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I hope
folks have submitted comments on the TX flow-chart on page
48
or
Necdet you have caught this?
One
amusing sequence is:
If MP
TX is less than CIR, Then if MP TX is available, Then mark the packet
OUT-OF-PROFILE
Boy,
did MP packet get into the wrong queue !!
raj
Bob,
You are right. We need to have more detail on this in the normative section
(9.3) of the standard.
Thanks.
Necdet
RDLove wrote:
Necdet, your response to Raj provides an
opportunity to remind everyone that although pseudo-code may be an excellent
way to get some idea of how standards compliant hardware could work, it is
an exemplary implementation only, and is in an informative, not normative
standard, which is where it belongs. Necdet, I don't find any fault in
your pointing to the pseudo-code to show how things might work.
However, it is vital that the IEEE 802.17 standard has a normative portion
that precisely and comprehensively defines standard based behavior for all
compliant hardware. I expect we will need the equivalent of state
machine diagrams and tables to accomplish this vital
function. Best regards, Robert D. Love
Chair,
Resilient Packet Ring Alliance
President, LAN Connect Consultants
7105 Leveret Circle Raleigh, NC 27615
Phone:
919 848-6773 Mobile: 919 810-7816
email: rdlove@xxxxxxxx
Fax: 208 978-1187
----- Original Message -----
Sent: Wednesday, March 06, 2002 2:39
PM
Subject: Re: [RPRWG] Single and dual
transit buffer MACs Raj,
If you look at the psuedo code at Annex H
page 247 line 3:
UpdatedEveryClockCycle(Station * sPtr)
{
// tokenOctets is
decremented by 1 for every LP/eMP octet that is transmitted by the client.
// A packet is sent to completion, why is the below check here?
if
((sPtr->addRateCongestion < sPtr->allowRateCongestion) &&
(sPtr->fwdRate + sPtr->addRate + sPtr->rate_iMP <
MAX_LRATE - sPtr->reservedRate) &&
... )
sPtr->addRateOk = TRUE; // true means OK to send client packets
This check ensures that there is enough BW at the outgoing link for the
reserved traffic, otherwise client will not be able to add eMP or LP
packets to the ring (this will reduce the advertised fair rate as well).
This will ensure that there is enough BW reserved on the link.
Please let me know if you have any questions or comments.
Thanks.
Necdet
Raj Sharma wrote:
I have some concern with
the way in which co-existence of Single Transit Buffer (STB) MAC and
Dual Transit Buffer (DTB) MACs on the same ring has been approached in
draft 0. I thought I voice my concerns to the working group on the
reflector to enable some dialog in resolving this concern while I also
file my comments.
I think the best place to start would be
at Clause 9.3, page 70, lines 3 and 4 which is: "If a ring consists of mixed RPR MACs
(single and dual transit buffer nodes), the fairness scheme will
needto interact without
disadvantaging any other node on the ring."
First disadvantage stems from the special accommodations to be
made in the DTB MACs to support performance requirements while using STB
MAC at other nodes. This requirement is stipulated further down in the
same Clause 9.3, page 70, lines 11 through 13. This stipulates that DTB MAC requires a rate shaper to throttle ring
outgoing rate to no more than 95% of the link rate. The only way a
loss-less MAC (as stipulated in 5.3.2, page 33, line 41) can do this is
to buffer frames when instantaneous rates exceed 95%. Further, if such
traffic shaper is classless than HP priority traffic could be subjected
to further buffering in this traffic shaper leading to contradiction of
clause 3.1, which requires HP traffic to have no more transit delay than
one frame-time through transit nodes.In other words defining a RPR standard
to accommodate STB MAC is not free of cost in terms of implementation and complexity in
the standard.
Raj
Colleagues,Draft
0.1 has been up on the RPR web for a week now, and I have yet to see
any significantdialog on the
issues that have been outlined in the draft by the editors. (I also
have notreceived any formal
comments from RPR WG members.) Please note that there is
onlyabout a week left to go in
the comment period, and about ten days to the meeting, so
Istrongly urge all concerned
parties to start their comments about these issues now.Best
regards,- Tom AlexanderChief Editor, RPR
WG
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