draft-ietf-sip-dhcp-02.txt   draft-ietf-sip-dhcp-03.txt 
Internet Engineering Task Force SIP WG Internet Engineering Task Force SIP WG
Internet Draft G.Nair, H.Schulzrinne Internet Draft G.Nair, H.Schulzrinne
draft-ietf-sip-dhcp-02.txt Columbia University draft-ietf-sip-dhcp-03.txt Columbia University
January 15, 2001 January 20, 2001
Expires: June 2001 Expires: June 2001
DHCP Option for SIP Servers DHCP Option for SIP Servers
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress". material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
To view the list Internet-Draft Shadow Directories, see To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
Abstract Abstract
This document defines a DHCP option that contains a pointers to one This document defines a DHCP option that contains a single name that
or more SIP outbound proxy servers. This is one of the many methods can be mapped to one or more SIP outbound proxy servers. This is one
that a SIP client can use to obtain the addresses of such a local SIP of the many methods that a SIP client can use to obtain the addresses
server. of such a local SIP server.
1 Terminology 1 Terminology
DHCP client: A DHCP [1] client is an Internet host that uses DHCP client: A DHCP [1] client is an Internet host that uses
DHCP to obtain configuration parameters such as a network DHCP to obtain configuration parameters such as a network
address. address.
DHCP server: A DHCP server is an Internet host that returns DHCP server: A DHCP server is an Internet host that returns
configuration parameters to DHCP clients. configuration parameters to DHCP clients.
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outbound proxy server, as defined in [3]. In the context of outbound proxy server, as defined in [3]. In the context of
this document, a SIP server refers to the host the SIP this document, a SIP server refers to the host the SIP
server is running on. server is running on.
SIP client: As defined in RFC 2543. The client can be a user SIP client: As defined in RFC 2543. The client can be a user
agent client or the client portion of a proxy server. In agent client or the client portion of a proxy server. In
the context of this document, a SIP client refers to the the context of this document, a SIP client refers to the
host the SIP client is running on. host the SIP client is running on.
In this document, the key words "MUST", "MUSTNOT", "REQUIRED", In this document, the key words "MUST", "MUSTNOT", "REQUIRED",
"SHALL", "SHALLNOT", "SHOULD", "SHOULDNOT", "RECOMMENDED", "MAY", and "SHALL", "SHALLNOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
"OPTIONAL" are to be interpreted as described in RFC 2119 [4]. and "OPTIONAL" are to be interpreted as described in RFC 2119 [4].
2 Introduction 2 Introduction
The Session Initiation Protocol (SIP) [2] is an application-layer The Session Initiation Protocol (SIP) [2] is an application-layer
control protocol that can establish, modify and terminate multimedia control protocol that can establish, modify and terminate multimedia
sessions or calls. A SIP system has a number of logical components: sessions or calls. A SIP system has a number of logical components:
user agents, proxy servers, redirect servers and registrars. User user agents, proxy servers, redirect servers and registrars. User
agents MAY contain SIP clients, proxy servers always do. agents MAY contain SIP clients, proxy servers always do.
This draft specifies a DHCP option [1,5] that allows SIP clients to This draft specifies a DHCP option [1,5] that allows SIP clients to
locate a local SIP server that is to be used for all outbound SIP locate a local SIP server that is to be used for all outbound SIP
requests, a so-called outbound proxy server. (SIP clients MAY contact requests, a so-called outbound proxy server. (SIP clients MAY contact
the address identified in the SIP URL directly, without involving a the address identified in the SIP URL directly, without involving a
local SIP server. However in some circumstances, when firewalls are local SIP server. However in some circumstances, when firewalls are
present, SIP clients need to use a local server for outbound present, SIP clients need to use a local server for outbound
requests.) This is one of many possible solutions for locating the requests.) This is one of many possible solutions for locating the
outbound SIP server; manual configuration is an example of another. outbound SIP server; manual configuration is an example of another.
