Network Working Group F. Baker Internet-Draft Cisco Systems Expires: January 20, 2003 July 22, 2002 Recommended Packet Marking Policy draft-ietf-ieprep-packet-marking-policy-01 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 January 20, 2003. 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 [3]. Baker Expires January 20, 2003 [Page 1] Internet-Draft Document July 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 within corporate LANs and ISP backbones is virtually unknown. This clashes with user perceptions, for three very good reasons. o 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 throughput rates are artificially limited, or because of access network design trade-offs. o Other characteristics, such as database design on web servers (which may create contention points, e.g. in filestore), and configuration of firewalls and routers, often look 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 Differentiated Services concepts The reader must be familiar with the principles of the Differentiated Services Architecture [8]. However, we recapitulate key concepts here so save searching. 1.2.1 Queue or Class A queue or class is a data structure that holds traffic that is awaiting transmission. The traffic will be delayed while in the queue, possibly due to lack of bandwidth, or because it is low in priority. 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. Baker Expires January 20, 2003 [Page 2] Internet-Draft Document July 2002 A simple model of a queuing system, however, is a set of data structures for packet data, which we will call queues or classes, and a mechanism for selecting the next packet from among them, which we call a scheduler. 1.2.1.1 Priority Queue A priority queuing system is a combination of a set of queues and a scheduler that empties them in priority sequence. When asked for a packet, the scheduler inspects the first queue, and if there 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 which allows vehicles in the high occupancy vehicle lane to pass, is an example of a priority queuing system; the high occupancy vehicle lane represents the "queue" having priority. 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 variation in delay 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 that 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 [27][26] or WRR [28], 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" or AQM 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 Baker Expires January 20, 2003 [Page 3] Internet-Draft Document July 2002 Random Early Detection [25], in which a queue is assigned a minimum and maximum threshold, and the queuing algorithm maintains a moving average of the queue depth. While the mean queue depth exceeds the maximum threshold, all arriving traffic is dropped. While the mean queue depth exceeds the minimum threshold but not the maximum threshold, a randomly selected subset of arriving traffic is marked or dropped. This marking or dropping of traffic is intended to communicate with the sending system, causing its congestion avoidance algorithms to kick in. As a result of this behavior, it is reasonable to expect that TCP's cyclic behavior is desynchronized, and the mean queue depth (and therefore delay) should normally approximate the minimum threshold. A variation of the algorithm is applied in Assured Forwarding [11], in which the behavior aggregate consists of traffic with multiple DSCP marks, which are intermingled in a common queue. Different minima and maxima are configured for the several DSCPs separately, such that traffic which exceeds a stated rate at ingress is more likely to be dropped or marked than traffic which was within its contracted rate. 1.2.3 Conditioning of traffic Additionally, at the first router in a network that a packet crosses, arriving traffic may be measured, and dropped or marked according to a policy, or perhaps shaped on network ingress as in [23]. This may be used to bias feedback loops, such as is done in Assured Forwarding [11], or to limit the amount of traffic in a system, as is done in Expedited Forwarding [19]. Such measurement procedures are collectively referred to as "traffic conditioners". 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. Half of these values are earmarked for standardized services, and half of them are available for local definition. 1.2.5 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 January 20, 2003 [Page 4] Internet-Draft Document July 2002 1.3 Key Service concepts While Differentiated Services is a general architecture that may be used to implement a variety of services, three fundamental services have been defined and characterized for general use. These are basic service for elastic traffic, the Assured Forwarding service, and the Expedited Forwarding service for real-time (inelastic) traffic. The terms "elastic" and "real-time" are defined in RFC 1633 [2] section 3.1, as a way of understanding broad brush application requirements. This document should be reviewed to obtain a broad understanding of the issues in quality of service, just as RFC 2475 [8] should be reviewed to understand the data plane architecture used in today's Internet. 1.3.1 Best Effort Service The basic services applied to any class of traffic are those described in [7] and [6]. Best Effort Service may be summarized as "I will accept your packets", with no further guarantees. Packets in transit may be lost, reordered, duplicated, or delayed at random. Generally, networks are engineered to limit this behavior, but changing traffic loads can push any network into such a state. Application traffic in the internet is expected to be "elastic" in nature. By this, we mean that the receiver will detect loss or variation in delay in the network and provide feedback such that the sender adjusts its transmission rate to approximate available capacity. For basic best effort service classes, we provide a single DSCP value to identify the traffic, a queue or class to store it, and active queue management to protect the network from it and to limit delays. The interesting thing is that by