SIPPING Working Group A. Johnston
Internet Draft WorldCom
Document: S. Donovan
draft-ietf-sipping-basic-call-flows-01.txt R. Sparks
Expires: April 2003 C. Cunningham
dynamicsoft
K. Summers
Sonus
October 2002
Session Initiation Protocol Basic Call Flow Examples
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This informational document gives examples of Session Initiation
Protocol (SIP) call flows. Elements in these call flows include SIP
User Agents and Clients, SIP Proxy and Redirect Servers. Scenarios
include SIP Registration and SIP session establishment. Call flow
diagrams and message details are shown.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
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SIP Basic Call Flow Examples October 2002
Table of Contents
1. Overview.......................................................2
1.1 General Assumptions........................................3
1.2 Legend for Message Flows...................................3
1.3 SIP Protocol Assumptions...................................3
2. SIP Registration...............................................5
2.1 Successful New Registration................................5
2.2 Update of Contact List.....................................7
2.3 Request for Current Contact List...........................9
2.4 Cancellation of Registration..............................11
2.5 Unsuccessful Registration.................................13
3. SIP Session Establishment.....................................15
3.1 Successful Session Establishment..........................15
3.2 Session Establishment Through Two Proxies.................18
3.3 Session with Multiple Proxy Authentication................28
3.4 Successful Session with Proxy Failure.....................38
3.5 Session Through a SIP ALG.................................47
3.6 Session via Redirect and Proxy Servers with SDP in ACK....55
3.7 Session with re-INVITE (IP Address Change)................62
3.8 Unsuccessful No Answer....................................68
3.9 Unsuccessful Busy.........................................76
3.10 Unsuccessful No Response from User Agent.................81
3.11 Unsuccessful Temporarily Unavailable.....................86
Security Considerations..........................................91
References.......................................................91
Acknowledgments..................................................92
Author's Addresses...............................................92
1. Overview
The call flows shown in this document were developed in the design of
a SIP IP communications network. They represent an example
minimum set of functionality.
It is the hope of the authors that this document will be useful for
SIP implementors, designers, and protocol researchers alike and will
help further the goal of a standard implementation of RFC 3261[2].
These flows represent carefully checked and working group reviewed
scenarios of the most basic examples as a companion to the
specifications.
These call flows are based on the current version 2.0 of SIP in
RFC 3261[2] with SDP usage described in RFC 3264[3]. Other RFCs also
comprise the SIP standard but are not used in this set of basic call
flows.
Call flow examples of SIP interworking with the PSTN through gateways
are contained in a companion document, RFC xxxx[4].
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SIP Basic Call Flow Examples October 2002
1.1 General Assumptions
A number of architecture, network, and protocol assumptions underlie
the call flows in this document. Note that these assumptions are not
requirements. They are outlined in this section so that they may be
taken into consideration and to aid in the understanding of the call
flow examples.
The authentication of SIP User Agents in these example call flows is
performed using HTTP Digest as defined in [2] and [5].
Some Proxy Servers in these call flows insert Record-Route headers
into requests to ensure that they are in the signaling path for
future message exchanges.
These flows show TCP, TLS, and UDP for transport. Other transport
schemes could also be used. If UDP is used, care must be taken to
avoid packet fragmentation and congestion.
1.2 Legend for Message Flows
Dashed lines (---) represent signaling messages that are mandatory to
the call scenario. These messages can be SIP or PSTN
signaling. The arrow indicates the direction of message flow.
Double dashed lines (===) represent media paths between network
elements.
Messages with parentheses around their name represent optional
messages.
Messages are identified in the Figures as F1, F2, etc. This
references the message details in the list that follows the Figure.
Comments in the message details are shown in the following form:
/* Comments. */
1.3 SIP Protocol Assumptions
This document is informational only and is NOT NORMATIVE in any
sense, in that it does not prescribe the flows that are shown, indeed
they MUST NOT be copied due to the reasons described in the next
paragraph. On the other hand, the basic call flows represent well-
reviewed examples of SIP usage that are best common practice
according to community consensus.
For simplicity in reading and editing the document, there are a
number of differences between some of the examples and actual SIP
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SIP Basic Call Flow Examples October 2002
messages. For example, the HTTP Digest responses are not actual MD5
encodings. Call-IDs are often repeated, and CSeq counts often begin
at 1. Header fields are usually shown in the same order. Usually
only the minimum required header field set is shown, others that
would normally be present such as Accept, Supported, Allow, etc are
not shown.
Actors:
Element Display Name URI IP Address
------- ------------ --- ----------
User Agent BigGuy UserA@atlanta.com 192.0.2.101
User Agent LittleGuy UserB@biloxi.com 192.0.2.201
User Agent UserB@chicago.com 192.0.2.100
Proxy Server ss1.atlanta.com 192.0.2.111
Proxy/Registrar ss2.biloxi.com 192.0.2.222
Proxy Server ss3.chicago.com 192.0.2.233
ALG alg1.atlanta.com 192.0.2.128
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SIP Basic Call Flow Examples October 2002
2. SIP Registration
Registration binds a particular device Contact URI with a SIP user
Address of Record (AOR).
2.1 Successful New Registration
User B SIP Server
| |
| REGISTER F1 |
|------------------------------>|
| 401 Unauthorized F2 |
|<------------------------------|
| REGISTER F3 |
|------------------------------>|
| 200 OK F4 |
|<------------------------------|
| |
User B sends a SIP REGISTER request to the SIP server. The request
includes the user's contact list. This flow shows the use of HTTP
Digest for authentication using TLS transport. TLS transport is used
due to the lack of integrity protection in HTTP Digest and the danger
of registration hijacking without it, as described in RFC 3261 [2].
The SIP server provides a challenge to User B. User B enters her/his
valid user ID and password. User B's SIP client encrypts the user
information according to the challenge issued by the SIP server and
sends the response to the SIP server. The SIP server validates the
user's credentials. It registers the user in its contact database
and returns a response (200 OK) to User B's SIP client. The response
includes the user's current contact list in Contact headers. The
format of the authentication shown is HTTP digest. It is assumed
that User B has not previously registered with this Server.
Message Details
F1 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Contact: <sip:UserB@client.biloxi.com>
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Content-Length: 0
F2 401 Unauthorized SIP Server -> User B
SIP/2.0 401 Unauthorized
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>;tag=1410948204
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
WWW-Authenticate: Digest realm="atlanta.com", qop="auth",
nonce="ea9c8e88df84f1cec4341ae6cbe5a359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F3 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=ja743ks76zlflH
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 2 REGISTER
Contact: <sip:UserB@client.biloxi.com>
Authorization: Digest username="UserB", realm="atlanta.com"
nonce="ea9c8e88df84f1cec4341ae6cbe5a359", opaque="",
uri="sip:ss2.biloxi.com", response="dfe56131d1958046689d83306477ecc"
Content-Length: 0
F4 200 OK SIP Server -> B
SIP/2.0 200 OK
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=ja743ks76zlflH
To: LittleGuy <sip:UserB@biloxi.com>;tag=37GkEhwl6
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 2 REGISTER
Contact: <sip:UserB@client.biloxi.com>;expires=3600
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
2.2 Update of Contact List
User B SIP Server
| |
| REGISTER F1 |
|------------------------------>|
| 200 OK F2 |
|<------------------------------|
| |
User B wishes to update the list of addresses where the SIP server
will redirect or forward INVITE requests.
User B sends a SIP REGISTER request to the SIP server. User B's
request includes an updated contact list. Since the user already has
authenticated with the server, the user supplies authentication
credentials with the request and is not challenged by the server.
