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.
AbstractThis 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.
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.
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. RFC2597], the color can be coded as the drop precedence of the packet. [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.
Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.