Ejemplos SIP RFC 3261

http://www.tech-invite.com
RFC 3261's SIP Examples
V2.4 – January 2, 2008

biloxi.com Bob's
Registrar SIP phone

.REGISTER. This is a representation, as a slide
show, of the SIP examples outlined in
.200 OK. chapter 4 (overview of operation) and
detailed in chapter 24 of RFC 3261 –
Alice's atlanta.com biloxi.com SIP: Session Initiation Protocol.
softphone Proxy Proxy
SIP messages are reported in strict
.INVITE. conformance with this RFC.
Copyright © 2005-2008 Tech-invite.com Joël Repiquet. All Rights Reserved.

.100 Trying.
.INVITE.
.100 Trying.
.INVITE.

.180 Ringing.

.180 Ringing.

.180 Ringing.
.200 OK.

.200 OK.

.200 OK.

.ACK.

..Media Session..

.BYE.

.200 OK.

17 pages

RFC 3261's Example – Registration (a)

Location
Server

The Request-URI
atlanta.com biloxi.com names the domain
of the location
proxy proxy
service for which
the registration is
meant

biloxi.com
registrar
The To header field contains the address of record
whose registration is to be created

F1
The From header field contains the address-of-record REGISTER sip:registrar.biloxi.com SIP/2.0
of the person responsible for the registration. The Via: SIP/2.0/UDP bobspc.biloxi.com:5060
value is the same as the To header field unless the ;branch=z9hG4bKnashds7
request is a third-party registration.
Max-Forwards: 70
To: Bob <sip:bob@biloxi.com>
From: Bob <sip:bob@biloxi.com>
All registrations from a UA should use the ;tag=456248
same Call-ID header field value for Call-ID: 843817637684230@998sdasdh09
registrations sent to a particular registrar.
CSeq: 1826 REGISTER
Contact: <sip:bob@192.0.2.4>
Expires: 7200
The CSeq value guarantees proper ordering Content-Length: 0
of REGISTER requests. A UA must increment
the CSeq value by one for each REGISTER
request with the same Call-ID.

The Expires header field indicates
how long the UA would like the
The Contact header field with zero or more binding to be valid. The value is a
values containing address bindings. number indicating seconds. Bob's
Alice's
SIP
softphone
phone

RFC 3261's Example – Registration (b)

Location
Server

Store
atlanta.com biloxi.com
proxy proxy

biloxi.com
registrar

F2
SIP/2.0 200 OK
Via: SIP/2.0/UDP bobspc.biloxi.com:5060
;branch=z9hG4bKnashds7
;received=192.0.2.4
;tag=2493k59kd
;tag=456248
Call-ID: 843817637684230@998sdasdh09
CSeq: 1826 REGISTER
Expires: 7200
Content-Length: 0

Bob's
Alice's
SIP
softphone
phone

RFC 3261's Example – Session Setup (1)

The Via header field indicates the transport (UDP)
used for the transaction and identifies the location
-- sent-by (pc33.atlanta.com) -- where the
The initial Request-URI response is to be sent. The quot;branchquot; parameter is
of the message is set used to identify the transaction created by that
to the value of the URI request. It is mandatory and must always begin
in the To field. with the characters quot;z9hG4bKquot;.

atlanta.com The Max-Forwards header field serves to limit biloxi.com
proxy the number of hops a request can transit on the proxy
way to its destination. It is decremented by one
at each hop.

The To header field specifies the desired quot;logicalquot; recipient of the request, or
the address-of-record (AOR) of the user or resource that is the target of this
F1 request. There is no quot;tagquot; parameter since the dialog is not established yet.
INVITE sip:bob@biloxi.com SIP/2.0

Via: SIP/2.0/UDP pc33.atlanta.com
;branch=z9hG4bKnashds8 The From header field indicates the logical identity of the initiator of the
Max-Forwards: 70 request, possibly the user's address-of-record. quot;Alicequot; is the (optional)
To: Bob <sip:bob@biloxi.com> display name. The quot;tagquot; parameter identifies this UA as a peer of the dialog.
From: Alice <sip:alice@atlanta.com>
;tag=1928301774
Call-ID: a84b4c76e66710 The Call-ID header field acts as a unique identifier and must be the same
CSeq: 314159 INVITE for all requests and responses sent by either UA in a dialog.
Contact: <sip:alice@pc33.atlanta.com>
Content-Type: application/sdp
The CSeq header field serves as a way to identify and order transactions. It
Content-Length: 142 consists of a sequence number and a method, matching that of the request.

