Subject: RE: [NSIS] layer split summary? opinions?

From: [email-masked]
Date: Tue, 4 Feb 2003 16:30:56 +0200

Hi,

> >  The goal of NSIS WG is to make a lightweight signaling (xRSVP), 
> >  so there are a lot of overhead if xRSVP using TCP is used 
> in mobile (access) envrionments.
> > 
> 
> I'm guessing that your mobile device has a web browser (HTTP), an email 
> client (POP, IMAP, SMTP) and maybe even a SIP UA. How many queries a 
> second does your web browser do? Compared to a signaling protocol?
> 
> Which do you think will do better in your mobile environment: your 
> already-tuned-for-mobility TCP stack that you need for HTTP, IMAP, SMTP 
> and possibly SIP or RTSP or a let's-develop-a-new-transport protocol 
> that we'll develop for this special purpose?

Just playing the devil's advocate, the problem with TCP on mobile phones
isn't the stack, the resource usage or power - it is about the latency.
GPRS and CDMAx1 both have very high RTTs.  If a new TCP connection needs
to be opened, then this will put a significant delay.  However, this 
would be mitigated by multiplexing over a single TCP connection.  In
practice, we should see (in NSIS) how this could be done for a signaling
protocol.

br,
John
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From: "Lars.Westberg" <[email-masked]>
Date: Mon, 10 Feb 2003 09:14:19 +0100

Comment to the RTT:
One problem with TCP/SCTP over air-interace is the response time to establish
a session e.g. the time to get the reservation done over the air-interface
and the infrastructure.
This is not only due to long RTT  but also that the radio-channel has a very
low-bitrate. The combination of low-bitrate channel, RTT  and tight response
time requirements may be difficult to fulfill with TCP.
The response time problems have ben previously discussed in the ROCH working
group
for large SIP-payloads.

I think that we have to allow different transport protocol and I propose a
lightweigth RSVP  as one of the solution.

- Lasse