Internet Engineering Task Force P. Dawes
Internet-Draft Vodafone Group
Intended status: Standards Track October 18, 2013
Expires: April 21, 2014
Requirements for Marking SIP Messages to be Logged
draft-dawes-dispatch-logme-reqs-03
Abstract
SIP networks use signalling monitoring tools to diagnose user
reported problem and for regression testing if network or client
software is upgraded. As networks grow and become interconnected,
including connection via transit networks, it becomes impractical to
predict the path that SIP signalling will take between clients, and
therefore impractical to monitor SIP signalling end-to-end.
This draft describes requirements for adding an indicator to the SIP
protocol which can be used to mark signalling as of interest to
logging. Such marking will typically be applied as part of network
testing controlled by the network operator and not used in regular
client signalling. However, such marking can be carried end-to-end
including the SIP terminals, even if a session originates and
terminates in different networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2014.
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Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Motivating Scenario . . . . . . . . . . . . . . . . . . . . . 3
4. Skeleton Diagnostic Procedure . . . . . . . . . . . . . . . . 4
5. Requirements for a Log Me Marker . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6.1. Trust Domain . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Security Threats . . . . . . . . . . . . . . . . . . . . 6
6.2.1. Log-me marking . . . . . . . . . . . . . . . . . . . 6
6.2.2. Debug server address . . . . . . . . . . . . . . . . 7
6.2.3. Sending logged information . . . . . . . . . . . . . 7
7. Potential Solutions . . . . . . . . . . . . . . . . . . . . . 7
7.1. Functionality Common to all Solutions . . . . . . . . . . 7
7.1.1. Starting and Stopping log-me marking . . . . . . . . 7
7.1.1.1. General . . . . . . . . . . . . . . . . . . . . . 7
7.1.1.2. Configuration for log-me marking . . . . . . . . 7
7.1.1.3. Maintaining State . . . . . . . . . . . . . . . . 8
7.1.2. Sending logs to a debug server . . . . . . . . . . . 10
7.1.2.1. Server address . . . . . . . . . . . . . . . . . 10
7.1.2.2. Protecting logs . . . . . . . . . . . . . . . . . 10
7.2. Solution A: LogMe header field . . . . . . . . . . . . . 10
7.2.1. Introduction . . . . . . . . . . . . . . . . . . . . 10
7.2.2. Server Procedures . . . . . . . . . . . . . . . . . . 10
7.2.2.1. General . . . . . . . . . . . . . . . . . . . . . 10
7.2.2.2. Sending logged information to a debug server . . 10
7.2.3. Client Procedures . . . . . . . . . . . . . . . . . . 10
7.2.3.1. General . . . . . . . . . . . . . . . . . . . . . 11
7.2.4. Identifying test cases . . . . . . . . . . . . . . . 11
7.2.5. Collecting logged information at a debug server . . . 11
7.2.6. Examples . . . . . . . . . . . . . . . . . . . . . . 11
7.3. Solution B: New Value for purpose header field parameter
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in Call-Info: . . . . . . . . . . . . . . . . . . . . . . 12
7.4. Solution C: New 'debug' header field parameter to be used
in Session-ID header field . . . . . . . . . . . . . . . 13
7.5. Comparison of Potential Solutions . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
If users experience problems with setting up sessions using SIP,
their service provider needs to find out why by examining the SIP
signalling. Also, if network or client software or hardware is
upgraded regression testing is needed. Such diagnostics apply to a
small proportion of network traffic and can apply end-to-end, even if
signalling crosses several networks possibly belonging to several
different network operators. It may not be possible to predict the
path through those networks in advance, therefore a mechanism is
needed to mark a session as being of interest to enable SIP entities
along the signalling path to provide diagnostic logging. This draft
describes the requirements for such a 'log me' marker for SIP
signalling.
2. Requirements Language
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 [RFC2119].
3. Motivating Scenario
Signalling for SIP session setup can cross several networks, and
these networks may not have common ownership and also may be in
differrent countries. If a single operator wishes to perform
regression testing or fault diagnosis end-to-end, the separate
ownership of networks that carry the signalling and the explosion in
the number of possible signalling paths through SIP entities from the
originating to the terminating user make it impractical to pre-
configure logging of an end-to-end SIP signalling of a session of
interest.