(Alice's SDP not shown)
The Contact header field provides a SIP or SIPS URI that can be used by
Bob's UA to contact Alice's UA for subsequent requests.

The Content-Type header field indicates the media type of the message-body sent
to the recipient. SDP (session description protocol ) is defined in RFC 4566.

Alice's user agent (UA) does not know the location of Bob's UA or his Bob's
Alice's server in the biloxi.com domain. Therefore, the INVITE request is sent to SIP
softphone the SIP server that serves Alice's domain (atlanta.com). The address of
phone
the atlanta.com SIP server could have been configured in Alice's
softphone, or it could have been discovered by DHCP, for example.

The quot;atlanta.comquot; proxy server finds the SIP proxy server that serves the
quot;biloxi.comquot; domain by performing a particular type of DNS lookup. This
procedure (selecting a transport protocol, determining port and IP
address) is described in RFC 3263 (SIP: Locating SIP Servers). Before forwarding the INVITE request, the quot;atlanta.comquot;
server adds an additional Via header field value that contains
its own address -- sent-by (bigbox3.site3.atlanta.com) -- and
the quot;branchquot; transaction value

F3
INVITE sip:bob@biloxi.com SIP/2.0
atlanta.com Via: SIP/2.0/UDP bigbox3.site3.atlanta.com biloxi.com
proxy ;branch=z9hG4bK77ef4c2312983.1 proxy
;received=192.0.2.1
Max-Forwards: 69
F2 To: Bob <sip:bob@biloxi.com>
The quot;receivedquot; parameter is added to
SIP/2.0 100 Trying the Via header field built by Alice's
;tag=1928301774
Via: SIP/2.0/UDP pc33.atlanta.com UA (as for quot;100 Tryingquot; message).

Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
;received=192.0.2.1
Contact: <sip:alice@pc33.atlanta.com>
Content-Type: application/sdp Max-Forwards is decremented by one
Content-Length: 142
;tag=1928301774
CSeq: 314159 INVITE
The remainder of the INVITE request
Content-Length: 0
received from Alice's UA is unchanged.

The 100 (Trying) response contains the same To, From, Call-ID, CSeq
header field values as the INVITE request.

The quot;receivedquot; parameter is added to the Via header field by the quot;server
transportquot; of atlanta.com proxy, after examining the value of the sent-by
parameter (pc33.atlanta.com). This sent-by parameter was inserted by
the UA's quot;client transportquot; in the Via header field value, just before
sending the INVITE request. The sent-by field contained an IP address or
host name, and port. The quot;receivedquot; parameter contains the IP source
address from which the packet was received. Bob's
Alice's
SIP
softphone
phone


The proxy server consults
the location server database,
Location Response
that contains the current IP
Server Query address of Bob.

F4
SIP/2.0 100 Trying
;received=192.0.2.2
;received=192.0.2.1
F5
From: Alice <sip:alice@atlanta.com> INVITE sip:bob@192.0.2.4 SIP/2.0
;tag=1928301774 Via: SIP/2.0/UDP server10.biloxi.com

Call-ID: a84b4c76e66710 ;branch=z9hG4bK4b43c2ff8.1
CSeq: 314159 INVITE Via: SIP/2.0/UDP bigbox3.site3.atlanta.com
Content-Length: 0 ;branch=z9hG4bK77ef4c2312983.1
;received=192.0.2.2
Before forwarding the INVITE request, the
;received=192.0.2.1
quot;biloxi.comquot; server adds an additional Via
Max-Forwards: 68
header field value that contains its own address
;tag=1928301774
The quot;receivedquot; parameter is added to the Via header CSeq: 314159 INVITE
field built by quot;atlanta.comquot; proxy server Contact: <sip:alice@pc33.atlanta.com>
Content-Length: 142