The SIP server validates the user's credentials. It registers the
user in its contact database, updates the user's contact list, and
returns a response (200 OK) to User B's SIP client. The response
includes the user's current contact list in Contact headers.
Message Details
F1 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Contact: mailto:UserB@biloxi.com
Authorization: Digest username="UserB", realm="atlanta.com",
qop="auth", nonce="1cec4341ae6cbe5a359ea9c8e88df84f", opaque="",
uri="sip:ss2.biloxi.com",
response="71ba27c64bd01de719686aa4590d5824"
Content-Length: 0
F2 200 OK SIP Server -> B
SIP/2.0 200 OK
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
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SIP Basic Call Flow Examples October 2002
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>;tag=34095828jh
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Contact: <sip:UserB@client.biloxi.com>;expires=3600
Contact: <mailto:UserB@biloxi.com>;expires=4294967295
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
2.3 Request for Current Contact List
User B SIP Server
| |
| REGISTER F1 |
|------------------------------>|
| 200 OK F2 |
|<------------------------------|
| |
User B sends a register request to the Proxy Server containing no
Contact headers, indicating the user wishes to query the server for
the user's current contact list. Since the user already has
authenticated with the server, the user supplies authentication
credentials with the request and is not challenged by the server. The
SIP server validates the user's credentials. The server returns a
response (200 OK) which includes the user's current registration list
in Contact headers.
Message Details
F1 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Authorization: Digest username="UserB", realm="atlanta.com",
nonce="df84f1cec4341ae6cbe5ap359a9c8e88", opaque="",
uri="sip:ss2.biloxi.com",
response="aa7ab4678258377c6f7d4be6087e2f60"
Content-Length: 0
F2 200 OK SIP Server -> B
SIP/2.0 200 OK
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>;tag=jqoiweu75
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
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SIP Basic Call Flow Examples October 2002
Contact: <sip:UserB@client.biloxi.com>;expires=3600
Contact: <mailto:UserB@biloxi.com>;expires=4294967295
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
2.4 Cancellation of Registration
User B SIP Server
| |
| REGISTER F1 |
|------------------------------>|
| 200 OK F2 |
|<------------------------------|
| |
User B wishes to cancel their registration with the SIP
server. User B sends a SIP REGISTER request to the
SIP server. The request has an expiration period of 0 and applies to
all existing contact locations. Since the user already has
authenticated with the server, the user supplies authentication
credentials with the request and is not challenged by the server.
The SIP server validates the user's credentials. It clears the
user's contact list, and returns a response (200 OK) to User B's SIP
client.
Message Details
F1 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Expires: 0
Contact: *
Authorization: Digest username="UserB", realm="atlanta.com",
nonce="88df84f1cac4341aea9c8ee6cbe5a359", opaque="",
uri="sip:ss2.biloxi.com",
response="ff0437c51696f9a76244f0cf1dbabbea"
Content-Length: 0
F2 200 OK SIP Server -> B
SIP/2.0 200 OK
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>;tag=1418nmdsrf
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SIP Basic Call Flow Examples October 2002
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
2.5 Unsuccessful Registration
User B SIP Server
| |
| REGISTER F1 |
|------------------------------>|
| 401 Unauthorized F2 |
|<------------------------------|
| REGISTER F3 |
|------------------------------>|
| 401 Unauthorized F4 |
|<------------------------------|
| |
User B sends a SIP REGISTER request to the SIP Server. The SIP
server provides a challenge to User B. User B enters her/his user ID
and password. User B's SIP client encrypts the user information
according to the challenge issued by the SIP server and sends the
response to the SIP server. The SIP server attempts to validate the
user's credentials, but they are not valid (the user's password does
not match the password established for the user's account). The
server returns a response (401 Unauthorized) to User B's SIP client.
Message Details
F1 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F2 Unauthorized SIP Server -> User B
SIP/2.0 401 Unauthorized
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
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SIP Basic Call Flow Examples October 2002
From: LittleGuy <sip:UserB@biloxi.com>;tag=a73kszlfl
To: LittleGuy <sip:UserB@biloxi.com>;tag=1410948204
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 1 REGISTER
WWW-Authenticate: Digest realm="atlanta.com", qop="auth",
nonce="f1cec4341ae6ca9c8e88df84be55a359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F3 REGISTER B -> SIP Server
REGISTER sip:ss2.biloxi.com SIP/2.0
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=JueHGuidj28dfga
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 2 REGISTER
Contact: <sip:UserB@client.biloxi.com>
Authorization: Digest username="UserB", realm="atlanta.com",
nonce="f1cec4341ae6ca9c8e88df84be55a359", opaque="",
uri="sip:ss2.biloxi.com",
response="61f8470ceb87d7ebf508220214ed438b"
Content-Length: 0
/* The response above encodes the incorrect password */
F4 401 Unauthorized SIP Server -> User B
SIP/2.0 401 Unauthorized
Via: SIP/2.0/TLS client.biloxi.com:5061;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=JueHGuidj28dfga
To: LittleGuy <sip:UserB@biloxi.com>;tag=1410948204
Call-ID: 1j9FpLxk3uxtm8tn@biloxi.com
CSeq: 2 REGISTER
WWW-Authenticate: Digest realm="atlanta.com", qop="auth",
nonce="84f1c1ae6cbe5ua9c8e88dfa3ecm3459",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
3. SIP Session Establishment
This section details session establishment between two SIP User
Agents (UAs): User A and User B. User A (LittleGuy
sip:UserA@atlanta.com) and User B (BigGuy sip:UserB@biloxi.com) are
assumed to be SIP phones or SIP-enabled devices. The successful
calls show the initial signaling, the exchange of media information
in the form of SDP payloads, the establishment of the media session,
then finally the termination of the call.
HTTP Digest authentication is used by Proxy Servers to authenticate
the caller User A. It is assumed that User B has registered with
Proxy Server Proxy 2 as per Section 2 to be able to receive the calls
via the Proxy.
3.1 Successful Session Establishment
User A User B
| |
| INVITE F1 |
|----------------------->|
| 180 Ringing F2 |
|<-----------------------|
| |
| 200 OK F3 |
|<-----------------------|
| ACK F4 |
|----------------------->|
| Both Way RTP Media |
|<======================>|
| |
| BYE F5 |
|<-----------------------|
| 200 OK F6 |
|----------------------->|
| |
In this scenario, User A completes a call to User B directly.
Message Details
F1 INVITE User A -> User B
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
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SIP Basic Call Flow Examples October 2002
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F2 180 Ringing User B -> User A
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=8321234356
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
Content-Length: 0
F3 200 OK User B -> User A
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=8321234356
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
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SIP Basic Call Flow Examples October 2002
a=rtpmap:0 PCMU/8000
F4 ACK User A -> User B
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bd5
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=8321234356
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* RTP streams are established between A and B */
/* User B Hangs Up with User A. Note that the CSeq is NOT 2, since
User A and User B maintain their own independent CSeq counts.
