[Tsvwg] Comments on draft-morita-tsvwg-pps

["Geib, Ruediger" <[e-mail]>]

Hello Naotaka,

I think that pps is a good 
idea. Having not to maintain QoS signaling 
state in a backbone router is a pretty 
good thing to do.

Some comments on contents:

Section 4 suggests two stage monitoring 
of end-system behaviour. I agree that abuse 
must be prevented at the source. You don't 
talk of signaling there, but I guess it 
could be part of a two stage monitoring 
solution (you mention however a "declared 
peak bit rate" - sounds like signaling 
to me).

Section 5 is about system behaviour in the 
case of congestion. Would something like 
an "explicit congestion notification" of 
the backbone be useful? If end systems 
could, as a reaction on such a congestion 
indication, use codecs with lower bit rate 
for their MF-H traffic, additional calls 
may be accepted. 

Section 7.1: I'm not a queuing expert, but 
why would MF-M traffic see higher jitter? 
Aren't all MF packet in the same queue and 
those tagged as MF-M are discarded earlier? 
The result is higher loss probability, 
which is intended. But it shouldn't be 
higher jitter (don't earlier losses make 
it look like a "shorter" queue?).

Section 7.4 suggests the transmitter not to 
pause at the edge. ISPs may charge on volume 
and customers won't be happy if their 
terminal creates traffic while they aren't 
active. 
I understand the issue and I should offer 
an alternative. Some form of signaling based 
admission control in combination with 
measurements?

Section 7.5: The RMONMIB WG maintains some 
drafts promoting RAQMON. I'm not familiar with 
details, but your media monitoring server might 
require similar functionality. If you are 
interested:
http://www.ietf.org/internet-drafts/draft-ietf-rmonmib-raqmon-framework-02.txt

Regards, Rüdiger


Rüdiger Geib
T-Systems
Systems Integration
Senior Expert, Technologiezentrum
Am Kavalleriesand 3, 64295 Darmstadt
Germany
Fon: [phone]
http://www.t-systems.com
 

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