Max-Forwards is decremented by one

Bob's
Alice's The remainder of the INVITE request SIP
softphone received from quot;atlanta.comquot; proxy
phone
server is unchanged.


proxy proxy

The quot;receivedquot; parameter is added to the Via F6
header field built by quot;biloxi.comquot; proxy server
SIP/2.0 180 Ringing

Via: SIP/2.0/UDP server10.biloxi.com
;branch=z9hG4bK4b43c2ff8.1
The quot;tagquot; parameter, identifying this UA as a ;received=192.0.2.3
peer of the dialog, is added to the To header Via: SIP/2.0/UDP bigbox3.site3.atlanta.com
field. Although the dialog is not established yet, ;branch=z9hG4bK77ef4c2312983.1
the 3 values that identify a dialog (Call-ID, local ;received=192.0.2.2
Tag, remote Tag) are already defined. Via: SIP/2.0/UDP pc33.atlanta.com
;received=192.0.2.1
The Contact header field provides a SIP or SIPS To: Bob <sip:bob@biloxi.com>
URI that can be used by Alice's UA to contact ;tag=a6c85cf
Bob's UA for subsequent requests. From: Alice <sip:alice@atlanta.com>
;tag=1928301774
CSeq: 314159 INVITE
The other header field values (From, Call-ID, Content-Length: 0
CSeq, and bottom Via's) are copied from the
INVITE request.

Bob's SIP phone rings and indicates this in a 180 Bob's
Alice's (Ringing) response, which is routed back in the
SIP
softphone reverse direction to biloxi.com proxy (IP address
and transport found in the top Via header field) phone


F7
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP bigbox3.site3.atlanta.com
;branch=z9hG4bK77ef4c2312983.1
proxy ;received=192.0.2.2
proxy
;received=192.0.2.1
;tag=a6c85cf
From: Alice <sip:alice@atlanta.com> The top Via header field in the 180
;tag=1928301774 (Ringing) message received from

Call-ID: a84b4c76e66710 Bob's UA, is used by biloxi.com
Contact: <sip:bob@192.0.2.4> proxy server for retrieving the
CSeq: 314159 INVITE relevant transaction, using the
quot;branchquot; parameter. It is then
Content-Length: 0
removed and the information in
the new top Via header field is
used for forwarding the message
towards the next hop in the
reverse path: atlanta.com proxy.

Bob's
Alice's
SIP
softphone
phone


proxy proxy

F8

SIP/2.0 180 Ringing
;received=192.0.2.1
;tag=a6c85cf
The top Via header field in the 180
(Ringing) message received from
;tag=1928301774 biloxi.com proxy, is used by atlanta.com
Call-ID: a84b4c76e66710 proxy server for retrieving the relevant
Contact: <sip:bob@192.0.2.4> transaction, using the quot;branchquot;
CSeq: 314159 INVITE parameter. It is then removed and the
Content-Length: 0 information in the new top Via header
field is used for forwarding the message
towards the next hop in the reverse
path: Alice's UA.

Alice's softphone passes the Ringing information to Bob's
Alice's
Alice, using an audio ringback tone or by displaying SIP
softphone a message on Alice's screen. phone


quot;CSeq: 314159 INVITEquot; / quot;branch=z9hG4bK4b43c2ff8.1quot;
transaction, between biloxi.com proxy and Bob's UA,
terminates with this 200 (OK) response

proxy proxy

F9
SIP/2.0 200 OK
Via: SIP/2.0/UDP server10.biloxi.com

;branch=z9hG4bK4b43c2ff8.1
;received=192.0.2.3
Via: SIP/2.0/UDP bigbox3.site3.atlanta.com
;branch=z9hG4bK77ef4c2312983.1
;received=192.0.2.2
;received=192.0.2.1
;tag=a6c85cf
;tag=1928301774
CSeq: 314159 INVITE
Content-Length: 131

