RFC 2698

A Two Rate Three Color Marker

📅 published September 1999, from ietf

A Two Rate Three Color Marker 🎀

bestie, this is RFC 2698 and it's giving tiny spec, big energy 💅 Here's the title-block tea ☕

  • Series: Network Working Group
  • Authors: J. Heinanen (Telia Finland) and R. Guerin (University of Pennsylvania)
  • Category: Informational
  • Date: September 1999
  • Obsoletes / Updates: the header doesn't list anything this RFC obsoletes or updates 🫶

Status of this Memo ✨

okay so this memo gives info to the Internet community 💖 It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright (C) The Internet Society (1999). All Rights Reserved.

Abstract 🦋

okay this doc defines a Two Rate Three Color Marker (trTCM), which can be used as a component in a Diffserv traffic conditioner [RFC2475, RFC2474]. The trTCM meters an IP packet stream and marks its packets based on two rates, Peak Information Rate (PIR) and Committed Information Rate (CIR), and their associated burst sizes to be either green, yellow, or red. A packet is marked red if it exceeds the PIR. Otherwise it is marked either yellow or green depending on whether it exceeds or doesn't exceed the CIR. main character energy 👑

1. Introduction ✨

so the trTCM meters an IP packet stream and marks each packet green, yellow, or red 🌈 Red means it went over the Peak Information Rate (PIR). Anything else is yellow or green, depending on whether it went over the Committed Information Rate (CIR). It's really useful for ingress policing of a service, where you want to enforce a peak rate separately from a committed rate 🔥

The Meter checks each packet and passes the packet plus the metering result to the Marker:

                        +------------+
                        |   Result   |
                        |            V
                    +-------+    +--------+
                    |       |    |        |
  Packet Stream ===>| Meter |===>| Marker |===> Marked Packet Stream
                    |       |    |        |
                    +-------+    +--------+

The Meter has two modes 🧚 In the Color-Blind mode, the Meter assumes the packet stream is uncolored. In the Color-Aware mode, the Meter assumes some earlier entity already pre-colored the incoming stream so each packet is green, yellow, or red. The details of the pre-coloring process, including how error scenarios are handled and how the Meter figures out 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 based on what the Meter found. The color lives in the DS field [RFC2474] of the packet, coded in a PHB specific way (see section 4 for an example) 💜

A companion doc [RFC2697] describes another three color marker, called a Single Rate Three Color Maker (srTCM), where packets are marked based on a single rate and two burst sizes 🍓

2. Configuration 🎀

the trTCM gets configured by setting its mode and assigning values to four traffic parameters: a Peak Information Rate (PIR) with its associated Peak Burst Size (PBS), and a Committed Information Rate (CIR) with its associated Committed Burst Size (CBS) 💖

The PIR and CIR are measured in bytes of IP packets per second, i.e., they include the IP header but not link specific headers. The PIR must be equal to or greater than the CIR.

The PBS and the CBS and are measured in bytes, and both of them must be configured to be greater than 0. It is recommended that they be configured to be equal to or greater than the size of the largest possible IP packet in the stream. 🫶

3. Metering 🦋

The Meter's behavior is specified in terms of its mode and two token buckets, P and C, with rates PIR and CIR respectively. The maximum size of bucket P is PBS, and the maximum size of bucket C is CBS 🌸

The token buckets P and C start out full at time 0, so Tp(0) = PBS and Tc(0) = CBS. After that, the token count Tp goes up by one PIR times per second, capped at PBS, and the token count Tc goes up by one CIR times per second, capped at CBS ✨

When a packet of size B bytes arrives at time t and the trTCM is in Color-Blind mode, here's the tea:

  • If Tp(t)-B < 0, the packet is red, else
  • if Tc(t)-B < 0, the packet is yellow and Tp is decremented by B, else
  • the packet is green and both Tp and Tc are decremented by B.

When a packet of size B bytes arrives at time t and the trTCM is in Color-Aware mode:

  • If the packet has been precolored as red or if Tp(t)-B < 0, the packet is red, else
  • if the packet has been precolored as yellow or if Tc(t)-B < 0, the packet is yellow and Tp is decremented by B, else
  • the packet is green and both Tp and Tc are decremented by B.

ngl the actual implementation of a Meter doesn't need to be modeled on the formal spec above 🧚

4. Marking 💅

The Marker reflects the metering result by setting the DS field of the packet to a particular codepoint. For the AF PHB [RFC2597], the color can be coded as the drop precedence of the packet 🔥

5. Service Example 🌈

the trTCM can mark an IP packet stream in a service where different, decreasing levels of assurance (either absolute or relative) are given to green, yellow, or red packets 👑 For example, a service may discard all red packets (they went over the peak rate), forward yellow packets as best effort, and forward green packets with a low drop probability 💖

6. Security Considerations 💀

The trTCM has no known security concerns. 😭

7. References 📚

[RFC2697] Heinanen, J. and R. Guerin, "A Single Rate Three Color Marker", RFC 2697, 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.

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 367 GRW 200 South 33rd Street Philadelphia, PA 19104

EMail: guerin@ee.upenn.edu

Copyright (C) The Internet Society (1999). All Rights Reserved.

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Acknowledgement 🌷

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