Subject: SIP and waste of bandwidth in wireless applications

From: Bruce Wiatrak <[email-masked]>
Date: Fri, 7 Aug 1998 12:31:49 -0500 (CDT)

Is seems to me that a Text Based call setup protocol
will waste bandwidth especially in wireless
applications where spectrum must be tightly
managed.

Also processing of Text strings requires more processing
than a bit oriented protocol.

In the SIP Draft dated July 16, 1998 section
1.5.3 it states that "it is believed that the additional
overhead of using a text-based protocol is not significant."

Call setup time in the wireless and landline telephony systems
is regarded as a required quality of service attribute.
Customers will not accept a much increased call setup time
because of the extra processing required to parse strings.

Are there plans to create a digital call setup protocol?

Bruce

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From: Jim Toga <[email-masked]>
Date: Fri, 07 Aug 1998 11:00:56 -0700

The ITU-T has one defined : H.323.

>Are there plans to create a digital call setup protocol?

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From: Christian Huitema <[email-masked]>
Date: Fri, 7 Aug 1998 14:04:03 -0400 (EDT)

On Aug 7, 12:31pm, Bruce Wiatrak wrote:
> Subject: SIP and waste of bandwidth in wireless applications
> 

Text encodings are typically 20% to 100% larger than binary encodings.
This is indeed significant.  However, the impact is less than you
think in an Internet environment where payload packets and signalling
packets share the same channels.  A connection set-up requires 6 or
7 messages, while the voice channel alone requires about 20 messages
per second if you want to maintain reasonably interactive delays.

> than a bit oriented protocol.

The difference is marginal -- it mostly depend on the optimisation level
of your code.

In traditional Ip networks, the ease of debugging + ease of monitoring,
testing, etc, more than compensates the overhead.  I suspect that the
same would hold true in reasonable wireless configurations.

-- 
Christian Huitema

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From: Jon Crowcroft <[email-masked]>
Date: Fri, 07 Aug 1998 19:05:45 +0200

>>applications where spectrum must be tightly
 
hunh -if you have enough for speech (e.g. 3kbps) why are you worried
about a 2 packet exchange of relatively short packets - itsnot
bandwidth - you _might_ just argue it will increase rhe latency

 >>than a bit oriented protocol.
not on any reasoanble processor i knwo of - any s/w implementaiton
will be way better on byte rtaher than bit - evcen intel CISC *86
processors are, and any risc (e.g. amd29000, mips, ARM, sparc, blah
blah) will have much less hassle with string matching than bit
twiddling.....

same arugment dicated the dssign of byte oriented framing protocols
for data comms ratehr than hdlc bit oreiented stuffing which is a
terrible headache....

ditto H221 framing/muxing versus RTP...

 >>because of the extra processing required to parse strings.
 
this is true - the latecny could be argued (though it wont realy be
significant) - i dont buy the processing overhead argument 1 bit

thats my 2 cents:-)

 >>Are there plans to create a digital call setup protocol?
 
um - well, what are your goals? what s/w (or h/w) do expect to design
in an IP mobile phone? if its a GSM phone with a PDA function, then
it'll have an ARM or sometyhing similar....

 cheers

   jon

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From: Bruce Wiatrak <[email-masked]>
Date: Fri, 7 Aug 1998 13:13:01 -0500 (CDT)

H.323 refers to H.225 which is a subset of the
of the Q.931 standard. Q.931 is the ISDN
call setup protocol.

It seems the SIP and
H.225 (H.323) are competing standards for call setup (control)
in internet telephony

If IETF is pushing a text based call setup protocol
and it becomes the defacto standard for internet telephony
the text based protocol will not lend itself well to
the wireless applications.
The control channel in cellular systems will become clogged with
text messages for call setup.

Bruce

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From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 07 Aug 1998 15:28:47 -0400

Christian Huitema wrote:
> This is indeed significant.

I'd really be interested to know about comparisons with something like
ASN.1. There are overheads associated with both PER and BER as well, so
it would be nice to get a real number instead of everyone just guessing.

The size will also depend on the amount of data sent. A binary based
protocol with a lot more mandatory elements could in the end be larger
than a textual protocol with fewer.

 However, the impact is less than you
> per second if you want to maintain reasonably interactive delays.

A SIP exchange is three in general; unless maybe you are counting things
like DNS and ARP? Actually, packet rates are likely around 30 per second
(using G.723.1 = 30ms frames and 1 frame per packet = 33 packets per
second).

> The difference is marginal -- it mostly depend on the optimisation level

You'll spend *way* more time doing any reasonable speech compression
than parsing the text of the message.

-Jonathan R.

-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
FAX:   (732) 834-5379                       Rm. 4C-526
EMAIL: [email-masked]
URL: http://www.cs.columbia.edu/~jdrosen

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From: "Henry Sinnreich" <[email-masked]>
Date: Fri, 7 Aug 1998 14:46:37 -0500

> text messages for call setup.

Please see Christian's and Jon's notes. I would like to add that wireless IP
devices may not necessarily be architected with the control channel that you
mention. The wireless IP services also deploy larger bandwidth. So the size
of text based control messages matters even less.

Henry

Henry Sinnreich
MCI, 901 International Parkway
Richardson, Texas 75082

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On Behalf Of
> Bruce Wiatrak
> Sent: Friday, August 07, 1998 1:13 PM
> To: Jim Toga; Bruce Wiatrak; [email-masked]
> Subject: Re: SIP and waste of bandwidth in wireless applications
>
>
>

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From: Jon Crowcroft <[email-masked]>
Date: Sat, 08 Aug 1998 23:29:20 +0200

In message <[email-masked]>, Jonathan Rosenberg typed:

see craig partridge's work (off henning's excellent bibliographic
search site) on different data ,representations

the space/CPU trade offs are not brilliantly in favour of ASN.1/BER or
PER....imho

buton a continuous media channel, forget it..

and in detail, H.x and S.x protocols are pretty similar jn message
size, so then its just CPU, where the string encodijng wil win way
better that tagged or embedded bit coded application level protocols

and everytin else you say is also true!
 >>Christiaa Huitema wrote:

 cheers

   jon