The figure below shows an example of a signalling path through
multiple networks.
+------------------+ +------------------+
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| COUNTRY A | | COUNTRY B |
| Operator A | | Operator A |
| | | |
| SIP Phones | | SIP Phones |
| | //| |
+------------------+ // +------------------+
| //
| //
,'```', // +------------------+
.`',.' `..'``',<==// | COUNTRY B |
,' Operator A `', | Operator A |
; Backbone Network ..'-------| |
', ,., .'` | PSTN phones |
'.,.`'.,,,.` `''` | |
|| +------------------+
||
\/
+------------------+
| |
| Transit Network |
| |
| |\\
+------------------+ \\
| \\
| \\
+------------------+ \\ +------------------+
| COUNTRY D | \\ | COUNTRY C |
| Operator C | \\=>| Operator B |
| | | |
| SIP Phones | | SIP Phones |
| | | |
+------------------+ +------------------+
Figure 1: Example signalling path through multiple networks
4. Skeleton Diagnostic Procedure
The skeleton diagnostic procedure is as follows:
o The user's terminal is placed in debug mode. The terminal logs
its own signalling and inserts a log me marker into SIP requests
for session setup
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o All SIP entities that the signalling traverses, from the first
proxy the terminal connects to at the edge of the network to the
destination client terminal, can detect that the log me marker is
present and can log SIP requests and responses that contain the
marker if configured to do so.
o Subsequent responses and requests in the same dialog are logged.
o Logging stops, either because the dialog has ended or because a
'stop event', typically expiry of a certain amount of time,
occurred
o The user's terminal and any other SIP entity that has logged
signalling sends logs to a server that is co-ordinating
diagnostics.
5. Requirements for a Log Me Marker
o REQ1: It shall be possible to mark a SIP request or response as of
interest for logging by inserting a log me marker. This is known
as log-me marking.
o REQ2: It shall be possible for a log-me marker to cross network
boundaries.
o REQ3: A log-me marker is most effective if it passes end-to-end.
However, source networks should behave responsibly and not leave
it to a downstream network to detect and remove a marker that it
will not use. A log-me marker should be removed at trust domain
boundaries.
o REQ4: SIP entities should log SIP requests or responses with a
log-me marker.
o REQ5: If a UA receives a request with a log-me marker, it shall
echo that log-me marker in responses to that request.
o REQ6: A SIP proxy may perform log-me marking of requests and
responses. Typical cases where a proxy needs to perform log-me
marking are when a UA has not marked a request and when responses
received on a dialog of interest for logging do not contain a log-
me marker. In these cases, the entity that performs log-me
marking is stateful inasmuch as it must remember when a dialog is
of interest for logging.
o REQ7: For SIP proxies, logging of SIP requests that contain a log-
me marker may be stateless. For example, it is not required for a
SIP entity to maintain state of which SIP requests contained a
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log-me marker in order to log responses to those requests.
Echoing a log-me marker in responses is the responsibility of the
UA that receives a request.
o REQ8: A log-me marker may include an identifier that indicates the
test case that caused it to be inserted, known as a test case
identifier. The test case identifier does not have any impact on
session setup, it is used by the diagnostic server to collate all
logged SIP requests and responses to the initial SIP request in a
dialog or standalone transaction. The Session-ID described in I-D
.ietf-insipid-session-id-reqts [I-D.ietf-insipid-session-id-reqts]
could be used as the test case identifier but it would be useful
for the UA to log a human readable name together with this
Session-ID when it performs log me marking of an initial SIP
request.
o REQ9: A log-me marker may include a locator of the server that
collects logs. This locator is known as the diagnostic server
identifier and may be an address of a server. A SIP entity can
use the diagnostic server identifier to send collected logs to the
diagnostic server.
6. Security Considerations
All drafts are required to have a security considerations section.
See RFC 3552 [RFC3552] for a guide.
6.1. Trust Domain
Since a log me marker may cause a SIP entity to log the SIP header
and body of a request or response, the log me marker should be
removed at a trust domain boundary. If a prior agreement to log
sessions exists with the net hop network then the log me marker might
not be removed.