giving that queue a higher minimum rate than its measured arrival rate, we can effectively limit the deleterious effects of congestion on a given class of traffic, transfering them to another class that is perhaps better able to absorb the impact or is considered to be of lower value to the network administration. So, for example, if it is important to service database exchange or transaction traffic in a timely fashion, isolating the traffic into a queue and giving it a relatively high minimum rate will accomplish that. 1.3.2 Assured Forwarding (AF) The Assured Forwarding [11] service is explicitly modeled on Frame Relay's DE flag or ATM's CLP capability, and is intended for networks which (as those do) offer average-rate SLAs. This is an enhanced Baker Expires January 20, 2003 [Page 5] Internet-Draft Document July 2002 Best Effort service; traffic is expected to be "elastic" in nature. By this, we mean that the receiver will detect loss or variation in delay in the network and provide feedback such that the sender adjusts its transmission rate to approximate available capacity. For such classes, we provide a multiple DSCP values (two or three, perhaps more using local values) to identify the traffic, a common queue or class to store the aggregate, and active queue management to protect the network from it and to limit delays. We meter traffic as it enters the network, and traffic is variously marked depending on the arrival rate of the aggregate. The premise is that it is normal for users to occasionally use more capacity than their contract stipulates, perhaps up to some bound. However, if traffic must be lost or marked to manage the queue, this excess traffic will be marked or lost first. 1.3.3 Expedited Forwarding (EF) Expedited Forwarding [19] was originally proposed as a way to implement a virtual wire, and can be used in such a manner. It is an enhanced best effort service: traffic remains subject to loss due to line errors and reordering during routing changes. However, using queuing techniques, the probability of delay or variation in delay is minimized. For this reason, it is generally used as the way to carry voice, and perhaps video. Voice and video are inelastic "real-time" applications - they send packets at the rate the codec produces them, regardless of availability of capacity. As such, this service has the potential to disrupt or congest a network if not controlled. It also has the potential for abuse. To protect the network, at minimum one must police traffic at various points to ensure that the design of a queue is not over-run, and then the traffic must be given a low delay queue (often using priority, although it is asserted that a rate-based queue can do this) to ensure that variation in delay is not an issue, to meet application needs. There is controversy regarding the place of signaling. Call Admission Control, including call refusal when policy thresholds are crossed, can assure high quality communication by ensuring the availability of bandwidth to carry a load. For this purpose, RSVP [4][13] was designed. However, there is concern with the scalability [5] of that solution, and in large networks, aggregation [15] of sessions is appropriate. Baker Expires January 20, 2003 [Page 6] Internet-Draft Document July 2002 2. Specified Traffic Classes Figure A shows eleven classes of traffic that are commonly specified in enterprise networks or on access links. It is not mandatory to configure any of them; 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 or mark | | | AF12 | 001100 | | general data service| AF13 <= AF12 | | | AF13 | 001110 | | | <= AF11,| | | | | | possible guaranteed minimum rate| | | | | | possible guaranteed maximum rate| +-----+------+--------+-----------+---------------------+--------------+ |AF2 | AF21 | 010010 | RFC 2597 | ERP Database access,| drop or 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 or 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 or mark | | | AF42 | 100100 | | associated voice | AF43 <= AF42 | | | AF43 | 100110 | | | <= AF41,| | | | | | possible guaranteed minimum rate| | | | | | possible guaranteed maximum rate| | | | | | Bandwidth Signaling| +-----+------+--------+-----------+---------------------+--------------+ |IP |Class6| 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|Class4| | section 4.2.2 | AQM | +-----+------+--------+-----------+---------------------+--------------+ Baker Expires January 20, 2003 [Page 7] Internet-Draft Document July 2002 +=====+======+====================+=====================+==============+ |PHB | DSCP | DSCP | Reference | Intended protocols | Configuration| +=====+======+========+===========+=====================+==============+ | |Class3| 011000 | RFC 2474 | SIP, | minimum rate | |Telephony | | section 4.2.2 H.245/H.225 |Deep Queue AQM| |Signaling | | | | | |voice/video | | | | | +-----+------+--------+-----------+---------------------+--------------+ | |Class2| 010000 | RFC 2474 | SNMP | minimum rate | |Network | | section 4.2.2 | AQM | |Management | | | | | +-----+------+--------+-----------+---------------------+--------------+ | |class1| 001000 |Internet II|User-selected service| AQM | |Scavenger | | QBSS | | | +-----+------+--------+-----------+---------------------+--------------+ | |class0| 000000 | RFC 2474 | Unspecified traffic | minimum rate | |Default | | section 4.1 | AQM | +=====+======+========+===========+=====================+==============+ Figure A: Summary of specified Differentiated Services classes 2.1 Voice on IP The voice traffic class serves RTP voice. It is specified in [19]. The fundamental service offered to voice traffic is best effort service up to a specified upper bound with nominal delay. Operation is in some respects similar to an ATM CBR VC. The ATM VC is guaranteed its bandwidth, and if it stays within the negotiated rate it experiences nominal loss and delay. EF traffic has a similar guarantee. 