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diff --git a/doc/rfc/rfc2697.txt b/doc/rfc/rfc2697.txt new file mode 100644 index 0000000..bfa6882 --- /dev/null +++ b/doc/rfc/rfc2697.txt @@ -0,0 +1,339 @@ + + + + + + +Network Working Group J. Heinanen +Request for Comments: 2697 Telia Finland +Category: Informational R. Guerin + University of Pennsylvania + September 1999 + + + A Single Rate Three Color Marker + +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 (1999). All Rights Reserved. + +Abstract + + This document defines a Single Rate Three Color Marker (srTCM), which + can be used as component in a Diffserv traffic conditioner [RFC2475, + RFC2474]. The srTCM meters a traffic stream and marks its packets + according to three traffic parameters, Committed Information Rate + (CIR), Committed Burst Size (CBS), and Excess Burst Size (EBS), to be + either green, yellow, or red. A packet is marked green if it doesn't + exceed the CBS, yellow if it does exceed the CBS, but not the EBS, + and red otherwise. + +1. Introduction + + The Single Rate Three Color Marker (srTCM) meters an IP packet stream + and marks its packets either green, yellow, or red. Marking is based + on a Committed Information Rate (CIR) and two associated burst sizes, + a Committed Burst Size (CBS) and an Excess Burst Size (EBS). A + packet is marked green if it doesn't exceed the CBS, yellow if it + does exceed the CBS, but not the EBS, and red otherwise. The srTCM + is useful, for example, for ingress policing of a service, where only + the length, not the peak rate, of the burst determines service + eligibility. + + + + + + + + + + +Heinanen & Guerin Informational [Page 1] + +RFC 2697 A Single Rate Three Color Marker September 1999 + + + The Meter meters each packet and passes the packet and the metering + result to the Marker: + + +------------+ + | Result | + | V + +-------+ +--------+ + | | | | + Packet Stream ===>| Meter |===>| Marker |===> Marked Packet Stream + | | | | + +-------+ +--------+ + + The Meter operates in one of two modes. In the Color-Blind mode, the + Meter assumes that the packet stream is uncolored. In the Color- + Aware mode the Meter assumes that some preceding entity has pre- + colored the incoming packet stream so that each packet is either + green, yellow, or red. The details of the pre-coloring process, + including handling of error scenarios, and how the Meter determines + the color of a pre-colored packet are DS domain specific and outside + the scope of this document. + + The Marker (re)colors an IP packet according to the results of the + Meter. The color is coded in the DS field [RFC2474] of the packet in + a PHB specific manner (see section 4 for an example). + + A companion document [RFC2698] describes another three color marker, + called a Two Rate Three Color Maker (trTCM), where packets are marked + based on two rates and two burst sizes. + +2. Configuration + + The srTCM is configured by setting its mode and by assigning values + to three traffic parameters: a Committed Information Rate (CIR), a + Committed Burst Size (CBS), and an Excess Burst Size (EBS). + + The CIR is measured in bytes of IP packets per second, i.e., it + includes the IP header, but not link specific headers. + + The CBS and the EBS and are measured in bytes. The CBS and EBS must + be configured so that at least one of them is larger than 0. It is + recommended that when the value of the CBS or the EBS is larger than + 0, it is larger than or equal to the size of the largest possible IP + packet in the stream. + + + + + + + + +Heinanen & Guerin Informational [Page 2] + +RFC 2697 A Single Rate Three Color Marker September 1999 + + +3. Metering + + The behavior of the Meter is specified in terms of its mode and two + token buckets, C and E, which both share the common rate CIR. The + maximum size of the token bucket C is CBS and the maximum size of the + token bucket E is EBS. + + The token buckets C and E are initially (at time 0) full, i.e., the + token count Tc(0) = CBS and the token count Te(0) = EBS. Thereafter, + the token counts Tc and Te are updated CIR times per second as + follows: + + o If Tc is less than CBS, Tc is incremented by one, else + + o if Te is less then EBS, Te is incremented by one, else + + o neither Tc nor Te is incremented. + + When a packet of size B bytes arrives at time t, the following + happens if the srTCM is configured to operate in the Color-Blind + mode: + + o If Tc(t)-B >= 0, the packet is green and Tc is decremented by B + down to the minimum value of 0, else + + o if Te(t)-B >= 0, the packets is yellow and Te is decremented by B + down to the minimum value of 0, else + + o the packet is red and neither Tc nor Te is decremented. + + When a packet of size B bytes arrives at time t, the following + happens if the srTCM is configured to operate in the Color-Aware + mode: + + o If the packet has been precolored as green and Tc(t)-B >= 0, the + packet is green and Tc is decremented by B down to the minimum + value of 0, else + + o If the packet has been precolored as green or yellow and if + Te(t)-B >= 0, the packets is yellow and Te is decremented by B + down to the minimum value of 0, else + + o the packet is red and neither Tc nor Te is decremented. + + Note that according to the above rules, marking of a packet with a + given color requires that there be enough tokens of that color to + accommodate the entire packet. Other marking policies are clearly + possible. The above policy was chosen in order guarantee a + + + +Heinanen & Guerin Informational [Page 3] + +RFC 2697 A Single Rate Three Color Marker September 1999 + + + deterministic behavior where the volume of green packets is never + smaller than what has been determined by the CIR and CBS, i.e., + tokens of a given color are always spent on packets of that color. + + The actual implementation of a Meter doesn't need to be modeled + according to the above formal specification. + +4. Marking + + The Marker reflects the metering result by setting the DS field of + the packet to a particular codepoint. In case of the AF PHB + [RFC2597], the color can be coded as the drop precedence of the + packet. + +5. Service Example + + The srTCM can be used to mark a 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 + both the committed and excess burst sizes, forward yellow packets as + best effort, and forward green packets with a low drop probability. + +6. Security Considerations + + The srTCM has no known security concerns. + +7. References + + [RFC2698] Heinanen, J. and R. Guerin, "A Two Rate Three Color + Marker", RFC 2698, September 1999. + + [RFC2597] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, + "Assured Forwarding PHB Group", RFC 2597, June 1999. + + [RFC2474] 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. + + [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. + and W. Weiss, "An Architecture for Differentiated + Services", RFC 2475, December 1998. + + + + + + + + +Heinanen & Guerin Informational [Page 4] + +RFC 2697 A Single Rate Three Color Marker September 1999 + + +8. Authors' Addresses + + Juha Heinanen + Telia Finland, Inc. + Myyrmaentie 2 + 01600 Vantaa, Finland + + EMail: jh@telia.fi + + + Roch Guerin + University of Pennsylvania + Department of Electrical Engineering, Rm 376 GRW + 200 South 33rd Street + Philadelphia, PA 19104 + + EMail: guerin@ee.upenn.edu + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Heinanen & Guerin Informational [Page 5] + +RFC 2697 A Single Rate Three Color Marker September 1999 + + +9. Full Copyright Statement + + Copyright (C) The Internet Society (1999). 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. + + + + + + + + + + + + + + + + + + + +Heinanen & Guerin Informational [Page 6] + |