(The INVITE was request 1 generated by User A, and the BYE is
request 1 generated by User B) */
F5 BYE User B -> User A
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=8321234356
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F6 200 OK User A -> User B
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=8321234356
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
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SIP Basic Call Flow Examples October 2002
3.2 Session Establishment Through Two Proxies
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| | |
| 407 F2 | | |
|<---------------| | |
| ACK F3 | | |
|--------------->| | |
| INVITE F4 | | |
|--------------->| INVITE F5 | |
| 100 F6 |--------------->| INVITE F7 |
|<---------------| 100 F8 |--------------->|
| |<---------------| |
| | | 180 F9 |
| | 180 F10 |<---------------|
| 180 F11 |<---------------| |
|<---------------| | 200 F12 |
| | 200 F13 |<---------------|
| 200 F14 |<---------------| |
|<---------------| | |
| ACK F15 | | |
|--------------->| ACK F16 | |
| |--------------->| ACK F17 |
| | |--------------->|
| Both Way RTP Media |
|<================================================>|
| | | BYE F18 |
| | BYE F19 |<---------------|
| BYE F20 |<---------------| |
|<---------------| | |
| 200 F21 | | |
|--------------->| 200 F22 | |
| |--------------->| 200 F23 |
| | |--------------->|
| | | |
In this scenario, User A completes a call to User B using two proxies
Proxy 1 and Proxy 2. The initial INVITE (F1) contains a pre-loaded
Route header with the address of Proxy 1 (Proxy 1 is configured as a
default outbound proxy for User A). The request does not contain the
Authorization credentials Proxy 1 requires, so a 407 Proxy
Authorization response is sent containing the challenge information.
A new INVITE (F4) is then sent containing the correct credentials and
the call proceeds. The call terminates when User B disconnects by
initiating a BYE message.
Johnston et al Expires - April 2002 [Page 18]
SIP Basic Call Flow Examples October 2002
Proxy 1 inserts a Record-Route header into the INVITE message to
ensure that it is present in all subsequent message exchanges. Proxy
2 also inserts itself into the Record-Route header. The ACK (F15)
and BYE (F18) both have a Route header.
Message Details
F1 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b43
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 1 challenges User A for authentication */
F2 407 Proxy Authorization Required Proxy 1 -> User A
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b43
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=3flal12sf
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 INVITE
Proxy-Authenticate: Digest realm="atlanta.com", qop="auth",
nonce="f84f1cec41e6cbe5aea9c8e88d359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
Johnston et al Expires - April 2002 [Page 19]
SIP Basic Call Flow Examples October 2002
F3 ACK A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b43
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=3flal12sf
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* User A responds be re-sending the INVITE with authentication
credentials in it. */
F4 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="wf84f1ceczx41ae6cbe5aea9c8e88d359", opaque="",
uri="sip:UserB@biloxi.com", response="42ce3cef44b22f50c6a6071bc8"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 1 accepts the credentials and forwards the INVITE to Proxy
2. Proxy 1 is assumed to have been authenticated by Proxy 2 using
IPSec. Client for A prepares to receive data on port 49172 from the
network. */
F5 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Johnston et al Expires - April 2002 [Page 20]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F6 100 Trying Proxy 1 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Content-Length: 0
F7 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Johnston et al Expires - April 2002 [Page 21]
SIP Basic Call Flow Examples October 2002
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F8 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Content-Length: 0
F9 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F10 180 Ringing Proxy 2 -> Proxy 1
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Johnston et al Expires - April 2002 [Page 22]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F11 180 Ringing Proxy 1 -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
CSeq: 2 INVITE
Content-Length: 0
F12 200 OK B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
Johnston et al Expires - April 2002 [Page 23]
SIP Basic Call Flow Examples October 2002
a=rtpmap:0 PCMU/8000
F13 200 OK Proxy 2 -> Proxy 1
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F14 200 OK Proxy 1 -> A
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Johnston et al Expires - April 2002 [Page 24]
SIP Basic Call Flow Examples October 2002
F15 ACK A -> Proxy 1
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b76
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>, <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 ACK
Content-Length: 0
F16 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b76
;received=192.0.2.101
Max-Forwards: 69
Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 ACK
Content-Length: 0
F17 ACK Proxy 2 -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74b76
;received=192.0.2.101
Max-Forwards: 68
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 3848276298220188511@atlanta.com
CSeq: 2 ACK
Content-Length: 0
/* RTP streams are established between A and B */
/* User B Hangs Up with User A. */
Johnston et al Expires - April 2002 [Page 25]
SIP Basic Call Flow Examples October 2002
/* Again, note that the CSeq is NOT 3. User A and User B maintain
their own separate CSeq counts */
F18 BYE User B -> Proxy 2
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
Max-Forwards: 70
Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F19 BYE Proxy 2 -> Proxy 1
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
Max-Forwards: 69
Route: <sip:ss1.atlanta.com;lr>
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F20 BYE Proxy 1 -> User A
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
Max-Forwards: 68
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F21 200 OK User A -> Proxy 1
Johnston et al Expires - April 2002 [Page 26]
SIP Basic Call Flow Examples October 2002
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F22 200 OK Proxy 1 -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.101
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F23 200 OK Proxy 2 -> User B
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.com
CSeq: 1 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 27]
SIP Basic Call Flow Examples October 2002
3.3 Session with Multiple Proxy Authentication
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|----------->| | |
| 407 Proxy Authorization Required F2 |
|<-----------| | |
| ACK F3 | | |
|----------->| | |
| INVITE F4 | | |
|----------->| | |
| 100 F5 | | |
|<-----------| INVITE F6 | |
| |---------->| |
| | 407 Proxy Authorization Required F7
| |<----------| |
| | ACK F8 | |
| |---------->| |
| 407 Proxy Authorization Required F9 |
|<-----------| | |
| ACK F10 | | |
|----------->| | |
| INVITE F11| | |
|----------->| | |
| 100 F12 | | |
|<-----------| INVITE F13| |
| |---------->| |
| | 100 F14 | |
| |<----------| INVITE F15 |
| | |------------>|
| | | 200 OK F16 |
| | 200 OK F17|<------------|
| 200 OK F18 |<----------| |
|<-----------| | |
| ACK F19 | | |
|----------->| ACK F20 | |
| |---------->| ACK F21 |
| | |------------>|
| RTP Media Path |
|<====================================>|
In this scenario, User A completes a call to User B using two proxies
Proxy 1 and Proxy 2. User A has valid credentials in both domains.
Since the initial INVITE (F1) does not contain the
Authorization credentials Proxy 1 requires, so a 407 Proxy
Authorization response is sent containing the challenge information.
A new INVITE (F4) is then sent containing the correct credentials and
Johnston et al Expires - April 2002 [Page 28]
SIP Basic Call Flow Examples October 2002
the call proceeds after Proxy 2 challenges and receives valid
credentials. The call terminates when User B disconnects by
initiating a BYE message.
Proxy 1 inserts a Record-Route header into the INVITE message to
ensure that it is present in all subsequent message exchanges. Proxy
2 also inserts itself into the Record-Route header.
