[SIPForum-discussion] What different between SIP and SIP-T protocol?

Mon Jul 14 01:18:12 UTC 2008

Hello Raghul,

Sorry for the slow response, outlook put this in the junk mail folder
for some reason!

First the Application media type is a catch all; it is used for discrete
data types which do not fit in any of the other categories (i.e. Image,
Audio or Video); the SDP indicates that the content of this block is
Session Description Protocol. This is as you said a normal arrangement
for SIP.

In SIP-T/I we need to carry SDP and ISUP so we put (in the messages with
both)

Multipart entities, this is where one or more different sets of data are
combined in a single body, (i.e. SDP and ISUP). Then the "mixed" subtype
follows, this is intended for use when the body arts are independent
(i.e. SDP and ISUP); then the boundary keyword ("=testing") tells us
where the data blocks split.

Then in the mixed case each block has a line which tells you what it is
(Content-Type: application/sdp) or (Content-Type: application/isup;
base=ansi88; version=ansi); notice that it tells us also the version of
ISUP, in this case ANSI (for North America) and it is the 1988 Version
of the C7/ISUP spec.

SIP (RFC 3261) used RFC2046 for the data blocks.

Best regards

Cliff Wignell

________________________________

From: Raghul Prasanna [mailto:raghul82 at yahoo.co.uk] 
Sent: Tuesday, 8 July 2008 8:19 AM
To: WIGNELL, CLIFFORD (CLIFFORD)
Subject: RE: [SIPForum-discussion] What different between SIP and SIP-T
protocol?

Hi Cliff,

 In your example I see the content type as
'multipart/mixed;boundary="testing'. Generally I have seen Content Type
as 'application/SDP', so does this content type means that it has ISUP
message encapsulated?

  Because this has both ISUP and SDP (from SIP) it states the content
type as multipart and mixed, is that so? Please explain.

Thanks,

Raghul

--- On Mon, 7/7/08, WIGNELL, CLIFFORD (CLIFFORD)
<cwignell at alcatel-lucent.com> wrote:

	From: WIGNELL, CLIFFORD (CLIFFORD) <cwignell at alcatel-lucent.com>
	Subject: RE: [SIPForum-discussion] What different between SIP
and SIP-T protocol?
	To: raghul82 at yahoo.co.uk
	Date: Monday, 7 July, 2008, 10:07 AM

	Hello Raghul

	Thank you

	Cliff Wignell

________________________________

	From: Raghul Prasanna [mailto:raghul82 at yahoo.co.uk] 
	Sent: Monday, 7 July 2008 6:01 PM
	To: Ho Lam; discussion at sipforum.org ; WIGNELL, CLIFFORD
(CLIFFORD)
	Subject: Re: [SIPForum-discussion] What different between SIP
and SIP-T protocol?

Excellent explanation Cliff..

Thanks,

Raghul

--- On Sun, 6/7/08, WIGNELL, CLIFFORD (CLIFFORD)
<cwignell at alcatel-lucent.com> wrote:

	From: WIGNELL, CLIFFORD (CLIFFORD) <cwignell at alcatel-lucent.com>
	Subject: [SIPForum-discussion] What different between SIP and
SIP-T protocol?
	To: "Ho Lam" <lamho at ftth.com.vn>, discussion at sipforum.org
	Date: Sunday, 6 July, 2008, 11:50 PM

	Hello all,

	There seems to be a lot of interest regarding SIP, SIP-I and
SIP-T, so I have resent one from a few weeks ago. (see below)

	Cliff Wignell

________________________________________________________________________
______________________________________________________________

	From: Ho Lam <lamho at ftth.com.vn>
	Subject: [SIPForum-discussion] What different between SIP and
SIP-T protocol?
	To: discussion at sipforum.org
	Date: Saturday, 5 July, 2008, 8:08 AM

	What different between SIP and SIP-T protocol?

