As per Relevance of the word september, we have this rfc below:
Network Working Group J.
Request for Comments: 2697 Telia
Category: Informational R.
University of
September 1999
A Single Rate Three Color
Status of this
This memo provides information for the Internet community. It
not specify an Internet standard of any kind. Distribution of
memo is unlimited
Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved
This document defines a Single Rate Three Color Marker (srTCM),
can be used as component in a Diffserv traffic conditioner [RFC2475,
RFC2474]. The srTCM meters a traffic stream and marks its
according to three traffic parameters, Committed Information
(CIR), Committed Burst Size (CBS), and Excess Burst Size (EBS), to
either green, yellow, or red. A packet is marked green if it doesn'
exceed the CBS, yellow if it does exceed the CBS, but not the EBS
and red otherwise
1.
The Single Rate Three Color Marker (srTCM) meters an IP packet
and marks its packets either green, yellow, or red. Marking is
on a Committed Information Rate (CIR) and two associated burst sizes
a Committed Burst Size (CBS) and an Excess Burst Size (EBS).
packet is marked green if it doesn't exceed the CBS, yellow if
does exceed the CBS, but not the EBS, and red otherwise. The
is useful, for example, for ingress policing of a service, where
the length, not the peak rate, of the burst determines
eligibility
Heinanen & Guerin Informational [Page 1]
RFC 2697 A Single Rate Three Color Marker September 1999
The Meter meters each packet and passes the packet and the
result to the Marker
+------------+
| Result |
|
+-------+ +--------+
| | | |
Packet Stream ===>| Meter |===>| Marker |===> Marked Packet
| | | |
+-------+ +--------+
The Meter operates in one of two modes. In the Color-Blind mode,
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
green, yellow, or red. The details of the pre-coloring process
including handling of error scenarios, and how the Meter
the color of a pre-colored packet are DS domain specific and
the scope of this document
The Marker (re)colors an IP packet according to the results of
Meter. The color is coded in the DS field [RFC2474] of the packet
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
based on two rates and two burst sizes
2.
The srTCM is configured by setting its mode and by assigning
to three traffic parameters: a Committed Information Rate (CIR),
Committed Burst Size (CBS), and an Excess Burst Size (EBS).
The CIR is measured in bytes of IP packets per second, i.e.,
includes the IP header, but not link specific headers
The CBS and the EBS and are measured in bytes. The CBS and EBS
be configured so that at least one of them is larger than 0. It
recommended that when the value of the CBS or the EBS is larger
0, it is larger than or equal to the size of the largest possible
packet in the stream
Heinanen & Guerin Informational [Page 2]
RFC 2697 A Single Rate Three Color Marker September 1999
3.
The behavior of the Meter is specified in terms of its mode and
token buckets, C and E, which both share the common rate CIR.
maximum size of the token bucket C is CBS and the maximum size of
token bucket E is EBS
The token buckets C and E are initially (at time 0) full, i.e.,
token count Tc(0) = CBS and the token count Te(0) = EBS. Thereafter
the token counts Tc and Te are updated CIR times per second
follows
o If Tc is less than CBS, Tc is incremented by one,
o if Te is less then EBS, Te is incremented by one,
o neither Tc nor Te is incremented
When a packet of size B bytes arrives at time t, the
happens if the srTCM is configured to operate in the Color-
mode
o If Tc(t)-B >= 0, the packet is green and Tc is decremented by
down to the minimum value of 0,
o if Te(t)-B >= 0, the packets is yellow and Te is decremented by
down to the minimum value of 0,
o the packet is red and neither Tc nor Te is decremented
When a packet of size B bytes arrives at time t, the
happens if the srTCM is configured to operate in the Color-
mode
o If the packet has been precolored as green and Tc(t)-B >= 0,
packet is green and Tc is decremented by B down to the
value of 0,
o If the packet has been precolored as green or yellow and
Te(t)-B >= 0, the packets is yellow and Te is decremented by
down to the minimum value of 0,
o the packet is red and neither Tc nor Te is decremented
Note that according to the above rules, marking of a packet with
given color requires that there be enough tokens of that color
accommodate the entire packet. Other marking policies are
possible. The above policy was chosen in order guarantee
Heinanen & Guerin Informational [Page 3]
RFC 2697 A Single Rate Three Color Marker September 1999
deterministic behavior where the volume of green packets is
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
according to the above formal specification
4.
The Marker reflects the metering result by setting the DS field
the packet to a particular codepoint. In case of the AF
[RFC2597], the color can be coded as the drop precedence of
packet
5. Service
The srTCM can be used to mark a packet stream in a service,
different, decreasing levels of assurances (either absolute
relative) are given to packets which are green, yellow, or red.
example, a service may discard all red packets, because they
both the committed and excess burst sizes, forward yellow packets
best effort, and forward green packets with a low drop probability
6. Security
The srTCM has no known security concerns
7.
[RFC2698] Heinanen, J. and R. Guerin, "A Two Rate Three
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 (
Field) in the IPv4 and IPv6 Headers", RFC 2474,
1998.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z
and W. Weiss, "An Architecture for
Services", RFC 2475, December 1998.
Heinanen & Guerin Informational [Page 4]
RFC 2697 A Single Rate Three Color Marker September 1999
8. Authors'
Juha
Telia Finland, Inc
Myyrmaentie 2
01600 Vantaa,
EMail: jh@telia.
Roch
University of
Department of Electrical Engineering, Rm 376
200 South 33rd
Philadelphia, PA 19104
EMail: guerin@ee.upenn.
Heinanen & Guerin Informational [Page 5]
RFC 2697 A Single Rate Three Color Marker September 1999
9. Full Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Heinanen & Guerin Informational [Page 6]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
RFC documents can be found at I.E.T.F.
Relevance System Copyright © 2002 Spectrum WorldResearch
other technical nosh by ServerMasters Corporation
collaboration of BobX