Message Details
F1 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b03
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 1 challenges User A for authentication */
F2 407 Proxy Authorization Required Proxy 1 -> User A
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b03
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=876321
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Proxy-Authenticate: Digest realm="atlanta.com", qop="auth",
nonce="wf84f1cczx41ae6cbeaea9ce88d359",
Johnston et al Expires - April 2002 [Page 29]
SIP Basic Call Flow Examples October 2002
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F3 ACK A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Max-Forwards: 70
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b03
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=876321
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* User A responds be re-sending the INVITE with authentication
credentials in it. The same Call-ID is used, so the CSeq is
increased. */
F4 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="wf84f1ceczx41ae6cbe5aea9c8e88d359", opaque="",
uri="sip:UserB@biloxi.com", response="42ce3cef44b22f50c6a6071bc8"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 1 accepts the credentials and forwards the INVITE to Proxy
2. Proxy 1 is assumed to have been authenticated by Proxy 2 using
IPSec. Client for A prepares to receive data on port 49172 from the
Johnston et al Expires - April 2002 [Page 30]
SIP Basic Call Flow Examples October 2002
network. */
F5 100 Trying Proxy 1 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Content-Length: 0
F6 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 2 challenges User A for authentication */
F7 407 Proxy Authorization Required Proxy 2 -> Proxy 1
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Johnston et al Expires - April 2002 [Page 31]
SIP Basic Call Flow Examples October 2002
To: LittleGuy <sip:UserB@biloxi.com>;tag=838209
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Proxy-Authenticate: Digest realm="biloxi.com", qop="auth",
nonce="c1e22c41ae6cbe5ae983a9c8e88d359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F8 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=838209
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 ACK
Content-Length: 0
/* Proxy 1 forwards the challenge to User A for authentication from
Proxy 2 */
F9 407 Proxy Authorization Required Proxy 1 -> User A
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=838209
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Proxy-Authenticate: Digest realm="biloxi.com", qop="auth",
nonce="c1e22c41ae6cbe5ae983a9c8e88d359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F10 ACK User A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b21
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=838209
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 ACK
Content-Length: 0
Johnston et al Expires - April 2002 [Page 32]
SIP Basic Call Flow Examples October 2002
/* User A responds be re-sending the INVITE with authentication
credentials for Proxy 1 AND Proxy 2. */
F11 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="wf84f1ceczx41ae6cbe5aea9c8e88d359", opaque="",
uri="sip:UserB@biloxi.com", response="42ce3cef44b22f50c6a6071bc8"
Proxy-Authorization: Digest username="UserA", realm="biloxi.com",
nonce="c1e22c41ae6cbe5ae983a9c8e88d359", opaque="",
uri="sip:UserB@biloxi.com", response="f44ab22f150c6a56071bce8"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 1 finds its credentials and authorizes User A, forwarding
the INVITE to Proxy. */
F12 100 Trying Proxy 1 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 33]
SIP Basic Call Flow Examples October 2002
F13 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="biloxi.com",
nonce="c1e22c41ae6cbe5ae983a9c8e88d359", opaque="",
uri="sip:UserB@biloxi.com", response="f44ab22f150c6a56071bce8"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 2 finds its credentials and authorizes User A, forwarding
the INVITE to User B. */
F14 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Content-Length: 0
F15 INVITE Proxy 2 -> User B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK31972.1
Johnston et al Expires - April 2002 [Page 34]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* User B answers the call immediately */
F16 200 OK User B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK31972.1
;received=192.0.2.222
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
Johnston et al Expires - April 2002 [Page 35]
SIP Basic Call Flow Examples October 2002
a=rtpmap:0 PCMU/8000
F17 200 OK Proxy 2 -> Proxy 1
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F18 200 OK Proxy 1 -> User A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Johnston et al Expires - April 2002 [Page 36]
SIP Basic Call Flow Examples October 2002
F19 ACK User A -> Proxy 1
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b44
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>, <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 ACK
Content-Length: 0
F20 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b44
;received=192.0.2.101
Max-Forwards: 69
Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 ACK
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F21 ACK Proxy 2 -> User A
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK31972.1
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK230f2.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b44
;received=192.0.2.101
Max-Forwards: 68
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=9103874
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 3 ACK
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
Johnston et al Expires - April 2002 [Page 37]
SIP Basic Call Flow Examples October 2002
3.4 Successful Session with Proxy Failure
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| | |
| INVITE F2 | | |
|--------------->| | |
| INVITE F3 | | |
|--------------->| | |
| INVITE F4 | | |
|--------------->| | |
| INVITE F5 | | |
|--------------->| | |
| INVITE F6 | | |
|--------------->| | |
| INVITE F7 | | |
|--------------->| | |
| INVITE F8 | |
|-------------------------------->| |
| 407 F9 | |
|<--------------------------------| |
| ACK F10 | |
|-------------------------------->| |
| INVITE F11 | |
|-------------------------------->| INVITE F12 |
| 100 F13 |--------------->|
|<--------------------------------| |
| | 180 F14 |
| 180 F15 |<---------------|
|<--------------------------------| |
| | 200 F16 |
| 200 F17 |<---------------|
|<--------------------------------| |
| ACK F18 | |
|-------------------------------->| ACK F19 |
| |--------------->|
| Both Way RTP Media |
|<================================================>|
| | BYE F20 |
| BYE F21 |<---------------|
|<--------------------------------| |
| 200 F22 | |
|-------------------------------->| 200 F23 |
| |--------------->|
| | |
Johnston et al Expires - April 2002 [Page 38]
SIP Basic Call Flow Examples October 2002
In this scenario, User A completes a call to User B via a Proxy
Server. User A is configured for a primary SIP Proxy Server Proxy 1
and a secondary SIP Proxy Server Proxy 2 (Or is able to use DNS SRV
records to locate Proxy 1 and Proxy 2). User A has valid credentials
for both domains. Proxy 1 is out of service and does not respond to
INVITEs (it is reachable, but unresponsive). User A then completes
the call to User B using Proxy 2.
Message Details
F1 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK465b6d
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F2 INVITE A -> Proxy 1
Same as Message F1
F3 INVITE A -> Proxy 1
Same as Message F1
F4 INVITE A -> Proxy 1
Same as Message F1
Johnston et al Expires - April 2002 [Page 39]
SIP Basic Call Flow Examples October 2002
F5 INVITE A -> Proxy 1
Same as Message F1
F6 INVITE A -> Proxy 1
Same as Message F1
F7 INVITE A -> Proxy 1
Same as Message F1
/* User A gives up on the unresponsive proxy */
F8 INVITE A -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b8a
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Proxy 2 challenges User A for authentication */
F9 407 Proxy Authorization Required Proxy 2 -> User A
SIP/2.0 407 Proxy Authorization Required
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b8a
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Johnston et al Expires - April 2002 [Page 40]
SIP Basic Call Flow Examples October 2002
To: LittleGuy <sip:UserB@biloxi.com>;tag=2421452
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 INVITE
Proxy-Authenticate: Digest realm="biloxi.com", qop="auth",
nonce="1ae6cbe5ea9c8e8df84fqnlec434a359",
opaque="", stale=FALSE, algorithm=MD5
Content-Length: 0
F10 ACK A -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b8a
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=2421452
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* User A responds be re-sending the INVITE with authentication
credentials in it. */
F11 INVITE A -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="biloxi.com",
nonce="1ae6cbe5ea9c8e8df84fqnlec434a359", opaque="",
uri="sip:UserB@biloxi.com",
response="8a880c919d1a52f20a1593e228adf599"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Johnston et al Expires - April 2002 [Page 41]
SIP Basic Call Flow Examples October 2002
/* Proxy 2 accepts the credentials and forwards the INVITE to User B.
Client for A prepares to receive data on port 49172 from the network.
