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draft-aboulmagd-trtcm-inprofile-02.txt --> rfc4115.txt

Network Working Group Osama O. Aboul-Magd
Internet Draft Sameh
Request for Comments: 4115 S. Rabie
Expires: April 2005
Category: Informational Nortel Networks

November 2004
July 2005

A Differentiated Service Two Rate Three Color Two-Rate, Three-Color Marker for with
Efficient
handling Handling of in-Profile Traffic
draft-aboulmagd-trTCM-inprofile-02.txt

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Abstract

This document describes a two rate three color 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
Furthermore, this marker doesnÆt doesn't impose peak rate peak-rate shaping
requirements on customer edge (CE) devices.

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1. Introduction

The differentiated service defines a quality of service quality-of-service (QoS)
architecture for the Internet [RFC2475]. Integral component Two integral components of
this architecture are traffic metering and marking. This document
describes a two rate three color two-rate, three-color metering/marker algorithm that is

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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, two-
rate, three-color marker. In contrast contrast, [RFC2697] is a single
rate single-rate
marker. It is different from [RFC2698] in the way its parameters are defined
defined, which allows a better handling of in-profile traffic for
predominant service scenarios over a wider range of traffic
parameters.

Furthermore

Furthermore, the algorithm described here eliminates the need for the
CE to shape its traffic to a certain peak information rate (PIR) (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 modes, as defined in [RFC2698].

2. Configuration

The operation of the marker is described by two rate values, those
are the values. The
committed information rate (CIR) and the excess information rate
(EIR). Each of CIR and EIR defines define the token generation rate of a token
bucket with size that is equal to committed burst size (CBS) and
excess burst size (EBS) (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. Both The
CIR and EIR are both measured in bits/s. The CIR and EIR can be set
independent
independently of each other. Alternatively Alternatively, the CIR and EIR can be
linked together by defining a burst duration parameter 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 rate the rates, CIR and EIR respectively EIR, respectively,
and maximum size sizes CBS and EBS.

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The token buckets C and E are initially (at time 0) full, i.e. full; i.e., the
token count Tc(0) = CBS and Te(0) = EBS. Thereafter Thereafter, the token counts count
Tc is incremented by one CIR times per second up (up to CBS CBS), and the
token count Te is incremented by one EIR times per second up (up to EBS.
EBS).

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In the color aware operation color-aware operation, it is assumed that the algorithm can
recognize the color of the incoming packet (Green, (green, yellow, or red).
The color-aware operation of the metering is: is described below.

When a green packet of size B arrives at time t, then

o if Tc(t)- B > 0, the packet is green green, and Tc(t) is decremented
by
B, B; else

o if Te(t)- B > 0, the packet is yellow yellow, and Te(t) is decremented
by
B, B; else

o the packet is red red.

When a yellow packet of size B arrives at time t, then

o if Te(t)- B > 0, the packet is yellow yellow, and Te(t) is decremented
by
B, B; else

o the packet is red red.

Incoming red packets are not tested against any of the two token
buckets and remain red.

In the color blind operation color-blind operation, the meter assumes that all incoming
packets are green. The operation of the meter is similar to that in
the color aware color-aware operation for green packets.

The salient feature of the algorithm described above is that traffic
that is
within the defined CIR is colored green directly directly, without the need to
pass additional conformance tests. This feature is the main
differentiator of this algorithm compared to from that described in
[RFC2698] [RFC2698],
where traffic is marked green after it passes two conformance tests
(those for PIR and CIR). In either color blind color-blind or
color aware modes color-aware mode,
the need to pass two conformance tests could result in packets being
dropped at the PIR token bucket even though they are perfectly within
their CIR (in-profile traffic). Furthermore, in the color aware color-aware mode
of operation, the need to pass two conformance tests could result in make
yellow traffic starving starve incoming in-profile green packets.

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The operation of the algorithm is illustrated in the flow chart
below:

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Packet of size
B arrives /----------------\
---------------->|color-blind mode|
| OR |YES +---------------+
| green packet |---->|packet is green|
| AND | |Tc(t+)=Tc(t-)-B|
| B <= Tc(t-) | +---------------+
\----------------/
|
| NO
v
/----------------\
|color-blind mode|
| OR |YES +----------------+
| NOT red packet |---->|packet is yellow|
| AND | |Te(t+)=Te(t-)-B |
| B <= Te(t-) | +----------------+
\----------------/
|
| NO
v
+---------------+
|packet is red |
+---------------+

Figure 1: Traffic Metering/Marking Algorithm

In Figure 1, we have X(t-) and X(t+) to indicate the value of a
parameter X right before and right after time t.

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4. Service Scenario

The described marker can be used to mark an IP packet stream in a
service,
service where different, decreasing levels of assurances (either
absolute or relative) are given to packets which that are green, yellow, or
red. For example, a service may discard all red packets, packets because they
exceeded the service rates, forward yellow packets as best effort,
and forward green packets with low drop probability. The marker
could also be used for metering L2 VPN services such as the emerging
Ethernet transport over IP networks.

5. Security Considerations

Security issues resulting from this document are similar to those
mentioned in RFC[2697] [RFC2697] and RFC[2698].

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6. Informative References

[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated Service",
RFC 2475, December 1998.

[RFC2697] Heinanen, J. and R. Guerin, "A Single Rate Three Color
Marker", RFC 2697, September 1999.

[RFC2698] Heinanen, J. and R. Guerin, "A Two Rate Three Color
Marker", RFC 2698, September 1999.

[RFC3932] Alvestrand, H., "The IESG and RFC Editor Documents:
Procedures", BCP 92, RFC 3932, October 2004.

Authors' Addresses

Osama Aboul-Magd
Nortel Networks
3500 Carling Ave
Ottawa, ON K2H8E9
Email: osama@nortelnetworks.com
EMail: osama@nortel.com

Sameh Rabie
Nortel Networks
3500 Carling Ave
Ottawa, ON K2H8E9
Email: rabie@nortelnetworks.com
EMail: rabie@nortel.com

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