6.2. Security Threats
6.2.1. Log-me marking
The log me marker is not sensitive information, although it will
sometimes be inserted because a particular device is experiencing
problems.
The presence of a log me marker will cause some SIP entities to log
signalling. Therefore, this marker must be removed at the earliest
opportunity if it has been incorrectly inserted.
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Activating a debug mode affects the operation of a terminal,
therefore it must be supplied by an authorized server to an
authorized terminal, it must not be altered in transit, and it must
not be readable by an unauthorized third party.
Logged signalling is privacy-sensitive data, therefore it must be
passed to an authorized server, it must not be altered in transit,
and it must not be readable by an unauthorized third party.
6.2.2. Debug server address
Log me marking may include the address of a debug server in the form
of a URL. In order to prevent sending of logs to an unauthorised
server a SIP entity that supports logging should authenticate the
debug server, for example by referring to a statically configured
white list of allowed destination domains.
6.2.3. Sending logged information
A SIP entity that has logged information should encrypt it, such that
it can be decrypted only by the debug server, before sending it to a
debug server in order to protect the content of logs from a third
party.
7. Potential Solutions
This section describes potential solutions to the logme requirements
and functionality that is common to all solutions.
7.1. Functionality Common to all Solutions
7.1.1. Starting and Stopping log-me marking
7.1.1.1. General
A server or client needs to determine when to perform log-me marking.
A client or server determines whether to perform log-me marking only
by configuration. A regression test might be configured to log-me
mark all SIP requests for a given time period whereas a
troubleshooting test might be configured to mark sessions based on
criteria specific to a reported fault. When configuration has caused
a client or server to start log-me marking requests and responses in
a dialog, marking continues until the dialog ends or until
configuration indicates that marking must stop earlier, for example
after certain time period has elapsed.
7.1.1.2. Configuration for log-me marking
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Configuration of a client or server to perform log-me marking can be
done in any way that is convenient to the configured entity. For
example, an XML file might be used to list conditions for starting
and stopping based on time.
09:00:00
09:10:00
Figure 2: Simple example log-me configuration
7.1.1.3. Maintaining State
An entity that inserts a log-me marker in a SIP request should ensure
that a log-me marker is also inserted in responses to that request.
An entity that receives a SIP reqeust with a log-me marker may also
ensure that responses to that requset contain a log-me marker by
inserting one if it is missing. Entities that perform this log-me
marking or checking must maintain a record of which dialogs are of
interest to logging.
In the figure below, the edge proxy in the originating network
maintains state to ensure log-me marking of SIP requests and in the
terminating network the registrar maintains state to ensure log-me
marking of SIP responses. Such behaviour is useful to for logging if
end devices do not insert or echo a log-me marker.
Alice Proxy Registrar
u1.foocorp.com p1.foocorp.com r1.foocorp.com
| | |
|(1) INVITE | |
| (u1 does not insert log-me marker in SIP request)
|----------------->| |
| |(2) INVITE |
| | Logme: |
| | (p1 inserts log-me marker. p1 maintains
| | state and inserts log-me marker in all
| | requests on this dialog)
| |----------------->|
| | |(3) INVITE
| | | LogMe:
| | |--------> (to barcorp)
| | |
| | |
| | |
| | |(8) 200 OK
| | | Logme:
| |(9) 200 OK |<-------- (from barcorp)
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| | LogMe: |
| |<-----------------|
|(10) 200 OK | |
| LogMe: | |
|<-----------------| |
| | |
|(11) ACK | |
|--------------------------------------------------------->
| | |
Proxy Registrar Bob
p1.barcorp.com r1.barcorp.com u1.barcorp.com
| | |
(3) INVITE | |
Logme: | |
----->|(from foocorp) | |
| | |
|(4) INVITE | |
| Logme: | |
|----------------->| |
| |(5) INVITE |
| Logme: |
| |----------------->|
| | |
| |(6) 200 OK |
| | (u1 does not echo LogMe:
| | to SIP response)|
| |<-----------------|
|(7) 200 OK | |
|LogMe: | |
| (r1 inserts log-me marker. r1 maintains
| state and inserts log-me marker in all
| responses on this dialog)
|<-----------------| |
| | |
(8) 200 OK | |
LogMe: | |
<----| | |
| | |
(11) ACK | |
from foocorp) -------------------------->|
| | |
Figure 3: Maintaining state for log-me marking
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7.1.2. Sending logs to a debug server
7.1.2.1. Server address
Log me marking may include the address of a debug server in the form
of a URL. In order to prevent sending of logs to an unauthorised
server a SIP entity that supports logging should authenticate the
debug server, for example by referring to a statically configured
white list of allowed destination domains.
