------+---------------------+--------------+
   |IP   |Class 6| 110000 | RFC 2474  | BGP, OSPF, etc      | minimum rate |
   |Routing      |        | section 4.2.2                   |Deep Queue AQM|
   +-----+-------+--------+-----------+---------------------+--------------+
   |Streaming    | 100000 | RFC 2474  | Often proprietary   | minimum rate |
   |Video|Class 4|        | section 4.2.2                   | AQM          |
   +-----+-------+--------+-----------+---------------------+--------------+





Baker                   Expires December 20, 2002               [Page 5]


Internet-Draft                  Document                       June 2002


   +=====+=======+====================+=====================+==============+
   |PHB  | DSCP  | DSCP   | Reference | Intended protocols  | Configuration|
   +=====+=======+========+===========+=====================+==============+
   |     |Class 3| 011000 | RFC 2474  | SIP, H.323, etc     | minimum rate |
   |Telephony    |        | section 4.2.2                   |Deep Queue AQM|
   |Signaling    |        |           |                     |              |
   |voice/video  |        |           |                     |              |
   +-----+-------+--------+-----------+---------------------+--------------+
   |     |Class 2| 010000 | RFC 2474  | SNMP                | minimum rate;|
   |Network      |        | section 4.2.2                   | AQM          |
   |Management   |        |           |                     |              |
   +-----+-------+--------+-----------+---------------------+--------------+
   |     |class 1| 001000 |Internet II|User-selected service| AQM          |
   |Scavenger    |        |    usage  |                     |              |
   +-----+-------+--------+-----------+---------------------+--------------+
   |     |class 0| 000000 | RFC 2474  | Unspecified traffic | minimum rate |
   |Default      |        | section 4.1                     | AQM          |
   +=====+=======+========+===========+=====================+==============+

   Figure A: Summary of specified diffserv classes

2.1 Voice on IP

   The voice traffic class serves RP voice.  It is specified in [11].

   The fundamental service offered to voice traffic is best effort
   service up to a specified upper bound with nominal delay.  It is in
   many respects similar to an ATM CBR VC; the circuit is guaranteed its
   bandwidth, and if it stays within the negotiated rate it experiences
   nominal loss and delay.

   Typical configurations negotiate the use of Voice on IP using
   protocols such as SIP and RSVP.  When a user has been authorized to
   send voice traffic, this admission procedure has verified that data
   rates will be within the capacity of the network that it will use.
   Since RTP voice does not respond to loss or marking in any
   substantive way, the network must police at ingress to ensure that
   the voice traffic stays within its negotiated bounds.  Having thus
   assured a predictable input rate, the network may use a priority
   queue to ensure nominal delay and jitter.

2.2 File Transfer Applications

   The File Transfer traffic class serves applications but which run
   over TCP [1][7][7] or a transport with a consistent congestion
   avoidance procedure, and normally drive as high a data rate as they
   can obtain over a long period of time.  The FTP protocol is a common
   example.  The PHB is specified in [9].



Baker                   Expires December 20, 2002               [Page 6]


Internet-Draft                  Document                       June 2002


   The fundamental service offered to mission critical traffic is best
   effort service with a specified minimum rate.  One must assume that
   this class will consume any available capacity, and on congested
   links may experience queuing delay or loss.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.  In queues, the probability of loss of AF11 traffic may not
   exceed the probability of loss of AF12 traffic, which in turn may not
   exceed the probability of loss of AF13 traffic.  Ingress policing
   passes traffic in the class up to some specified threshold marked
   AF11, additional traffic up to some secondary threshold marked as
   AF32, and potentially passes additional traffic marked AF33.  In such
   a case, if one network customer is driving significant excess and
   another seeks to use the link, any losses will be experienced by the
   high rate user, causing him to reduce his rate.

2.3 Human-response Applications

   The human response traffic class serves applications but which run
   over TCP [1][7][7] or a transport with a consistent congestion
   avoidance procedure, and serve transaction, database access, or
   interactive protocols.  Such applications might include telnet,
   common ERP applications, instant messaging, or other applications
   which hold a user waiting until they respond.  The PHB is specified
   in [9].

