Internet DRAFT - draft-pskim-sip-mipv6
draft-pskim-sip-mipv6
Network Working Group P. Kim
Internet-Draft Korea Polytechnic University
Expires: December 31, 2005 June 29, 2005
A New Mechanism for SIP over Mobile IPv6
draft-pskim-sip-mipv6-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This draft proposes a new mechanism for Session Initiation Protocol
(SIP) over Mobile IPv6. In this mechanism, a home agent (HA) on home
subnet acts as a redirect server and a registrar for SIP as well as
a home router for Mobile IPv6. Thus, a binding cache in the HA
contains location information for SIP as well as home registration
entries for Mobile IPv6. An access router on foreign subnet acts as
only a router that offers a domain name. To implement the proposed
mechanism, some messages used in network layer are newly defined,
such as a router advertisement, a router solicitation and a binding
update. In the proposed mechanism, a mobile node doesn't require
dynamic host configuration protocol (DHCP) and thus both home and
foreign subnets don't need DHCP servers, unlike existing mechanisms
on Mobile IPv4.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Network Architecture for Proposed Mechanism . . . . . . . . . 3
4. New Messages for Proposed Mechanism. . . . . . . . . . . . . . 4
4.1 New Router Advertisement Message . . . . . . . . . . . . . . 4
4.2 New Router Advertisement Message . . . . . . . . . . . . . . 5
4.3 New Binding Update Message . . . . . . . . . . . . . . . . . 5
5. Basic Operation Procedure of Proposed Mechanism . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
1. Introduction
Over the past few years, an important trend is the emergence of voice
over IP (VoIP) services and its rapid growth. For VoIP services, the
Session Initiation Protocol (SIP) has been standardized by IETF
[RFC3261]. SIP is an application layer protocol used for establishing
and tearing down multimedia sessions.Meanwhile, mobility support is
also becoming important because of the recent blossoming of mobile
appliances, such as mobile phone, handheld PC, laptop computer, and
the high desire to have seamless network connectivity. To support
mobility for IPv4, Mobile IPv4 [RFC2002] was designed by IETF. In
addition, in recent, to solve the address exhaustion problem and the
routing optimization problem with Mobile IPv4, Mobile IPv6 has been
standardized by IETF [RFC3775] for IPv6 [RFC2461].
Even though the original SIP and its applications did not consider
the mobility of the end nodes, there have been ongoing research
efforts to support mobility in the current SIP [Moh1999],
[Seol2002], [Kwon2002]. These works have been researched on Mobile
IPv4 because Mobile IPv6 was not well established until recent. To
authors' knowledge, there seems to be no well established result for
SIP over Mobile IPv6. However, as mentioned before, there are the
address exhaustion problem and the routing optimization problem in
Mobile IPv4. Therefore, mechanisms for SIP over Mobile IPv6 might be
required for wireless and mobile communication environments.
In this draft, a new mechanism for SIP over Mobile IPv6 is proposed.
In this mechanism, a home agent (HA) on home subnet acts as a
redirect server and a registrar for SIP as well as a home router for
Mobile IPv6. That is, the HA provides its inherent functions of
Mobile IPv6, such as a router advertisement and a home registration
for a mobile node (MN). In addition, for SIP, the HA accepts a
location registration request of the MN, places the information it
receives in this request into a location database, and returns the
location information of the MN to a correspondent node (CN). Thus, a
binding cache in the HA contains location information for SIP as well
as home registration entries for Mobile IPv6. On the other side, an
access router on foreign subnet, which will be called a foreign
router (FR) hereafter, provides only a router advertisement for the
MN.
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To implement the proposed mechanism, in this draft, some new messages
used in network layer are defined by adding some fields to existing
messages in [RFC3775]. Firstly, in order that HA and FR offer a
subnet prefix and a domain name for the MN, a router advertisement
(RA) message is newly defined. Using this RA message, the MN can make
a new Uniform Resource Identifier (URI) as well as a home address
(HoA) or a care-of address (CoA). Secondly, in order that the MN
solicits the HA or FR for the RA with a domain name as well as a
subnet prefix, a router solicitation (RS) message is newly defined.
Lastly, when the MN changes its subnet and thus makes the CoA and
the new URI, to do simultaneously both location registration for SIP
and home registration for Mobile IPv6 with the HA, a binding update
(BU) message is newly defined.