*/
F12 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F13 100 Trying Proxy 2 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Content-Length: 0
F14 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Johnston et al Expires - April 2002 [Page 42]
SIP Basic Call Flow Examples October 2002
Record-Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F15 180 Ringing Proxy 2 -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F16 200 OK B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F17 200 OK Proxy 2 -> A
Johnston et al Expires - April 2002 [Page 43]
SIP Basic Call Flow Examples October 2002
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F18 ACK A -> Proxy 2
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b8g
Max-Forwards: 70
Route: <sip:ss2.biloxi.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 ACK
Content-Length: 0
F19 ACK Proxy 2 -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b8g
;received=192.0.2.101
Max-Forwards: 69
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 2 ACK
Content-Length: 0
Johnston et al Expires - April 2002 [Page 44]
SIP Basic Call Flow Examples October 2002
/* RTP streams are established between A and B */
/* User B Hangs Up with User A. */
F20 BYE User B -> Proxy 2
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/UDP client.biloxi.com:5060;branch=z9hG4bKnashds7
Max-Forwards: 70
Route: <sip:ss2.biloxi.com;lr>
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F21 BYE Proxy 2 -> User A
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
Max-Forwards: 69
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F22 200 OK User A -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP client.biloxi.com:5060;branch=z9hG4bKnashds7
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F23 200 OK Proxy 2 -> User B
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.biloxi.com:5060;branch=z9hG4bKnashds7
Johnston et al Expires - April 2002 [Page 45]
SIP Basic Call Flow Examples October 2002
;received=192.0.2.201
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 4Fde34wkd11wsGFDs3@atlanta.com
CSeq: 1 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 46]
SIP Basic Call Flow Examples October 2002
3.5 Session Through a SIP ALG
User A ALG Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| INVITE F2 | |
| 100 F3 |--------------->| INVITE F4 |
|<---------------| 100 F5 |--------------->|
| |<---------------| 180 F6 |
| | 180 F7 |<---------------|
| 180 F8 |<---------------| |
|<---------------| | 200 F9 |
| | 200 F10 |<---------------|
| 200 F11 |<---------------| |
|<---------------| |
| ACK F12 | |
|--------------->| ACK F13 |
| |-------------------------------->|
| RTP Media | Both Way RTP Media |
|<==============>|<===============================>|
| BYE F14 | |
|--------------->| BYE F15 |
| |-------------------------------->|
| | 200 F16 |
| 200 F17 |<--------------------------------|
|<---------------| |
| | |
User A completes a call to User B through a ALG (Application Layer
Gateway) and a SIP Proxy. The routing through the ALG is
accomplished using a pre-loaded Route header in the INVITE F1. Note
that the media stream setup is not end-to-end - the ALG terminates
both media streams and bridges them. This is done by the ALG
modifying the SDP in the INVITE (F1) and 200 OK (F10) messages, and
possibly any 18x or ACK messages containing SDP.
In addition to firewall traversal, this Back-to-Back User Agent
(B2BUA) could be used as part of an anonymizer
service (in which all identifying information on User A would be
removed), or to perform codec media conversion, such as mu-law to A-
law conversion of PCM on an international call.
Also note that Proxy 2 does not Record-Route in this call flow.
Message Details
Johnston et al Expires - April 2002 [Page 47]
SIP Basic Call Flow Examples October 2002
F1 INVITE A -> SIP ALG
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Route: <sip:alg1.atlanta.com;lr>
Proxy-Authorization: Digest username="UserA", realm="biloxi.com",
nonce="85b4f1cen4341ae6cbe5a3a9c8e88df9", opaque="",
uri="sip:UserB@biloxi.com",
response="b3f392f9218a328b9294076d708e6815"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* Client for A prepares to receive data on port 49172 from the
network. */
F2 INVITE SIP ALG -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="biloxi.com",
nonce="85b4f1cen4341ae6cbe5a3a9c8e88df9", opaque="",
uri="sip:UserB@biloxi.com",
response="b3f392f9218a328b9294076d708e6815"
Content-Type: application/sdp
Content-Length: 142
Johnston et al Expires - April 2002 [Page 48]
SIP Basic Call Flow Examples October 2002
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.128
t=0 0
m=audio 2000 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying SIP ALG -> A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
/* SIP ALG prepares to proxy data from port 192.0.2.128/2000 to
192.0.2.101/49172. Proxy 2 uses a Location Service function to
determine where B is located. Based upon location analysis the call
is forwarded to User B */
F4 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 142
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.128
Johnston et al Expires - April 2002 [Page 49]
SIP Basic Call Flow Examples October 2002
t=0 0
m=audio 2000 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F5 100 Trying Proxy 2 -> SIP ALG
SIP/2.0 100 Trying
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F6 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.222
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F7 180 Ringing Proxy 2 -> SIP ALG
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Johnston et al Expires - April 2002 [Page 50]
SIP Basic Call Flow Examples October 2002
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F8 180 Ringing SIP ALG -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F9 200 OK B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.222
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F10 200 OK Proxy 2 -> SIP ALG
SIP/2.0 200 OK
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
Johnston et al Expires - April 2002 [Page 51]
SIP Basic Call Flow Examples October 2002
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F11 200 OK SIP ALG -> A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.128
t=0 0
m=audio 1734 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* The ALG prepares to proxy packets from 192.0.2.128/
1734 to 192.0.2.201/3456 */
F12 ACK A -> SIP ALG
Johnston et al Expires - April 2002 [Page 52]
SIP Basic Call Flow Examples October 2002
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bhh
Max-Forwards: 70
Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F13 ACK SIP ALG -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bhh
;received=192.0.2.101
Max-Forwards: 69
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* RTP streams are established between A and the ALG and
between the ALG and B*/
/* User A Hangs Up with User B. */
F14 BYE A -> SIP ALG
BYE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74be5
Max-Forwards: 70
Route: <sip:alg1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
F15 BYE SIP ALG -> B
BYE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74be5
;received=192.0.2.101
Johnston et al Expires - April 2002 [Page 53]
SIP Basic Call Flow Examples October 2002
Max-Forwards: 69
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
F16 200 OK B -> SIP ALG
SIP/2.0 200 OK
Via: SIP/2.0/UDP alg1.atlanta.com:5060;branch=z9hG4bK739578.1
;received=192.0.2.128
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74be5
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
F17 200 OK SIP ALG -> A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74be5
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 54]
SIP Basic Call Flow Examples October 2002
3.6 Session via Redirect and Proxy Servers with SDP in ACK
User A Redirect Server Proxy 3 User B
| | | |
| INVITE F1 | | |
|--------------->| | |
| 302 F2 | | |
|<---------------| | |
| ACK F3 | | |
|--------------->| | |
| INVITE F4 | |
|-------------------------------->| INVITE F5 |
| 100 F6 |--------------->|
|<--------------------------------| 180 F7 |
| 180 F8 |<---------------|
|<--------------------------------| |
| | 200 F9 |
| 200 F10 |<---------------|
|<--------------------------------| |
| ACK F11 | |
|-------------------------------->| ACK F12 |
| |--------------->|
| Both Way RTP Media |
|<================================================>|
| | BYE F13 |
| BYE F14 |<---------------|
|<--------------------------------| |
| 200 F15 | |
|-------------------------------->| 200 F16 |
| |--------------->|
| | |
In this scenario, User A places a call to User B using first a
Redirect server then a Proxy Server. The INVITE message is first
sent to the Redirect Server. The Server returns a 302 Moved
Temporarily response (F2) containing a Contact header with User B's
current SIP address. User A then generates a new INVITE and sends to
User B via the Proxy Server and the call proceeds normally. In this
example, no SDP is present in the INVITE, so the SDP is carried in
the ACK message.
The call is terminated when User B sends a BYE message.