   The fundamental service offered to human response traffic is best
   effort service with a specified minimum rate.  The rate should be
   specified significantly in excess of actual measured rates, in order
   to ensure that this traffic experiences only nominal delay or loss.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.  In queues, the probability of loss of AF21 traffic may not
   exceed the probability of loss of AF22 traffic, which in turn may not
   exceed the probability of loss of AF23 traffic.

2.4 Mission Specific and Critical Applications

   The mission-specific traffic class serves applications but which run
   over TCP [1][7][7] or a transport with a consistent congestion
   avoidance procedure, and serve needs the network administrator deems
   to need special support.  For example, in a banking network, it might
   support electronic banking protocols.  The PHB is specified in [9].

   The fundamental service offered to mission critical traffic is best
   effort service with a specified minimum rate.  The rate should be



Baker                   Expires December 20, 2002               [Page 7]


Internet-Draft                  Document                       June 2002


   specified significantly in excess of actual measured rates, in order
   to ensure that this traffic experiences only nominal delay or loss.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.  In queues, the probability of loss of AF31 traffic may not
   exceed the probability of loss of AF32 traffic, which in turn may not
   exceed the probability of loss of AF33 traffic.

2.5 Network Multimedia (video)

   The Network Multimedia traffic class serves applications that carry
   RTP data streams whose rate has been negotiated with the network
   using a protocol such as RSVP [3].  If the mean rate is conceived as
   Bc/frame interval and the difference between the mean and peak rate
   is Be/frame interval, the first Bc packets in a frame are marked
   AF41, the next Be packets are marked AF42, and any additional packets
   may be summarily dropped, or marked AF43 and subjected to loss in any
   but a queue of nominal depth.  This PHB is specified in [9].

   The fundamental service offered to network multimedia traffic is best
   effort service with controlled rate and delay.  This traffic does not
   respond to loss or marking, and can be severely compromise by loss or
   delays that exceed its framing interval.  It can be assumed, however,
   to have been initially transmitted in a manner roughly comparable to
   [12].  As such, active queue management [4] serves primarily to deal
   with extreme cases; ingress shaping or policing is depended on to
   ensure rate compliance.  In queues, the probability of loss of AF41
   traffic may not exceed the probability of loss of AF42 traffic, which
   in turn may not exceed the probability of loss of AF43 traffic if
   any.

2.6 IP Routing Protocols

   The IP Routing traffic class serves IP Routing Applications such as
   BGP or OSPF.  It is specified in [5].

   The fundamental service offered to routing traffic is best effort
   service with minimal loss, even at the cost of delays on the order of
   tens of milliseconds.    By placing it into a separate queue or
   class, it may be ensured minima or maxima consistent with a specific
   service level agreement.  By placing it into a separate queue or
   class, the routing it supports is helped to converge.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.




Baker                   Expires December 20, 2002               [Page 8]


Internet-Draft                  Document                       June 2002


2.7 Streaming Video

   The streaming video traffic class serves applications like Windows
   Media Player or RealAudio.  These may use proprietary protocols, or
   may use TCP.  It is specified in [5].

   The fundamental service offered to streaming video is best effort
   service.  By placing it into a separate queue or class, it may be
   ensured minima or maxima consistent with a specific service level
   agreement.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.

2.8 Telephony Signaling

   The Telephony Signaling traffic class serves network control
   applications like SIP and H.323 when used to route Voice on IP, Video
   on IP, and related applications.  It is specified in [5].

   The fundamental service offered to Telephony Signaling traffic is
   best effort service with minimize loss.  The reason for this is to
   maximize the speed of such routing, and avoid the poor user
   experience that results from loss of control traffic.  By placing it
   into a separate queue or class, it may be ensured minima or maxima
   consistent with a specific service level agreement.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4], and may impose a minimum or maximum
   rate.  The AQM parameters are specified in such a manner as to permit
   relatively deep queues to form temporarily.

2.9 Network Management

   The management traffic class serves applications that are necessary
   to manage the network, such as SNMP servers, but which implement no
   congestion avoidance procedure.  It is specified in [5].