	Ho Lam

________________________________________________________________________
______________________________________________________________

	Part 1, what are the differences between SIP, SIP-I and SIP-T.

	SIP-I and SIP-T are variants or extensions of SIP, which carry
PSTN/PLMN signalling (i.e. ISUP) information in the body of the
messages; SIP-I/T provides for:

	*         Interworking of ISUP parameters to SIP headers to
enable SIP based routing/features in the IP Core

	*         Encapsulation of ISUP using MIME header to enable
transparent ISUP through an IP core

	SIP-T/I specifies interworking between ISUP/BICC and SIP

	The interworking specifications include:

	*         Architectural context 

	*         Mappings for specific parameters

	*         Mechanism for encapsulating ISUP messages.

	SIP-T is specified in three IETF RFC's 3372, RFC 3398, RFC 3578

	SIP-I is the ITU specification for SIP interworking with
International ISUP   (Q.761-Q.764) and BICC (Q.1902.1-Q.1902.4) in
Q.1912.5 It specifies actions for three profiles, A, B, and C

	North American variations in ANSI T1.PP.679-2004

	SIP-I (Q.1912.5) and SIP-T are generally consistent; except for
subtle differences in terms of options, level of detail, and explicit
vs. implicit requirements

	SIP-I assumes a suitable "trust domain" exists between gateways

	SIP-T assumes it is always necessary to use cryptography verify
identity, establish trust, and to secure communication. 

	Q.1912.5 has been developed in the ITU-T and therefore has
benefited from extensive input from numerous carriers. 

	SIP-I is more robust relative to mapping ISUP messages and
parameters.

	SIP-T has been developed in IETF, and therefore has benefited
from a careful analysis of security considerations and provides more
detail in the context of public IP networks where "trust domains" may
not exist.

	The following is a SIP-T message, as you can see it is a typical
SIP INVITE with a MIME block added, in this case the ISUP is contained
with in the bock marked -testing and -testing-; the SIP call flow has
some implicates as there are a number of mid call ISUP messages which
may be present, if you look at the RFC's you will see examples of these.

	INVITE sip:3228880002 at 10.11.17.3 SIP/2.0

	Via: SIP/2.0/UDP 10.11.30.4:5070;branch=z9hG4bK63773d8-15942

	Max-Forwards: 70

	From: sip:4771110001 at 10.11.30.4:5070;tag=56077021

	To: <sip:4772220001 at 10.11.17.3;user=phone>

	Call-ID: 9234 at 10.11.30.4

	CSeq: 1 INVITE

	P-Asserted-Identity: Spectra2 <sip:4772220001 at 10.11.17.3:5070>

	Privacy: none

	Contact: <sip:4771110001 at 10.11.30.4:5070>

	Content-Type: multipart/mixed;boundary="testing"

	Content-Length: 299

	MIME-Version: 1.0

	--testing

	Content-Type: application/sdp

	v=0

	o=- 2890844526 2890844526 IN IP4 10.11.30.4

	s=-

	c=IN IP4 10.11.30.4

	t=0 0

	m=audio 6000 RTP/AVP 0

	a=rtpmap:0 PCMU/8000

	--testing

	Content-Type: application/isup; base=ansi88; version=ansi

	01 00 00 00 00 03 0f 16 0c d0 18 10 98 9e !,` c0 c6 e6 07 03 10
t'"00 10 

	07 03 10 t17 11 00 10 00 

	--testing-

	Part 2, where do you use SIP-I/T; any time you wish to transit
calls between PSTN/PLMN networks (over IP) where you want to retain the
ISUP information, some ISUP parameters affect the way calls are handled
and billed for so this is important in many cases. The second reason you
may want to use SIP-I/T is in the case you want to signal to the
PSTN/PLMN the need for a particular feature such as Call Completion to
Busy Subscriber (camp on), this requires ISUP signalling to go to the
terminating switch.

	I know that is a bit long but I hope it answers your question.

	Best regards

	Cliff Wignell

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