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 variation in delay. When used to give preferential service, the preferred systems or sessions must be authenticated during the process of resource assignment [12][22][16][17]. They may be given preferential access in whatever manner is appropriate. Baker Expires January 20, 2003 [Page 8] Internet-Draft Document July 2002 2.2 File Transfer Service The File Transfer traffic class serves applications which run over TCP [1] or a transport with a consistent congestion avoidance procedure [9][10], 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, although one cannot definitively say that all FTP transfers are moving data in bulk. The PHB is specified in [11]. The fundamental service offered to file transfer 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 Explicit Congestion Notification [14] or random loss to implement active queue management [6], 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 traffic conditioning passes traffic in the class up to some specified threshold marked AF11, additional traffic up to some secondary threshold marked as AF12, and potentially passes additional traffic marked AF13. 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. When used to give preferential service, the preferred systems or sessions must be authenticated, and ingress policing increases the drop or mark probability of any authorized traffic, it must increase the drop or mark probability of all unauthorized traffic. 2.3 Human-response Applications The human response traffic class serves applications which run over TCP [1] or a transport with a consistent congestion avoidance procedure [9][10], 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 [11]. 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 Explicit Congestion Notification [14] or Baker Expires January 20, 2003 [Page 9] Internet-Draft Document July 2002 random loss to implement active queue management [6], 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. When used to give preferential service, the preferred systems or sessions must be authenticated, and ingress policing increases the drop or mark probability of any authorized traffic, it must increase the drop or mark probability of all unauthorized traffic. 2.4 Mission Specific and Critical Applications The mission-specific traffic class serves applications which run over TCP [1] or a transport with a consistent congestion avoidance procedure [9][10], 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 [11]. The fundamental service offered to mission critical 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 Explicit Congestion Notification [14] or random loss to implement active queue management [6], 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. When used to give preferential service, the preferred systems or sessions must be authenticated, and ingress policing increases the drop or mark probability of any authorized traffic, it must increase the drop or mark probability of all unauthorized 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 [4]. 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 [11]. 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 Baker Expires January 20, 2003 [Page 10] Internet-Draft Document July 2002 delays that exceed its framing interval. It can be assumed, however, to have been initially transmitted in a manner roughly comparable to [23]. As such, active queue management [6] serves primarily to deal with extreme cases; ingress traffic conditioning 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. When used to give preferential service, the preferred systems or sessions must be authenticated during the process of resource assignment [12][22][16][17]. They may be given preferential access in whatever manner is appropriate. 2.6 IP Routing Protocols The IP Routing traffic class serves IP Routing Applications such as BGP or OSPF. It is specified in [7]. 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 to hundreds of milliseconds. By placing it into a separate queue or class to minimize loss, the routing it supports is helped to converge. Typical configurations use Explicit Congestion Notification [14] or random loss to implement active queue management [6], and may impose a minimum or maximum rate. Preferential access is undefined for this traffic class. 2.7 Streaming Video The streaming video traffic class serves applications like Windows Media Player or RealAudio. These may use standard or proprietary bulk transfer protocols, using TCP as a transport or application- specific transports built on UDP, for buffering prior to playout. The service model is specified in [7]. 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 Explicit Congestion Notification [14] or random loss to implement active queue management [6], and may impose a minimum or maximum rate. Baker Expires January 20, 2003 [Page 11] Internet-Draft Document July 2002 Preferential access is undefined for this traffic class. 2.8 Telephony Signaling The Telephony Signaling traffic class serves network control applications like SIP and H.245/H.225 when used to route Voice on IP, Video on IP, and related applications. It is specified in [7]. 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 Explicit Congestion Notification [14] or random loss to implement active queue management [6], 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. Preferential access is undefined for this traffic class. 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 [7]. 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 [6], to maximize the utility of network management applications while protecting the network in the event of an overload. Preferential access is undefined for this traffic class. 2.10 Scavenger class The scavenger traffic class serves applications which run over TCP [1] or a transport with a consistent congestion avoidance procedure [9][10], and which the user is willing to accept service without guarantees. It is specified in [20]. The fundamental service offered to the scavenger traffic class is Baker Expires January 20, 2003 [Page 12] Internet-Draft Document July 2002 best effort service. By placing it into a separate queue or class, it may be treated in a manner consistent with a specific service level agreement. Typical configurations use Explicit Congestion Notification [14] or random loss to implement active queue management [6]. It generally does not impose a minimum or maximum rate, although it could. Preferential access is undefined for this traffic class. 