Internet DRAFT - draft-brunner-sipping-sipautoconf

draft-brunner-sipping-sipautoconf






Sipping Working Group                                         M. Brunner
Internet-Draft                                            M. Stiemerling
Expires: April 17, 2006                                     S. Niccolini
                                                                     NEC
                                                        October 14, 2005


    Requirements and Framework for SIP User Agent Auto-Configuration
                  draft-brunner-sipping-sipautoconf-00

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   The problem of today's VoIP user agents (hardware terminals, SIP soft
   phones) is the need for quite a bit of manual configuration at the
   initialization time as well as when moving from one environment to
   another.  The information to be configured is typically not known by
   the end-user.  Automatic configuration of SIP user agents would
   release the user of these configuration tasks.  This memo describes
   the challenges of auto-configuration of SIP user agents and gives



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   some requirements for further discussions.

Table of Contents

   1.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  3

   2.  Assumptions  . . . . . . . . . . . . . . . . . . . . . . . . .  3

   3.  Overview of the existing Solutions . . . . . . . . . . . . . .  3
     3.1   DHCP Options . . . . . . . . . . . . . . . . . . . . . . .  3
     3.2   Download configuration-file using FTP/TFTP/WebDAV  . . . .  3

   4.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  4
     4.1   Minimal Manual Intervention  . . . . . . . . . . . . . . .  4
     4.2   Works in different Environments with different Network
           Attachment Points  . . . . . . . . . . . . . . . . . . . .  4
     4.3   Based on the SIP protocol  . . . . . . . . . . . . . . . .  4
     4.4   Support of SIP and non-SIP configurations  . . . . . . . .  4

   5.  Framework  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     5.1   Possibilities for Extending SIP  . . . . . . . . . . . . .  5
     5.2   Configuration Information  . . . . . . . . . . . . . . . .  5

   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5

   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     7.1   Normative References . . . . . . . . . . . . . . . . . . .  6
     7.2   Informative References . . . . . . . . . . . . . . . . . .  6

       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  6

       Intellectual Property and Copyright Statements . . . . . . . .  8



















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1.  Problem Statement

   The problem of today's VoIP user agents (hardware terminals, SIP soft
   phones) is the need for quite a bit of manual configuration at the
   initialization time as well as when moving from one environment to
   another.  The information to be configured is typically not known by
   the end-user.  Additionally, the information might depend on the
   location of the terminal in the network (so the environment might
   have changed, NATs, Firewalls, access speed, ...).  Finally, also
   service specific configurations typically require a certain degree of
   configuration (e.g., the presence server location, etc.).  Currently,
   users are forced to enter this type of information manually into the
   SIP phones, which is a cumbersome and error prone task.  Users need
   to edit configuration files or enter the configuration data into a
   Graphical User Interface in the better case.  However, a full
   configuration set for SIP phones is likely to not be easily handled
   by an everyday average user and automatic configuration of these user
   agents is needed.

2.  Assumptions

   1.  We assume that the IP configuration (e.g., IP address, netmask,
       default router, etc) has happened beforehand, for example,
       through DHCP or IPv6 auto-configuration.
   2.  Additionally, we assume that the SIP proxy to be used by that
       user agent (home SIP proxy) can be found through DNS given the
       SIP URI of the user, or received via DHCP as well.

3.   Overview of the existing Solutions

3.1  DHCP Options

   The has been standards for using DHCP options for automatically
   configure the local SIP proxy [RFC3361] [RFC3319] the mechanisms can
   be used for other configurations.  However, only the local
   configuration is possible to get through that mechanism.  So in case
   of different network attachment of the same terminal the mechanism
   does not really work.

3.2  Download configuration-file using FTP/TFTP/WebDAV

   Various product use different types of means to download a SIP client
   configuration file from a server using FTP, TFTP, or WebDAV or other
   means for getting a file.  However, this requires an additional peace
   of software to be installed on the user agent's device.






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4.  Requirements

4.1  Minimal Manual Intervention

   Any user configuring a SIP client must only enter his SIP URI and
   potentially some security relevant material such as a password.
   Everything else must be done automatically.

4.2  Works in different Environments with different Network Attachment
     Points

   Since SIP terminals are getting mobile, the SIP client must
   potentially get re-configured when attached to a network at a
   different location.  Or when the configuration of the network, in
   which the terminal currently is located, changes due to a change in
   configuration, the SIP client must be re-configured automatically.

