A Differentiated Service Two-Rate, Three-Color Marker with Efficient Handling of in-Profile Traffic
RFC 4115
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RFC - Informational
(July 2005; No errata)
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2013-03-02
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RFC 4115 (Informational)
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Jon Peterson
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Network Working Group O. Aboul-Magd
Request for Comments: 4115 S. Rabie
Category: Informational Nortel Networks
July 2005
A Differentiated Service Two-Rate, Three-Color Marker with
Efficient Handling of in-Profile Traffic
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 (2005).
IESG Note
This RFC is not a candidate for any level of Internet Standard. The
IETF disclaims any knowledge of the fitness of this RFC for any
purpose and in particular notes that the decision to publish is not
based on IETF review for such things as security, congestion control,
or inappropriate interaction with deployed protocols. The RFC Editor
has chosen to publish this document at its discretion. Readers of
this document should exercise caution in evaluating its value for
implementation and deployment. See RFC 3932 for more information.
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 of the in-profile traffic.
Furthermore, this marker doesn't impose peak-rate shaping
requirements on customer edge (CE) devices.
1. Introduction
The differentiated service defines a quality-of-service (QoS)
architecture for the Internet [RFC2475]. Two integral components of
this architecture are traffic metering and marking. This document
describes a two-rate, three-color metering/marker algorithm that is
Aboul-Magd & Rabie Informational [Page 1]
RFC 4115 Efficient Handling of in-Profile Traffic July 2005
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 [RFC2697]
and [RFC2698]. It is different from [RFC2697] in that it is a two-
rate, three-color marker. In contrast, [RFC2697] is a single-rate
marker. It is different from [RFC2698] 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 [RFC2698] 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 [RFC2698].
2. Configuration
The operation of the marker is described by two rate values. The
committed information rate (CIR) and the excess information rate
(EIR). CIR and EIR define 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 the incoming PDU. The
CIR and EIR are both measured in bits/s. The CIR and EIR can be set
independently of each other. Alternatively, the CIR and EIR can be
linked together by defining a burst duration parameter, T, where
T=CBS/CIR=EBS/EIR.
3. Metering and Marking
The behavior of the meter is defined in terms of its mode and two
token buckets, C and E, with the rates, CIR and EIR, respectively,
and maximum sizes 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 count
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
EBS).
Aboul-Magd & Rabie Informational [Page 2]
RFC 4115 Efficient Handling of in-Profile Traffic July 2005
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 described below.
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