2.11 Default traffic class The default traffic class serves applications which have not been otherwise specified, but which run over TCP [1] or a transport with a consistent congestion avoidance procedure [9][10]. It is specified in [7]. 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 Explicit Congestion Notification [14] or random loss to implement active queue management [6], and may impose a minimum or maximum rate on the queue. Preferential access is undefined for this traffic class. Baker Expires January 20, 2003 [Page 13] Internet-Draft Document July 2002 3. Security Considerations This document discusses policy, and describes a common policy configuration, 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. A well-known flaw applies when bandwidth is reserved or enabled for a service (for example, voice transport) and another service or an attacking traffic stream uses it. This possibility is inherent in diffserv technology, which depends on appropriate packet markings. When bandwidth reservation or a priority queuing system is used in a vulnerable network, the use of a scheme such as RSVP Policy Marking [12] and RSVP Identity [16] is important. To the author's knowledge, there is no technical way to respond to an unauthenticated data stream using service that it is not intended to use, and such is the nature of the Internet. Baker Expires January 20, 2003 [Page 14] Internet-Draft Document July 2002 4. Acknowledgements The author acknowledges a great many inputs, most notably from Bruce Davie, Dave Oran. Kimberly King and Alistair Munroe each did a thorough proof-reading, and the document is better for it. Baker Expires January 20, 2003 [Page 15] Internet-Draft Document July 2002 Normative References [1] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [2] Braden, B., Clark, D. and S. Shenker, "Integrated Services in the Internet Architecture: an Overview", RFC 1633, June 1994. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [4] Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [5] Baker, F., Krawczyk, J. and A. Sastry, "RSVP Management Information Base using SMIv2", RFC 2206, September 1997. [6] Braden, B., Clark, D., Crowcroft, J., Davie, B., Deering, S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G., Partridge, C., Peterson, L., Ramakrishnan, K., Shenker, S., Wroclawski, J. and L. Zhang, "Recommendations on Queue Management and Congestion Avoidance in the Internet", RFC 2309, April 1998. [7] 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. [8] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [9] Allman, M., Paxson, V. and W. Stevens, "TCP Congestion Control", RFC 2581, April 1999. [10] Floyd, S. and T. Henderson, "The NewReno Modification to TCP's Fast Recovery Algorithm", RFC 2582, April 1999. [11] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, "Assured Forwarding PHB Group", RFC 2597, June 1999. [12] Herzog, S., "RSVP Extensions for Policy Control", RFC 2750, January 2000. [13] Bernet, Y., "Format of the RSVP DCLASS Object", RFC 2996, November 2000. [14] Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of Baker Expires January 20, 2003 [Page 16] Internet-Draft Document July 2002 Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [15] Baker, F., Iturralde, C., Le Faucheur, F. and B. Davie, "Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC 3175, September 2001. [16] Herzog, S., "Signaled Preemption Priority Policy Element", RFC 3181, October 2001. [17] Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore, T., Herzog, S. and R. Hess, "Identity Representation for RSVP", RFC 3182, October 2001. [18] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M., Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and S. Waldbusser, "Terminology for Policy-Based Management", RFC 3198, November 2001. [19] 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. [20] , "QBone Scavenger Service (QBSS) Definition", Internet2 Technical Report Proposed Service Definition, March 2001. Baker Expires January 20, 2003 [Page 17] Internet-Draft Document July 2002 Informative References [21] Durham, D., Boyle, J., Cohen, R., Herzog, S., Rajan, R. and A. Sastry, "The COPS (Common Open Policy Service) Protocol", RFC 2748, January 2000. [22] Bernet, Y. and R. Pabbati, "Application and Sub Application Identity Policy Element for Use with RSVP", RFC 2872, June 2000. [23] Bonaventure, O. and S. De Cnodder, "A Rate Adaptive Shaper for Differentiated Services", RFC 2963, October 2000. [24] Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie, K., Herzog, S., Reichmeyer, F., Yavatkar, R. and A. Smith, "COPS Usage for Policy Provisioning (COPS-PR)", RFC 3084, March 2001. [25] Floyd, S. and V. Jacobson, "Random Early Detection Gateways for Congestion Avoidance", IEEE/ACM Transactions on Networking , August 1993. [26] Zhang, L., "Virtual Clock: A New Traffic control Algorithm for Packet Switching Networks", ACM SIGCOMM 1990, September 1990. [27] Keshav, S., "On the Efficient Implementation of Fair Queueing", Internetworking: Research and Experiences Vol 2, September 1991. [28] Katevenis, M., Sidiropoulos, S. and C. Courcoubetis, "Weighted Round-Robin Cell Multiplexing in a General Purpose ATM Switch Chip", IEEE JSAC Vol. 9, No. 8, October 1991. [29] "International Emergency Preparedness Scheme", ITU E.106, March 2000. [30] "Service Description for an International Emergency Multimedia Service (Draft)", ITU-T F.706, August 2001. Baker Expires January 20, 2003 [Page 18] Internet-Draft Document July 2002 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 January 20, 2003 [Page 19] Internet-Draft Document July 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. 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Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Baker Expires January 20, 2003 [Page 20]