4.3  Based on the SIP protocol

   The benefit of using SIP is that it easily integrates with the
   required SIP stack already available on the client.  No other
   protocols are required.

4.4  Support of SIP and non-SIP configurations

   It should be possible to configure SIP related information as well as
   non-SIP related information at the user agent through the auto-
   configuration mechanism.  Non-SIP configuration refers to further
   information used in the process of getting a SIP session up and
   running.  For instance, configurations required for proper operation
   of VoIP, such as STUN server, etc. (see a preliminary list of such
   information below)

5.  Framework

   We need to differentiate two base cases, the initial configuration
   per user and constant refinement and re-checking of the
   configuration.  The initial configuration is performed when the user
   agent is plugged and/or switched on the very first time and when a
   user utilizes a particular user agent the first time.  In all this
   cases the user has still to enter his SIP URI and authentication
   material.  In the phase of constant refinement the configuration
   needs to change because the SIP proxy or other SIP infrastructure
   devices have changed, or because the environment of the phone has
   changed.  Environment changes mainly apply to all NAT/FW issues and
   to the potential requirements of using the local SIP proxy for the
   SIP communication.




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   Extending the Session Initiation Protocol (SIP) protocol [RFC3261] to
   automatically configure SIP user agents in fixed as well as in
   dynamic environments has benefits.  The SIP message exchanges between
   SIP user agents and SIP proxies are used to provide the means of
   setting configuration information to the SIP user agent.  This
   typically happens in one of the first SIP protocol exchanges between
   the SIP proxy and the SIP user agent.

5.1  Possibilities for Extending SIP

   Typically the first exchange is the SIP REGISTER message and its
   reply from the SIP proxy (typically, but not limited to, a "401
   UNAUTHORIZED" or "200 OK").  So this first SIP exchange can be used
   for getting configurations from the SIP proxy to the SIP user agent.

   Another possibility is the definition of a separate new message
   exchange for the auto-configuration purpose only.  This has the
   benefit of separating concerns.

   Finally, also the event mechanisms [RFC3265] could be used.
   Basically subscribe for configuration events and than receiving
   events containing the configuration information.

5.2  Configuration Information

   Several configuration information relating to the SIP communication
   should be transferred to the user agent including the following.

   1.  A list of other candidate SIP proxies.
   2.  The first and primary configuration information are SIP proxy
       capabilities including the list and preferred transport protocols
       available, and the list and preferred SIP proxy port numbers.
   3.  SIP stack settings (listen ports (SIP/RTP), timeout
       configurations.)
   4.  Configuration information for SIP services including Presence
       server location, push-to-talk (P2T) server, conference server,
       ...
   5.  if the network where the home SIP proxy is located is maintaining
       a STUN server or known of one, the location of one or several
       STUN servers will be configured, and also other STUN settings for
       stack/client/server are part of the configuration information.
   6.  if the network where the home SIP proxy is located is maintaining
       one or more Data (RTP) relay servers, the server location (e.g.
       TURN server) is sent to the SIP user agent.

6.  Security Considerations

   There are security issues with configuring devices, and they need be



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   be tackled reasonably.

7.  References

7.1  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [RFC3265]  Roach, A., "Session Initiation Protocol (SIP)-Specific
              Event Notification", RFC 3265, June 2002.

7.2  Informative References

   [RFC3319]  Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
              Protocol (DHCPv6) Options for Session Initiation Protocol
              (SIP) Servers", RFC 3319, July 2003.

   [RFC3361]  Schulzrinne, H., "Dynamic Host Configuration Protocol
              (DHCP-for-IPv4) Option for Session Initiation Protocol
              (SIP) Servers", RFC 3361, August 2002.


Authors' Addresses

   Marcus Brunner
   NEC
   Kurfuersten-Anlage 36
   Heidelberg,   D-69115
   Germany

   Phone: +49 6221 905 11 29
   Fax:   +49 6221 905 11 55
   Email: brunner@netlab.nec.de












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   Martin Stiemerling
   NEC
   Kurfuersten-Anlage 36
   Heidelberg,   D-69115
   Germany

   Phone: +49 6221 905 11 13
   Fax:   +49 6221 905 11 55
   Email: stiemerling@netlab.nec.de


   Saverio Niccolini
   NEC
   Kurfuersten-Anlage 36
   Heidelberg,   D-69115
   Germany

   Phone: +49 6221 905 11 18
   Fax:   +49 6221 905 11 55
   Email: saverio.niccolini@netlab.nec.de































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