7.1.2.2. Protecting logs
A SIP entity that has logged information should encrypt it, such that
it can be decrypted only by the debug server, before sending in order
to protect the content of logs from a third party.
7.2. Solution A: LogMe header field
7.2.1. Introduction
A new SIP header field, e.g. 'LogMe:', is defined to indicate that a
session is of interest to logging. A supporting UA inserts the LogMe
header field in an initial SIP request, and subsequent SIP requests
belonging to the same dialog if any, and echoed in responses by a
supporting UA that receives the SIP request. The LogMe header field
has two header field parameters defined, one free-text name of the
test case being performed, and one address of a server where
collected logging will be sent after logging has terminated.
7.2.2. Server Procedures
7.2.2.1. General
A server may insert a logme marker, start logging, and stop logging.
A server may perform log-me marking. Typically, server marking is
useful if a session is of interest to logging and the client did not
perform log-me marking. If a server inserts a log-me marker, that
server must maintain state in order to echo a log-me marker in SIP
responses in a session of interest to logging.
7.2.2.2. Sending logged information to a debug server
A server may send logged information to a debug server when a dialog
has ended.
7.2.3. Client Procedures
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7.2.3.1. General
A client may perform any of the server procedures and may echo a log
me marker from a request to a response.
7.2.4. Identifying test cases
The Session-ID header field may be used to identify test cases such
as particular regression tests.
7.2.5. Collecting logged information at a debug server
Clients and servers may send logged information to a debug server.
7.2.6. Examples
Alice Proxy Registrar Debug Server
u1.foocorp.com p1.foocorp.com r1.foocorp.com d1.foocorp.com
| | | |
|(1) INVITE | | |
| LogMe: testCaseName="test01"; debugServer="d1.foocorp.com"
|----------------->| | |
| |(2) INVITE | |
| | Logme: | |
| |----------------->| |
| | |(3) INVITE |
| | | LogMe: |
| | |--------> (to barcorp)
| | | |
| | | |
| | | |
| | |(8) 200 OK
| |(9) 200 OK |<-------- (from barcorp)
| | LogMe: | |
| |<-----------------| |
|(10) 200 OK | | |
| LogMe: | | |
|<-----------------| | |
| | | |
|(11) ACK | | |
|--------------------------------------------------------->
| | | |
Proxy Registrar Bob Debug Server
p1.barcorp.com r1.barcorp.com u1.barcorp.com d1.barcorp.com
| | | |
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(3) INVITE | | |
Logme: | | |
----->|(from foocorp) |
| | | |
|(4) INVITE | | |
| Logme: | |
|----------------->| | |
| |(5) INVITE | (u1 copies LogMe: to
| Logme: | SIP response) |
| |----------------->| |
| | | |
| |(6) 200 OK | |
| | LogMe: | |
| |<-----------------| |
|(7) 200 OK | | |
|LogMe: | | |
|<-----------------| | |
| | | |
(8) 200 OK | | |
LogMe: | | |
<----| | | |
| | | |
(11) ACK | | |
(from foocorp) -------------------------->| |
| | | |
Figure 4: Signalling example for the LogMe header field solution
7.3. Solution B: New Value for purpose header field parameter in Call-
Info:
A new value is defined for the purpose header field parameter used in
Call-Info header field.
The Call-Info: header field is defined in clause 20.9 of RFC 3261
[RFC3261].