Message Details
F1 INVITE A -> Redirect Server
Johnston et al Expires - April 2002 [Page 55]
SIP Basic Call Flow Examples October 2002
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bKbf9f44
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Length: 0
F2 302 Moved Temporarily Redirect Proxy -> A
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bKbf9f44
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=53fHlqlQ2
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@chicago.com;transport=tcp>
Content-Length: 0
F3 ACK A -> Redirect Server
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bKbf9f44
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=53fHlqlQ2
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F4 INVITE A -> Proxy 3
INVITE sip:UserB@chicago.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Length: 0
Johnston et al Expires - April 2002 [Page 56]
SIP Basic Call Flow Examples October 2002
F5 INVITE Proxy 3 -> B
INVITE sip:UserB@client.chicago.com SIP/2.0
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Length: 0
F6 100 Trying Proxy 3 -> A
SIP/2.0 100 Trying
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Content-Length: 0
F7 180 Ringing B -> Proxy 3
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.233
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.chicago.com;transport=tcp>
Content-Length: 0
F8 180 Ringing Proxy 3 -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Johnston et al Expires - April 2002 [Page 57]
SIP Basic Call Flow Examples October 2002
;received=192.0.2.101
Record-Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.chicago.com;transport=tcp>
Content-Length: 0
F9 200 OK B -> Proxy 3
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.233
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.chicago.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 142
v=0
o=UserB 2890844527 2890844527 IN IP4 client.chicago.com
s=-
c=IN IP4 192.0.2.100
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F10 200 OK Proxy -> A
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 INVITE
Contact: <sip:UserB@client.chicago.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 142
Johnston et al Expires - April 2002 [Page 58]
SIP Basic Call Flow Examples October 2002
v=0
o=UserB 2890844527 2890844527 IN IP4 client.chicago.com
s=-
c=IN IP4 192.0.2.100
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* ACK contains SDP of A since none present in INVITE */
F11 ACK A -> Proxy 3
ACK sip:UserB@client.chicago.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bq9
Max-Forwards: 70
Route: <sip:ss3.chicago.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 ACK
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F12 ACK Proxy 3 -> B
ACK sip:UserB@client.chicago.com SIP/2.0
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bq9
;received=192.0.2.101
Max-Forwards: 69
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 ACK
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
Johnston et al Expires - April 2002 [Page 59]
SIP Basic Call Flow Examples October 2002
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/* RTP streams are established between A and B*/
/* User B Hangs Up with User A. */
F13 BYE B -> Proxy 3
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP client.chicago.com:5060;branch=z9hG4bKfgaw2
Max-Forwards: 70
Route: <sip:ss3.chicago.com;lr>
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F14 BYE Proxy 3 -> A
BYE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.100
Via: SIP/2.0/TCP client.chicago.com:5060;branch=z9hG4bKfgaw2
Max-Forwards: 69
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 BYE
Content-Length: 0
F15 200 OK A -> Proxy 3
SIP/2.0 200 OK
Via: SIP/2.0/TCP ss3.chicago.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.233
Via: SIP/2.0/TCP client.chicago.com:5060;branch=z9hG4bKfgaw2
;received=192.0.2.100
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 60]
SIP Basic Call Flow Examples October 2002
F16 200 OK Proxy 3 -> B
SIP/2.0 200 OK
Via: SIP/2.0/TCP client.chicago.com:5060;branch=z9hG4bKfgaw2
;received=192.0.2.100
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 61]
SIP Basic Call Flow Examples October 2002
3.7 Session with re-INVITE (IP Address Change)
User A Proxy 2 User B
| F1 INVITE | |
|------------------->| F2 INVITE |
| F3 100 Trying |------------------->|
|<-------------------| F4 180 Ringing |
| F5 180 Ringing |<-------------------|
|<-------------------| |
| | F6 200 OK |
| F7 200 OK |<-------------------|
|<-------------------| |
| F8 ACK |
|---------------------------------------->|
| Both Way RTP Media Established |
|<=======================================>|
| |
| B changes IP address |
| |
| F9 INVITE |
|<----------------------------------------|
| F10 200 OK |
|---------------------------------------->|
| F11 ACK |
|<----------------------------------------|
| New RTP Media Stream |
|<=======================================>|
| F12 BYE |
|---------------------------------------->|
| F25 200 OK |
|<----------------------------------------|
| |
This example shows a session in which the media is changes midway
through the session. When User BÆs IP address changes during the
session, User B sends a re-INVITE containing a new Contact and SDP
(version number incremented) information to A. In this flow, the
proxy does not Record-Route so is not in the SIP messaging path after
the initial exchange.
Message Details
F1 INVITE A -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Johnston et al Expires - April 2002 [Page 62]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F2 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying Proxy 2 -> A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Johnston et al Expires - April 2002 [Page 63]
SIP Basic Call Flow Examples October 2002
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F4 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.222
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F5 180 Ringing Proxy 2 -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F6 200 OK B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.222
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
Johnston et al Expires - April 2002 [Page 64]
SIP Basic Call Flow Examples October 2002
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F7 200 OK Proxy 2 -> A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Type: application/sdp
Content-Length: 141
v=0
o=UserB 2890844527 2890844527 IN IP4 client.biloxi.com
s=-
c=IN IP4 192.0.2.201
t=0 0
m=audio 3456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F8 ACK A -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74b7b
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
/* RTP streams are established between A and B */
/* B changes IP address and re-INVITEs A with new Contact and SDP */
F9 INVITE B -> A
Johnston et al Expires - April 2002 [Page 65]
SIP Basic Call Flow Examples October 2002
INVITE sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/UDP client.chicago.com:5060;branch=z9hG4bKlkld5l
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 14 INVITE
Contact: <sip:UserB@client.chicago.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserB 2890844527 2890844528 IN IP4 client.chicago.com
s=-
c=IN IP4 192.0.2.100
t=0 0
m=audio 47172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F10 200 OK A ->B
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.chicago.com:5060;branch=z9hG4bKlkld5l
;received=192.0.2.100
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 14 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 1000 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F11 ACK B -> A
ACK sip:UserA@client.atlanta.com SIP/2.0
Via: SIP/2.0/UDP client.chicago.com:5060;branch=z9hG4bKlkldcc
Max-Forwards: 70
From: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Johnston et al Expires - April 2002 [Page 66]
SIP Basic Call Flow Examples October 2002
To: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 14 ACK
Content-Length: 0
/* New RTP stream established between A and B */
/* A hangs up with B */
F12 BYE A -> B
BYE sip:UserB@client.chicago.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bo4
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
F13 200 OK B -> A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bo4
;received=192.0.2.101
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 2 BYE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 67]
SIP Basic Call Flow Examples October 2002
3.8 Unsuccessful No Answer
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| INVITE F2 | |
| 100 F3 |--------------->| INVITE F4 |
|<---------------| 100 F5 |--------------->|
| |<---------------| |
| | | 180 F6 |
| | 180 F7 |<---------------|
| 180 F8 |<---------------| |
|<---------------| | |
| | | |
| CANCEL F9 | | |
|--------------->| | |
| 200 F10 | | |
|<---------------| CANCEL F11 | |
| |--------------->| |
| | 200 F12 | |
| |<---------------| |
| | | CANCEL F13 |
| | |--------------->|
| | | 200 F14 |
| | |<---------------|
| | | 487 F15 |
| | |<---------------|
| | | ACK F16 |
| | 487 F17 |--------------->|
| |<---------------| |
| | ACK F18 | |
| 487 F19 |--------------->| |
|<---------------| | |
| ACK F20 | | |
|--------------->| | |
| | | |
In this scenario, User A gives up on the call before User B answers
(sends a 200 OK response). User A sends a CANCEL (F9) since no final
response had been received from User B. If a 200 OK to the INVITE
had crossed with the CANCEL, User A would have sent an ACK then a BYE
to User B in order to properly terminate the call.
