Network Working Group Osama Aboul-Magd Internet Draft Sameh Rabie Document: draft-aboulmagd-trTCM-inprofile-00.txt Category: Informational Nortel Networks September, 2003 Two Rate Three Color Marker for Efficient Handling of In-Profile Packets Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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. 1. Abstract This document describes a two rate three color marker that has been in use for data services including Frame Relay services. This marker can be used for metering per-flow traffic in the emerging IP and L2 VPN services. The marker defined here is different from previously defined markers in the handling and guarantee afforded to the in- profile traffic. Furthermore this marker doesnÆt impose peak rate shaping requirements on customer edge (CE) devices. 2. Conventions used in this document 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]. 3. Introduction The differentiated service defines a quality of service (QoS) architecture for the Internet [3]. Integral component of this architecture are traffic metering and marking. This document Aboul-Magd Expires April 2004 1 Draft-aboulmagd-trTCM-inprofile-00.txt September 2004 describes a two rate three color metering/marker algorithm that is suitable for the differentiated service applications such as IP and L2 VPNs. This algorithm has been in use for data services including Frame Relay Service. The metering/marker defined here is different from those in [4] and [5]. It is different from [4] in that it is a two-rate, three-color marker. In contrast [4] is a single rate marker. It is different from [5] in the way its parameters are defined which allows a better handling of in-profile traffic for predominant service scenarios over a wider range of traffic parameters. Furthermore the algorithm described here eliminates the need for the CE to shape its traffic to a certain peak information rate (PIR) as might be the case for the marker defined in [5] when the value for the peak burst size (PBS) is smaller than that for the committed burst size (CBS). The marker described here operates for both color-blind and color- aware modes as defined in [5] 4. Configuration The operation of the marker is described by two rate values, those are the committed information rate (CIR) and the excess information rate (EIR). Each of CIR and EIR defines the token generation rate of a token bucket with size that is equal to committed burst size (CBS) and excess burst size (EBS) respectively. The CBS and EBS are measured in bytes and must configure to be greater than the expected maximum length of incoming PDU. Both CIR and EIR are measured in bits/s. The CIR and EIR can be set independent of each other. Alternatively CIR and EIR can be linked together by defining a burst duration parameter T, where T=CBS/CIR=EBS/EIR. 5. Metering and Marking The behavior of the meter is defined in terms of its mode and two token buckets, C and E, with rate CIR and EIR respectively and maximum size CBS and EBS. The token buckets C and E are initially (at time 0) full, i.e. the token count Tc(0) = CBS and Te(0) = EBS. Thereafter the token counts Tc is incremented by one CIR times per second up to CBS and the token count Te is incremented by one EIR times per second up to CBS. In the color aware operation it is assumed that the algorithm can recognize the color of the incoming packet (Green, yellow, or red). The color-aware operation of the metering is: When a green packet of size B arrives at time t, then Aboul-Magd Expires April 2004 2 Draft-aboulmagd-trTCM-inprofile-00.txt September 2004 o if Tc(t)- B > 0, the packet is green and Tc(t) is decremented by B, else o if Te(t)- B > 0, the packet is yellow and Te(t) is decremented by B, else o the packet is red When a yellow packet of size B arrives at time t, then o if Te(t)- B > 0, the packet is yellow and Te(t) is decremented by B, else o the packet is red Incoming red packets are not tested against any of the two token buckets and remain red. In the color blind operation the meter assumes that all incoming packets are green. The operation of the meter is similar to that in the color aware operation for green packets. The salient feature of the algorithm described above is that traffic that is within the defined CIR is colored green directly without the need to pass additional conformance tests. This feature is the main differentiator of this algorithm compared to that described in [5] where traffic is marked green after it passes two conformance tests (those for PIR and CIR). In either color blind or color aware modes the need to pass two conformance tests could result in packets being dropped at the PIR token bucket even though they are perfectly within their CIR (in-profile traffic). Furthermore, in the color aware mode of operation, the need to pass two conformance tests could result in yellow traffic starving incoming in-profile green packets. The operation of the algorithm is illustrated in the flow chart below: +---------------------------------+ |periodically every T sec. | | Tc(t+)=MIN(CBS, Tc(t-)+CIR*T) | | Te(t+)=MIN(EBS, Te(t-)+EIR*T) | +---------------------------------+ Packet of size B arrives /----------------\ ---------------->|color-blind mode| | OR |YES +---------------+ | green packet |---->|packet is green| | AND | |Tc(t+)=Tc(t-)-B| | B <= Tc(t-) | +---------------+ \----------------/ Aboul-Magd Expires April 2004 3 Draft-aboulmagd-trTCM-inprofile-00.txt September 2004 | | NO v /----------------\ |color-blind mode| | OR |YES +----------------+ | NOT red packet |---->|packet is yellow| | AND | |Te(t+)=Te(t-)-B | | B <= Te(t-) | +----------------+ \----------------/ | | NO v +---------------+ |packet is red | +---------------+ Figure 1: Traffic Metering/Marking Algorithm In Figure 1, we have X(t-) and X(t+) to indicate the value of a parameter X right before and right after time t. 6. Service Scenarios The described marker can be used to mark an IP packet stream in a service, where different, decreasing levels of assurances (either absolute or relative) are given to packets which are green, yellow, or red. For example, a service may discard all red packets, because they exceeded the peak rate, forward yellow packets as best effort, and forward green packets with low drop probability. The marker could also be used for metering L2 VPN services such as the emerging Ethernet transport over IP networks. 7. Security Considerations The marker/metering algorithm described here has no known security concerns. 8. References 1 Bradner, S., æThe Internet Standards Process -- Revision 3Æ, BCP 9, RFC 2026, October 1996. 2 Bradner, S., æKey words for use in RFCs to Indicate Requirement LevelsÆ, BCP 14, RFC 2119, March 1997 3 Blake, S., et. al., æAn Architecture for Differentiated ServicesÆ, RFC 2475, December 1998. Aboul-Magd Expires April 2004 4 Draft-aboulmagd-trTCM-inprofile-00.txt September 2004 4 Heinanen, J., and Guerin, R., æA Single Rate Three Color MarkerÆ, RFC 2697, September 1999. 5 Heinanen, J., and Guerin, R., æA Two Rate Three Color MarkerÆ, RFC 2698, September 1999. 9. Author's Addresses Osama Aboul-Magd Nortel Networks P.O. Box 3511, Station C Ottawa, ONT, Canada K1Y-4H7 Phone: +1 613 763 5827 E.mail : osama@nortelnetworks.com Sameh Rabie Nortel Networks P.O. Box 3511, Station C Ottawa, ONT, Canada K1Y-4H7 Phone: +1 613 765 2587 E.mail : rabie@nortelnetworks.com Aboul-Magd Expires April 2004 5 Draft-aboulmagd-trTCM-inprofile-00.txt September 2004 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. 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