Alice Proxy Registrar Debug Server
u1.foocorp.com p1.foocorp.com r1.foocorp.com d1.foocorp.com
| | | |
|(1) INVITE | | |
| Call-Info: mailto:"SIP logging"; purpose="debug"
|----------------->| | |
| | | |
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Figure 5: Signalling example for the Call-Info: purpose parameter
solution
The Call-Info: header field can be included in methods INVITE,
OPTIONS, REGISTER (Table 2: Summary of header fields, A--O in RFC
3261 [RFC3261] clause 20.1), INFO (RFC 6086 [RFC6086]), MESSAGE (RFC
3428 [RFC3428]), PUBLISH (RFC 3903 [RFC3903]), and UPDATE (RFC 3311
[RFC3311]), and in responses to those methods. Call-Info: header
field cannot be included in methods NOTIFY, SUBSCRIBE, PRACK, or
REFER.
The Call-Info: header field has no protocol element that can be used
to indicate the test case name, therefore in this solution the test
case is identified by the Session-ID header field.
7.4. Solution C: New 'debug' header field parameter to be used in
Session-ID header field
A new header field parameter called debug is defined to be used with
the Session-ID header field (described in I-D.ietf-insipid-session-
id-reqts [I-D.ietf-insipid-session-id-reqts]).
Alice Proxy Registrar Debug Server
u1.foocorp.com p1.foocorp.com r1.foocorp.com d1.foocorp.com
| | | |
|(1) INVITE | | |
| Session-ID: debug="testCaseName" |
|----------------->| | |
| | | |
Figure 6: Signalling example for the Session-ID: header field
parameter solution
7.5. Comparison of Potential Solutions
The table below summarizes the features of each potential solution.
Other solutions are not excluded.
+----+--------------+-----------------------------------------------+
| | Solution | Summary |
+----+--------------+-----------------------------------------------+
| A | Log-Me: | Specify a new SIP header field. Could be |
| | header field | included in all SIP requests and responses. |
| | | All behaviour including proxy handling in |
| | | terms of add, delete, modify, and read, and |
| | | which requests may or may not include the |
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| | | header field must be defined. |
| | | |
| B | New value | Rules for including, reading, modifying etc. |
| | for the | are already defined by Call-Info. Call-Info |
| | purpose | cannot be inserted in all requests and |
| | parameter of | responses, but can be included for the SIP |
| | the Call- | methods of most interest to debugging and |
| | Info header | regression testing. No element to hold a test |
| | field e.g. | case name so test case is identified by the |
| | "debug" | Session-ID header field. |
| | | |
| C | New header | Might be viewed as a reason to remove the |
| | field | Session-ID header field, which would violate |
| | parameter | the Session-ID requirement: "REQ3: The |
| | for Session- | solution must require that the identifier, if |
| | ID header | present, pass unchanged through SIP B2BUAs or |
| | field e.g. | other intermediaries." in I-D.ietf-insipid- |
| | debug | session-id-reqts [I-D.ietf-insipid-session- |
| | | id-reqts] |
+----+--------------+-----------------------------------------------+
Table 1: Summary comparison of potential solutions
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[I-D.ietf-insipid-session-id-reqts]
Jones, P., Salgueiro, G., Polk, J., Liess, L., and H.
Kaplan, "Requirements for an End-to-End Session
Identification in IP-Based Multimedia Communication
Networks", draft-ietf-insipid-session-id-reqts-07 (work in
progress), June 2013.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
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[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3311] Rosenberg, J., "The Session Initiation Protocol (SIP)
UPDATE Method", RFC 3311, October 2002.
[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
and D. Gurle, "Session Initiation Protocol (SIP) Extension
for Instant Messaging", RFC 3428, December 2002.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
[RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension
for Event State Publication", RFC 3903, October 2004.
[RFC6086] Holmberg, C., Burger, E., and H. Kaplan, "Session
Initiation Protocol (SIP) INFO Method and Package
Framework", RFC 6086, January 2011.
Appendix A. Additional Stuff
This becomes an Appendix.
Author's Address
Peter Dawes
Vodafone Group
The Connection
Newbury, Berkshire RG14 2FN
UK
Phone: +44 7717 275009
Email: peter.dawes@vodafone.com