Note that the CANCEL message is acknowledged with a 200 OK on a hop
by hop basis, rather than end to end.
Johnston et al Expires - April 2002 [Page 68]
SIP Basic Call Flow Examples October 2002
Message Details
F1 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="ze7k1ee88df84f1cec431ae6cbe5a359", opaque="",
uri="sip:UserB@biloxi.com",
response="b00b416324679d7e243f55708d44be7b"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/*Client for A prepares to receive data on port 49172 from the
network.*/
F2 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
Johnston et al Expires - April 2002 [Page 69]
SIP Basic Call Flow Examples October 2002
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying Proxy 1 -> A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F4 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.client.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
Max-Forwards: 68
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Johnston et al Expires - April 2002 [Page 70]
SIP Basic Call Flow Examples October 2002
F5 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F6 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss2.client.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F7 180 Ringing Proxy 2 -> Proxy 1
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F8 180 Ringing Proxy 1 -> A
Johnston et al Expires - April 2002 [Page 71]
SIP Basic Call Flow Examples October 2002
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F9 CANCEL A -> Proxy 1
CANCEL sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
F10 200 OK Proxy 1 -> A
SIP/2.0 200 OK
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
F11 CANCEL Proxy 1 -> Proxy 2
CANCEL sip:UserA@atlanta.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
Johnston et al Expires - April 2002 [Page 72]
SIP Basic Call Flow Examples October 2002
F12 200 OK Proxy 2 -> Proxy 1
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
F13 CANCEL Proxy 2 -> B
CANCEL sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
F14 200 OK B -> Proxy 2
SIP/2.0 200 OK
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 CANCEL
Content-Length: 0
F15 487 Request Terminated B -> Proxy 2
SIP/2.0 487 Request Terminated
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Johnston et al Expires - April 2002 [Page 73]
SIP Basic Call Flow Examples October 2002
Content-Length: 0
F16 ACK Proxy 2 -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F17 487 Request Terminated Proxy 2 -> Proxy 1
SIP/2.0 487 Request Terminated
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F18 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F19 487 Request Terminated Proxy 1 -> A
SIP/2.0 487 Request Terminated
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
Johnston et al Expires - April 2002 [Page 74]
SIP Basic Call Flow Examples October 2002
CSeq: 1 INVITE
F20 ACK A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
Johnston et al Expires - April 2002 [Page 75]
SIP Basic Call Flow Examples October 2002
3.9 Unsuccessful Busy
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| INVITE F2 | |
| 100 F3 |--------------->| INVITE F4 |
|<---------------| 100 F5 |--------------->|
| |<---------------| |
| | | 486 F6 |
| | |<---------------|
| | | ACK F7 |
| | 486 F8 |--------------->|
| |<---------------| |
| | ACK F9 | |
| 486 F10 |--------------->| |
|<---------------| | |
| ACK F11 | | |
|--------------->| | |
| | | |
In this scenario, User B is busy and sends a 486 Busy Here response
to User A's INVITE. Note that the non-2xx response is acknowledged
on a hop-by-hop basis instead of end-to-end. Also note that many SIP
UAs will not return a 486 response, as they have multiple line and
other features.
Message Details
F1 INVITE User A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="dc3a5ab2530aa93112cf5904ba7d88fa", opaque="",
uri="sip:UserB@biloxi.com",
response="702138b27d869ac8741e10ec643d55be"
Content-Type: application/sdp
Content-Length: 143
Johnston et al Expires - April 2002 [Page 76]
SIP Basic Call Flow Examples October 2002
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/*Client for A prepares to receive data on port 49172 from the
network.*/
F2 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying Proxy 1 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 77]
SIP Basic Call Flow Examples October 2002
F4 INVITE Proxy 2 -> User B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com;transport=tcp>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F5 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F6 486 Busy Here User B -> Proxy 2
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Johnston et al Expires - April 2002 [Page 78]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F7 ACK Proxy 2 -> User B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F8 486 Busy Here Proxy 2 -> Proxy 1
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F9 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F10 486 Busy Here Proxy 1 -> User A
Johnston et al Expires - April 2002 [Page 79]
SIP Basic Call Flow Examples October 2002
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F11 ACK User A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/TCP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
Johnston et al Expires - April 2002 [Page 80]
SIP Basic Call Flow Examples October 2002
3.10 Unsuccessful No Response from User Agent
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| INVITE F2 | |
| 100 F3 |--------------->| INVITE F4 |
|<---------------| 100 F5 |--------------->|
| |<---------------| INVITE F6 |
| | |--------------->|
| | | INVITE F7 |
| | |--------------->|
| | | INVITE F8 |
| | |--------------->|
| | | INVITE F9 |
| | |--------------->|
| | | INVITE F10 |
| | |--------------->|
| | | INVITE F11 |
| | 480 F12 |--------------->|
| |<---------------| |
| | ACK F13 | |
| 480 F14 |--------------->| |
|<---------------| | |
| ACK F15 | | |
|--------------->| | |
| | | |
In this example, there is no response from User B to User A's INVITE
messages being re-transmitted by Proxy 2. After the sixth re-
transmission, Proxy 2 gives up and sends a 480 No Response to User A.
Message Details
F1 INVITE User A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="cf5904ba7d8dc3a5ab2530aa931128fa", opaque="",
Johnston et al Expires - April 2002 [Page 81]
SIP Basic Call Flow Examples October 2002
uri="sip:UserB@biloxi.com",
response="7afc04be7961f053c24f80e7dbaf888f"
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/*Client for A prepares to receive data on port 49172 from the
network.*/
F2 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying Proxy 1 -> User A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Johnston et al Expires - April 2002 [Page 82]
SIP Basic Call Flow Examples October 2002
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F4 INVITE Proxy 2 -> User B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F5 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F6 INVITE Proxy 2 -> User B
Resend of Message F4
Johnston et al Expires - April 2002 [Page 83]
SIP Basic Call Flow Examples October 2002
F7 INVITE Proxy 2 -> User B
Resend of Message F4
F8 INVITE Proxy 2 -> User B
Resend of Message F4
F9 INVITE Proxy 2 -> User B
Resend of Message F4
F10 INVITE Proxy 2 -> User B
Resend of Message F4
F11 INVITE Proxy 2 -> User B
Resend of Message F4
/* Proxy 2 gives up */
F12 480 No Response Proxy 2 -> Proxy 1
SIP/2.0 480 No Response
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F13 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
Johnston et al Expires - April 2002 [Page 84]
SIP Basic Call Flow Examples October 2002
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F14 480 No Response Proxy 1 -> User A
SIP/2.0 480 No Response
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F15 ACK User A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
Johnston et al Expires - April 2002 [Page 85]
SIP Basic Call Flow Examples October 2002
3.11 Unsuccessful Temporarily Unavailable
User A Proxy 1 Proxy 2 User B
| | | |
| INVITE F1 | | |
|--------------->| INVITE F2 | |
| 100 F3 |--------------->| INVITE F4 |
|<---------------| 100 F5 |--------------->|
| |<---------------| 180 F6 |
| | 180 F7 |<---------------|
| 180 F8 |<---------------| |
|<---------------| | 480 F9 |
| | |<---------------|
| | | ACK F10 |
| | 480 F11 |--------------->|
| |<---------------| |
| | ACK F12 | |
| 480 F13 |--------------->| |
|<---------------| | |
| ACK F14 | | |
|--------------->| | |
| | | |
In this scenario, User B initially sends a 180 Ringing response to
User A, indicating that alerting is taking place. However, then a
480 Unavailable is then sent to User A. This response is
acknowledged then proxied back to User A.
