Brian's paper on DiffServ confirms the fact that prioritization is
part of the standard. Here are the two relevant quotes:
"In the original design of IP [33], a byte known as the “type of
service (TOS) octet” was reserved in the header of every packet.
This was defined to contain two important fields: a three-bit
“precedence” value and three TOS bits. The precedence was intended
as a simple priority marker, where priority 0 got the worst
treatment and priority 7 got the best." (p. 1480)
"The Diffserv working group has taken the approach that a few
fundamental PHBs should be standardized early. These should derive
from some existing experience (primarily from limited deployment and
experimentation with use of the IP precedence field to select
forwarding behaviors) and might be implemented using a variety of
specific mechanisms. The PHBs standardized so far are as follows...
"• Class selector behaviors: here seven DSCP values run from 001 000
to 111 000 and are specified to select up to seven behaviors, each
of which has a higher probability of timely forwarding than its
predecessor. Experts will note that the default behavior plus
the class selectors exactly mirror the original eight IP
Precedence values." (p. 1487)
This is very straightforward.
RB
On 9/3/2010 1:06 PM, Brian E Carpenter wrote:
Richard,
Diffserv deals with multiple different queuing disiplines, which may or may not be priority based. Please read RFC 2475 and if
you like, B.E. Carpenter and K. Nichols, Differentiated Services in the Internet, Proc. IEEE, 90 (9) (2002) 1479-1494.
Brian
On 2010-09-04 07:57, Richard Bennett wrote:
DiffServ is a prioritization scheme, Brian, how can you say it's not?
IntServ is a reservation scheme, and DiffServ attempts to provide
desired PHBs in practice by sorting packets into priority queues and
invoking appropriate Link Layer facilities, which are in most cases
priority-based, such as 802.11e traffic classes.
What on earth could the value of DSCPs be if they didn't map to traffic
classes in the data link?
RB
Brian E Carpenter <brian.e.carpenter@xxxxxxxxx> wrote:
Russ,
It has been consistently hard to explain that diffserv is not a
prioritisation scheme, even within the technical community, let
alone to the regulators and the media. I think your comments as
quoted are as good as we can expect from journalists.
It should be a matter of concern to all of us here that the US FCC
isn't confused into regulating the technology. It would set a bad
precedent for regulators in other countries. I am making no comment
as to whether they should regulate carrier's charging practices; that's
entirely a national matter that shouldn't concern the IETF in any way.
Regards
Brian Carpenter
On 2010-09-03 05:47, Russ Housley wrote:
I want the whole community to be aware of the comments that I made to
the press yesterday. Clearly, these comments do not represent IETF
consensus in any way. They are my opinion, and the reporter was told to
express them as my opinion.
One thing that I said was not captured quite right. The article says:
"With services that require certain speeds to operate smoothly, such as
Internet telephony, calls are given precedence over TV, Housley said."
I actually said that DiffServ can be used to make sure that traffic
associated with applications that require timely delivery, like voice
and video, to give preference over traffic associated with applications
without those demands, like email.
The whole article is copied below, and it is online here:
http://www.nationaljournal.com/njonline/tc_20100902_7144.php
Russ
--
Richard Bennett
Senior Research Fellow
Information Technology and Innovation Foundation
Washington, DC
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