Subject: [Simple] MSRP Comments

From: Cullen Jennings <[email-masked]>
Date: Sun, 09 Nov 2003 21:16:14 -0800

The draft does not say much about if the forming a separate TCP connection
for each session between two relays. Some people have said this will use
less bandwidth than a single connection. I think it will consume much more.
The question is if this is trashing the commons or not -  I don't know.
Given one of the major reasons for not just using Page mode for everything
revolves around concession control, I think it needs a little discussion.
Not that we are doing this but ... Setting up a new TCP connection for every
UDP packet you want to send completely defeats the congestion control
properties of TCP.

I would prefer if it said you MUST implement both passive and active. I
think it is unacceptable that two clients could be fully compliant with the
RFC and not be able to send message to each other. I'm fine with them be
configured such that they can't.

I don't see the need to support switching to TLS after the first message has
been received. This just introduces to many weird things to figure out on
authorization. Why would you switch?

TLS is way underspecified - what do the certs need to say - how does mutual
TLS work - can two relays use self signed certs  - how would that work. I
know I have threatened to send text before - hopefully I will at some point
:-)

It's not really clear how you switch to a TLS session. I'm very suspicious
that the look ahead scheme to switch to TLS is going to be very hard to
integrate with existing libraries -  I'm fairly confident that STARTLS will
work so why not use it?

I still think the draft should explicitly discuss more than two relays.
There are many needs to relays and saying put a full B2BUA in to meet all
these other needs is bogus. I expect this comment to be ignored :-)

I like the resolution of new sessions for large messages or separate
conversation threads.

Cullen

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From: Ben Campbell <[email-masked]>
Date: Mon, 10 Nov 2003 10:01:13 -0600

Cullen Jennings wrote:

> for each session between two relays. 

I suspect there is a typo in this sentence: Is the "if" spurious, or is 
something else missing? (Really, I am not trying to pick at typos--I am 
just not sure of the meaning.)

>Some people have said this will use

I was not aware anyone thought using a connection per session would 
require less bandwidth than shared connections. The arguments against 
shared sessions were based on protocol complexity and head-of-line 
blocking issues.

> UDP packet you want to send completely defeats the congestion control

Do you mean more discussion in the document, or in the work group? We 
have discussed this a lot in the group, and I have not heard a new 
argument in a while now...

> configured such that they can't.

Agreed.

> authorization. Why would you switch?

I personally agree with your position, but the consensus in Vienna 
seemed to be to allow switching in mid-stream. It is of course possible 
that I misunderstood this, and will be _very_ happy to change it if that 
is the case.

> know I have threatened to send text before - hopefully I will at some point

I share your hope in this matter ;-)

> these other needs is bogus. I expect this comment to be ignored :-)

Noted :-)

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From: Ben Campbell <[email-masked]>
Date: Mon, 10 Nov 2003 10:01:13 -0600

Agreed.

Noted :-)

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From: Cullen Jennings <[email-masked]>
Date: Mon, 10 Nov 2003 12:19:33 -0800

Inline ... I have tried to explain this better at the bottom ...

> just not sure of the meaning.)

Very sorry - yes, I did not mean to put the "if"
 
> shared sessions were based on protocol complexity and head-of-line

I phrased this very poorly - I was not actually worried about the issue
where slightly more bits are transported when using two streams than one. My
concern was around the congestion control properties of N parallel TCP
streams VS 1. Particularly what percentage of the total available bandwidth
this 1 or N streams will get, and what percentage it deservers.

> argument in a while now...

The last email I seem to have on it has Dean presenting a reasonable
argument that the effect will be X and Jonathan presenting a reasonable
argument the the effect will be not X. See

www1.ietf.org/mail-archive/working-groups/simple/current/msg01316.html

I don't think this ever got resolved.

Let's go with the following assumptions which may or may not be relevant.
There are two relays that have 100k sessions between them. Each session
sends an 1k IM message every 10 seconds. The link is horribly congested and
has a 10% packet loss. Imagine there is also a bunch of SMTP traffic over
the same link. 

What will happen in both the 1 stream and 100k stream case? How does the
relative percentage of IM to SMTP compare in both cases? How does the 100k
stream case compare to if the packets had been sent over UDP?

Cullen

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From: Cullen Jennings <[email-masked]>
Date: Mon, 10 Nov 2003 12:19:33 -0800

Cullen