RFC 2697 (rfc2697) - Page 2 of 6

A Single Rate Three Color Marker

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 [RFC 2474] of the packet in
   a PHB specific manner (see section 4 for an example).

   A companion document [RFC 2698] 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