3 Overview 3 SIP server DHCP options
The SIP client obtains a DNS [6] string via a DHCP option. This The SIP client obtains a DNS [6] full-qualified domain name (FQDN)
string is then used by the mechanism described in [3] to locate the via a DHCP option. This FQDN is then used by the mechanism described
outbound proxy server. In summary, the domain name encoded in the in [3] to locate the outbound proxy server. In summary, the domain
string is used first in a DNS SRV lookup and, if that fails because name encoded in the string is used first in a DNS SRV lookup and, if
of a lack of matching DNS SRV records, in an address record lookup. that fails because of a lack of matching DNS SRV records, in an
Normative details are contained in [3]. address record lookup. Normative details are contained in [3].
4 SIP server DHCP options It is possible, but NOT RECOMMENDED that the string is the textual
representation of a network address, e.g., a "dotted quad" for IPv4
and the hexadecimal representation of RFC 2373 [7].
This option specifies the DNS [6] string that is passed to the The code for this option is TBD. The length of the DNS name string is
client. This string SHOULD be the domain name of the SIP server
(rather than a textual representation of the network address). The
code for this option is TBD. The length of the DNS name string is
specified in `Len'. The maximum length of this string is 255 octets specified in `Len'. The maximum length of this string is 255 octets
and minimum length is 1 octet. For example, a value may be and minimum length is 1 octet. For example, a value may be
"sip.example.com". "sip.example.com".
Code Len DNS name of SIP server Code Len DNS name of SIP server
+-----+-----+-----+-----+-----+-----+-----+-- +-----+-----+-----+-----+-----+-----+-----+--
| TBD | n | s1 | s2 | s3 | s4 | s5 | ... | TBD | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+-- +-----+-----+-----+-----+-----+-----+-----+--
5 Security Consideration 4 Security Consideration
There are no security considerations beyond those described in RFC There are no security considerations beyond those described in RFC
2132. 2132, RFC 2543 [2] and RFC XXX [3].
5 IANA Considerations
IANA has assigned a DHCP option number of TBD for the "SIP Servers
DHCP Option" defined in this document.
6 Acknowledgements 6 Acknowledgements
Robert Elz, Wenyu Jiang, Peter Koch, Erik Nordmark, Jonathan Robert Elz, Wenyu Jiang, Peter Koch, Thomas Narten, Erik Nordmark,
Rosenberg, Kundan Singh, Sven Ubik and Bernie Volz provided useful Jonathan Rosenberg, Kundan Singh, Sven Ubik and Bernie Volz provided
feedback. useful feedback.
7 Authors' Addresses 7 Authors' Addresses
Gautam Nair Gautam Nair
Dept. of Computer Science Dept. of Computer Science
Columbia University 1214 Amsterdam Avenue, MC 0401 Columbia University 1214 Amsterdam Avenue, MC 0401
New York, NY 10027 New York, NY 10027
USA USA
electronic mail: gnair@cs.columbia.edu electronic mail: gnair@cs.columbia.edu
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levels," Request for Comments 2119, Internet Engineering Task Force, levels," Request for Comments 2119, Internet Engineering Task Force,
Mar. 1997. Mar. 1997.
[5] S. Alexander and R. Droms, "DHCP options and BOOTP vendor [5] S. Alexander and R. Droms, "DHCP options and BOOTP vendor
extensions," Request for Comments 2132, Internet Engineering Task extensions," Request for Comments 2132, Internet Engineering Task
Force, Mar. 1997. Force, Mar. 1997.
[6] P. V. Mockapetris, "Domain names - implementation and [6] P. V. Mockapetris, "Domain names - implementation and
specification," Request for Comments 1035, Internet Engineering Task specification," Request for Comments 1035, Internet Engineering Task
Force, Nov. 1987. Force, Nov. 1987.
[7] R. Hinden and S. Deering, "IP version 6 addressing architecture,"
Request for Comments 2373, Internet Engineering Task Force, July
1998.
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