Message Details
F1 INVITE A -> Proxy 1
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Proxy-Authorization: Digest username="UserA", realm="atlanta.com",
nonce="aa9311cf5904ba7d8dc3a5ab253028fa", opaque="",
uri="sip:UserB@biloxi.com",
response="59a46a91bf1646562a4d486c84b399db"
Content-Type: application/sdp
Johnston et al Expires - April 2002 [Page 86]
SIP Basic Call Flow Examples October 2002
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
/*Client for A prepares to receive data on port 49172 from the
network.*/
F2 INVITE Proxy 1 -> Proxy 2
INVITE sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 69
Record-Route: <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F3 100 Trying Proxy 1 -> A
SIP/2.0 100 Trying
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
Johnston et al Expires - April 2002 [Page 87]
SIP Basic Call Flow Examples October 2002
F4 INVITE Proxy 2 -> B
INVITE sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Max-Forwards: 68
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserA@client.atlanta.com>
Content-Type: application/sdp
Content-Length: 143
v=0
o=UserA 2890844526 2890844526 IN IP4 client.atlanta.com
s=-
c=IN IP4 192.0.2.101
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
F5 100 Trying Proxy 2 -> Proxy 1
SIP/2.0 100 Trying
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F6 180 Ringing B -> Proxy 2
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Johnston et al Expires - April 2002 [Page 88]
SIP Basic Call Flow Examples October 2002
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F7 180 Ringing Proxy 2 -> Proxy 1
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F8 180 Ringing Proxy 1 -> A
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
Record-Route: <sip:ss2.biloxi.com;lr>, <sip:ss1.atlanta.com;lr>
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Contact: <sip:UserB@client.biloxi.com>
Content-Length: 0
F9 480 Temporarily Unavailable B -> Proxy 2
SIP/2.0 480 Temporarily Unavailable
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
;received=192.0.2.222
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Johnston et al Expires - April 2002 [Page 89]
SIP Basic Call Flow Examples October 2002
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F10 ACK Proxy 2 -> B
ACK sip:UserB@client.biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss2.biloxi.com:5060;branch=z9hG4bK721e418c4.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F11 480 Temporarily Unavailable Proxy 2 -> Proxy 1
SIP/2.0 480 Temporarily Unavailable
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
;received=192.0.2.111
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F12 ACK Proxy 1 -> Proxy 2
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP ss1.atlanta.com:5060;branch=z9hG4bK2d4790.1
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
F13 480 Temporarily Unavailable Proxy 1 -> A
Johnston et al Expires - April 2002 [Page 90]
SIP Basic Call Flow Examples October 2002
SIP/2.0 480 Temporarily Unavailable
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
;received=192.0.2.101
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 INVITE
Content-Length: 0
F14 ACK A -> Proxy 1
ACK sip:UserB@biloxi.com SIP/2.0
Via: SIP/2.0/UDP client.atlanta.com:5060;branch=z9hG4bK74bf9
Max-Forwards: 70
From: BigGuy <sip:UserA@atlanta.com>;tag=9fxced76sl
To: LittleGuy <sip:UserB@biloxi.com>;tag=314159
Call-ID: 2xTb9vxSit55XU7p8@atlanta.com
CSeq: 1 ACK
Content-Length: 0
Security Considerations
Since this document contains examples of SIP session establishment,
the security considerations in RFC 3261 [2] apply. RFC 3261
describes the basic threats including registration hijacking, server
impersonation, message body tampering, session modifying or teardown,
and denial of service and amplification attacks. The use of HTTP
Digest as shown in this document provides one-way authentication and
protection against replay attacks. TLS transport is used in
registration scenarios due to the lack of integrity protection in
HTTP Digest and the danger of registration hijacking without it, as
described in RFC 3261 [2]. A full discussion of the weaknesses of
HTTP Digest is provided in RFC 3261 [2]. The use of TLS and the
Secure SIP (sips) URI scheme provides a better level of security
including two-way authentication. IPsec can also improve security.
S/MIME can provide end-to-end confidentiality and integrity
protection of message bodies, as described in RFC 3261.
References
1 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
2 Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and Schooler, E., "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
Johnston et al Expires - April 2002 [Page 91]
SIP Basic Call Flow Examples October 2002
3 Rosenberg, J. and Schulzrinne, H., "An Offer/Answer Model with
SDP", Internet Engineering Task Force, RFC 3264, April 2002.
4 Johnston, A., Donovan, S., Sparks, R., Cunningham, C., Summers, K.,
"Session Initiation Protocol PSTN Call Flows", RFC xxxx, August
2002.
5 Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach,
P., Luotonen, A. and Stewart, L., "HTTP authentication: Basic and
Digest Access Authentication", RFC 2617, June 1999.
Acknowledgments
This document is has been a group effort by the SIP and SIPPING WGs.
The authors wish to thank everyone who has read, reviewed, commented,
or made suggestions to improve this document.
Thanks to Rohan Mahy, Adam Roach, Gonzalo Camarillo, Cullen Jennings,
and Tom Taylor for their detailed comments during the final review.
Thanks to Dean Willis for his early contributions to the development
of this document.
The authors wish to thank Neil Deason for his additions to the
Torture Test messages and Kundan Singh for performing parser
validation of messages.
The authors wish to thank the following individuals for their
participation in the review of this call flows document: Aseem
Agarwal, Rafi Assadi, Ben Campbell, Sunitha Kumar, Jon Peterson, Marc
Petit-Huguenin, Vidhi Rastogi, and Bodgey Yin Shaohua.
The authors also wish to thank the following individuals for their
assistance: Jean-Francois Mule, Hemant Agrawal, Henry Sinnreich,
David Devanatham, Joe Pizzimenti, Matt Cannon, John Hearty, the whole
MCI WorldCom IPOP Design team, Scott Orton, Greg Osterhout, Pat
Sollee, Doug Weisenberg, Danny Mistry, Steve McKinnon, and Denise
Ingram, Denise Caballero, Tom Redman, Ilya Slain, Pat Sollee, John
Truetken, and others from MCI WorldCom, 3Com, Cisco, Lucent and
Nortel.
Author's Addresses
Johnston et al Expires - April 2002 [Page 92]
SIP Basic Call Flow Examples October 2002
All listed authors actively contributed large amounts of text to this
document.
Alan Johnston
WorldCom
100 South 4th Street
St. Louis, MO 63102
USA
EMail: alan.johnston@wcom.com
Steve Donovan
dynamicsoft, Inc.
5100 Tennyson Parkway
Suite 1200
Plano, Texas 75024
USA
EMail: sdonovan@dynamicsoft.com
Robert Sparks
dynamicsoft, Inc.
5100 Tennyson Parkway
Suite 1200
Plano, Texas 75024
USA
EMail: rsparks@dynamicsoft.com
Chris Cunningham
dynamicsoft, Inc.
5100 Tennyson Parkway
Suite 1200
Plano, Texas 75024
USA
EMail: ccunningham@dynamicsoft.com
Kevin Summers
Sonus
1701 North Collins Blvd, Suite 3000
Richardson, TX 75080
USA
Email: kevin.summers@sonusnet.com
Johnston et al Expires - April 2002 [Page 93]
SIP Basic Call Flow Examples October 2002
Copyright Notice
"Copyright (C) The Internet Society 2002. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Johnston et al Expires - April 2002 [Page 94]