   The fundamental service offered to the network traffic class is best
   effort service with minimization of loss.  By placing it into a
   separate queue or class, it may be ensured minima or maxima
   consistent with a specific service level agreement.

   Typical configurations use random loss to implement active queue
   management [4], to maximize the utility of network management
   applications while protecting the network in the event of an
   overload.



Baker                   Expires December 20, 2002               [Page 9]


Internet-Draft                  Document                       June 2002


2.10 Scavenger class

   The scavenger traffic class serves applications which run over TCP
   [1][7][7] or a transport with a consistent congestion avoidance
   procedure, and which the user is willing to accept service without
   guarantees.  It is specified in [4].

   The fundamental service offered to the scavenger traffic class is
   best effort service.  By placing it into a separate queue or class,
   it may be ensured minima or maxima consistent with a specific service
   level agreement.

   Typical configurations use ECN [10] or random loss to implement
   active queue management [4].  It generally does not impose a minimum
   or maximum rate.

2.11 Default traffic class

   The default traffic class serves applications which have not been
   otherwise specified, but which run over TCP [1][7][7] or a transport
   with a consistent congestion avoidance procedure.  It is specified in
   [5].

   The fundamental service offered to the default traffic class is best
   effort service with active queue management to limit over-all delay.
   By placing it into a separate queue or class, it may be ensured
   minima or maxima consistent with a specific service level agreement.

   Typical configurations use ECN [10] or random loss to implement
   [4]active queue management [4], and may impose a minimum or maximum
   rate on the queue.




















Baker                   Expires December 20, 2002              [Page 10]


Internet-Draft                  Document                       June 2002


3. Reflexive DSCP Policy

   In reviewing the specific use of the Differentiated Services
   Architecture for supporting the Internet Emergency Preparedness
   System, we found what we believe is a general issue.  This is that
   even though a client or peer can connect to a server or peer with a
   predictable DSCP value, the response does not have a predictable DSCP
   value.  We consider the issues, and recommend an approach to
   application policy regarding the DSCP.

    Figure 1 presents a connection being placed between two applications
   across a differentiated services network.

          . . . .                       . . . .                    . . . .
      .         .           .            .             .            .
    .  Client      .      .                .          .     Server    .
   .  /----------/         .     .  /------------/  .       . /---------------/.
   .      Router -----/----- Router Router ----/----- Router          .
    .             .       .                .        .                 .
      .         .           .            .            .             .
          . . . .                       . . . .                    . . . .

   Figure 1: Connection across a network

   A behavior aggregate originated in part by a certain client toward a
   given server in a remote network may have certain application
   requirements, such as requiring service appropriate to an ERP
   application, video stream, or voice.  One application may use
   different aggregates for different purposes, and therefore have
   different requirements.  So the application may not be able to tell,
   a priori, with what DSCP it should use or respond.

   In addition, DSCPs have local significance in the Differentiated
   Services Architecture.  It is possible and perhaps likely that a
   behavior aggregate might use different code points in different
   networks.

   There are a number of possible approaches to this issue.  The
   simplest, which we fear is currently standard in Differentiated
   Services hosts, is to simply select a default value, such as "always
   make TCP applications use AF11".  For some applications, such as
   voice (EF), this approach is appropriate, but for many it is not.

3.1 Default DSCP policy in a responder

   When a system accepts sessions initiated from another system, and
   there is no specific local policy, the responder SHOULD use the same
   DSCP Group as its request.  Thus, if a TCP SYN arrives using any of



Baker                   Expires December 20, 2002              [Page 11]


Internet-Draft                  Document                       June 2002


   AF11, AF12, or AF13, the TCP SYN-ACK and subsequent messages SHOULD
   use AF11 as the DSCP.  When in doubt as to the set of DSCP code
   points comprising a DSCP Group, it SHOULD respond with exactly the
   same DSCP.

   There has been interest of late in changing the quality of service
   behavior for different portions of the same session, such as on a
   per-URL basis.  The requester could initiate this.  Thus, if the DSCP
   received on one TCP segment differs from the TCP used on a prior TCP
   segment in a session, the new DSCP SHOULD be reflected unless local
   policy prevents this.