(Bob's SDP not shown)

When Bob answers the call, his SIP phone sends a Bob's
Alice's 200 (OK) response to indicate that the call has been SIP
softphone answered. The 200 (OK) contains a message body
phone
with the SDP media description of the type of session
that Bob is willing to establish with Alice.


quot;CSeq: 314159 INVITEquot; / quot;branch=z9hG4bK77ef4c2312983.1quot;
transaction, between biloxi.com proxy and atlanta.com proxy,

F10
SIP/2.0 200 OK
;received=192.0.2.2
;received=192.0.2.1
;tag=a6c85cf

;tag=1928301774
CSeq: 314159 INVITE
Content-Length: 131


Bob's
Alice's
SIP
softphone
phone


proxy proxy

F11

SIP/2.0 200 OK
;received=192.0.2.1
;tag=a6c85cf
;tag=1928301774
CSeq: 314159 INVITE
Content-Length: 131


quot;CSeq: 314159 INVITEquot; / quot;branch=z9hG4bKnashds8quot;
transaction, between atlanta.com proxy and Alice's UA,

Bob's
Alice's Alice's softphone stops the ringback tone and
SIP
softphone indicates that the call has been answered
phone


proxy proxy

Alice's softphone sends an ACK (message
request) to Bob's SIP phone to confirm the
reception of the final response (200 (OK)).
In this example, the ACK is sent directly from
Alice's softphone to Bob's SIP phone,
bypassing the two proxies. This occurs
because the endpoints have learned each
other's address from the Contact header F12
fields through the INVITE/200 (OK) ACK sip:bob@192.0.2.4 SIP/2.0
exchange, which was not known when the Via: SIP/2.0/UDP pc33.atlanta.com
initial INVITE was sent.
Max-Forwards: 70
;tag=a6c85cf
;tag=1928301774 Bob's
Alice's
Call-ID: a84b4c76e66710 SIP
softphone
CSeq: 314159 ACK phone
Content-Length: 0


proxy proxy

Alice and Bob's media session has now begun, and
they send media packets using the format to
which they agreed in the exchange of SDP. In
general, the end-to-end media packets take a
different path from the SIP signaling messages.

One or a combination of the following media types
can be used with SDP: quot;audioquot;, quot;videoquot;,
quot;applicationquot;, quot;dataquot;, quot;controlquot;...

Bob's
Alice's
softphone
Media Session SIP
phone


proxy proxy

At the end of the call, Bob disconnects
F13 (hangs up) first and his SIP phone
BYE sip:alice@pc33.atlanta.com SIP/2.0 generates a BYE (request) message.
Via: SIP/2.0/UDP 192.0.2.4 This BYE is routed directly to Alice's
;branch=z9hG4bKnashds10 softphone, again bypassing the proxies.
Max-Forwards: 70
;tag=a6c85cf
To: Alice <sip:alice@atlanta.com>
;tag=1928301774 Bob's
Alice's
Call-ID: a84b4c76e66710 SIP
softphone
CSeq: 231 BYE phone
Content-Length: 0


proxy proxy

F14
Alice confirms receipt of the BYE with a SIP/2.0 200 OK
200 (OK) response, which terminates
Via: SIP/2.0/UDP 192.0.2.4
the session and the BYE transaction.
;tag=a6c85cf
To: Alice <sip:alice@atlanta.com>
;tag=1928301774
Call-ID: a84b4c76e66710 Bob's
Alice's
CSeq: 231 BYE SIP
softphone
Content-Length: 0 phone

RFC 3261's Example – Session Setup (end)

proxy proxy

Bob's
Alice's
SIP
softphone
phone

Ejemplos SIP RFC 3261

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Ejemplos SIP RFC 3261