   One way to implement this requires the receiving transport (TCP,
   SCTP, etc) to save the received DSCP and use an API to determine the
   correct responding DSCP from a configuration file.  The configuration
   file lists the 64 possible DSCP values and the correct response.  In
   most cases, the two SHOULD be the same, but the twelve AFxy code
   points map to AFx1.  Local policy MAY update this mapping.

3.2 Application-directed DSCP policy

   The originator of a session, which is to say the application that
   opens it, SHOULD normally select the DSCP value used.  This, of
   course, needs to be consistent with local network policy, and may be
   dictated entirely by that policy.

   The application would do this through an API, ideally one that maps
   the application to a DSCP value through local administrative policy.
   Thus, the API could set the DSCP for signaling of voice calls to a
   specific value, such as AF31.  It would be better, though, if the API
   were to set it to a key word such as "VoiceSignaling" or
   "DatabaseAccess", and enable the network administration to interpret
   the key word to an appropriate code point.  One way to implement this
   would be for the API code to look the key word up in a file or an
   LDAP Policy.

   It is possible for the responding application to use this same API.
   For example, separate policies might apply to database records of one
   type and database records of another type, something that only the
   database access application could determine.  It is also possible for
   the application exchange to communicate a desired DSCP, and the
   responding application to use the API accordingly.  In such a case,
   the application exchange MUST specify the key word rather than the
   specific DSCP, as it cannot know the applicable policy in the
   responder's network.






Baker                   Expires December 20, 2002              [Page 12]


Internet-Draft                  Document                       June 2002


4. Security Considerations

   This document discusses policy, and describes a recommended default
   policy, for the use of a Differentiated Services Code Point by
   transports and applications.  If implemented as described, it should
   ask the network to do nothing that the network has not already
   allowed.  If that is the case, no new security issues should arise
   from the use of such a policy.

   It is possible, however, for the policy to be applied incorrectly, or
   for another policy to be applied, which would be incorrect in the
   network.  In that case, a policy issue exists which the network must
   detect, assess, and deal with.  This is a known security issue in any
   network dependent on policy-directed behavior.





































Baker                   Expires December 20, 2002              [Page 13]


Internet-Draft                  Document                       June 2002


5. Acknowledgements

   The author acknowledges a great many inputs, omst notably from Bruce
   Davie, Dave Oran, and Rei Atarashi.















































Baker                   Expires December 20, 2002              [Page 14]


Internet-Draft                  Document                       June 2002


Normative References

   [1]   Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
         September 1981.

   [2]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

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

   [4]   Howard, L., "An Approach for Using LDAP as a Network
         Information Service", RFC 2307, March 1998.

   [5]   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.

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

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

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

   [9]   Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, "Assured
         Forwarding PHB Group", RFC 2597, June 1999.

   [10]  Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of
         Explicit Congestion Notification (ECN) to IP", RFC 3168,
         September 2001.

   [11]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, J.,
         Courtney, W., Davari, S., Firoiu, V. and D. Stiliadis, "An
         Expedited Forwarding PHB (Per-Hop Behavior)", RFC 3246, March
         2002.











Baker                   Expires December 20, 2002              [Page 15]


Internet-Draft                  Document                       June 2002


Informative References

   [12]  Bonaventure, O. and S. De Cnodder, "A Rate Adaptive Shaper for
         Differentiated Services", RFC 2963, October 2000.

   [13]  "International Emergency Preparedness Scheme", ITU E.106, March
         2000.

   [14]  "Service Description for an International Emergency Multimedia
         Service (Draft)", ITU-T F.706, August 2001.


Author's Address

   Fred Baker
   Cisco Systems
   1121 Via Del Rey
   Santa Barbara, CA  93117
   US

   Phone: +1-408-526-4257
   Fax:   +1-413-473-2403
   EMail: fred@cisco.com




























Baker                   Expires December 20, 2002              [Page 16]


Internet-Draft                  Document                       June 2002


Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















Baker                   Expires December 20, 2002              [Page 17]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/