In the proposed mechanism, the MN doesn't require dynamic host
configuration protocol (DHCP) [RFC1541] and thus both home and
foreign subnets don't need DHCP servers. On the other hand, existing
mechanisms on Mobile IPv4 required DHCP for the MN, and used DHCP
servers for the MN to get the HoA or CoA and the new URI, as shown in
existing works. In addition, the proposed mechanism provides the
efficient optimized routing where speech packets sent by the CN are
routed directly to the MN, whereas existing mechanisms could not due
to the triangle routing.
2. Requirements
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 [RFC2119].
3. Network Architecture for Proposed Mechanism
In this draft, a new mechanism for SIP over Mobile IPv6 is proposed
for a wireless mobile network. The network considered for the
proposed mechanism consists of a mobile node (MN), a correspondent
node (CN), a home agent (HA), and a foreign router (FR).
The MN acts as a user agent (UA) for SIP as well as a mobile host for
Mobile IPv6. That is, in addition to its inherent functions for
Mobile IPv6, the MN creates a new SIP request and generates a
response to a SIP request. The CN also acts as a user agent (UA) for
SIP as well as a peer node with which a mobile node is communicating
for Mobile IPv6.
The HA on home subnet acts as a redirect server and a registrar for
SIP as well as a home router for Mobile IPv6. That is, the HA
provides its inherent functions of Mobile IPv6, such as a router
advertisement and a home registration for a mobile node (MN). In
addition, for SIP, the HA accepts a location registration request of
the MN, places the information it receives in this request into
a location database, and returns the location information of the MN
to the CN. Thus, the binding cache in the HA contains location
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information for SIP as well as home registration entries for Mobile
IPv6. On the other side, the FR provides only a router advertisement
for the MN.
4. New Messages for Proposed Mechanism
In this section, to implement the proposed mechanism, some messages
used in network layer are newly defined by adding some fields to
existing messages in [RFC3775], such as a router advertisement, a
router solicitation and a binding update.
4.1 New Router Advertisement Message
In order that HA and FR offer a subnet prefix and a domain name for
the MN, a router advertisement (RA) message is newly defined by
adding some fields to existing message in [RFC3775]. Using this RA
message, the MN can make a new Uniform Resource Identifier (URI)
as well as a home address (HoA) or a care-of address (CoA).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H|D|Reserv | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Domain Information +
| (ex: kpu.ac.kr or ssslab.kpu.ac.kr) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig.1 New Router Advertisement Message
o Domain Name Flag (D) : This bit is set in a RA to indicate that
the router sending this RA also include a domain name of current
subnet.
o Reserved : Reduced from a 5-bit field to a 4-bit field to account
for the addition of the above bit.
o Domain Name : The domain name of current subnet where the MN is
attached. The data in the domain name should be encoded according to
DNS encoding rules. For example, kpu.ac.kr or ssslab.kpu.ac.kr.
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o Subtype: Subtype field defines the link type of the mobile node
included in the Link Characteristic Information field.
o Other fields : See [RFC3775]
The source address field in the IP header carrying this message is
the link-local address assigned to the interface from which this
message is sent. The destination address field in the IP header
carrying this message is typically the source address of an invoking
router solicitation or the all-nodes multicast address.
4.2 New Router Solicitation Message
In order that the MN solicits the HA or FR for a router advertisement
with a domain name as well as a subnet prefix, a router solicitation
(RS) message is newly defined by adding some fields to existing
message in [RFC3775].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig.2 New Router Solicitation Message
o Domain Name Request Flag (D) : This bit is set in a RS to
indicate that the MN requests a domain name of current subnet.
o Reserved : Reduced from a 32-bit field to a 31-bit field to account
for the addition of the above bit.
o Other fields : See [RFC3775]
The source address field in the IP header carrying this message is
the IP address of MN. The destination address field in the IP header
carrying this message is typically the all-routers multicast address.
4.3 New Binding Update Message
When the MN changes its subnet and thus makes the CoA and the new
URI, to do simultaneously both location registration for SIP and home
registration for Mobile IPv6 with the HA, a new binding update (BU)
message is newly defined by adding some fields to existing message
in [RFC3775].
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Header Ext Len | Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ HoA +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ New URI +
| (ex: pskim@kpu.ac.kr or pskim@ssslab.kpu.ac.kr) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig.3 New Binding Update Message
o Option Type : 10 (or any available value)
o New URI : The new URI of the MN. For example, pskim@kpu.ac.kr or
pskim@ssslab.kpu.ac.kr
o Other fields : See [RFC3775]
The source address field in the IP header carrying this message is
the CoA of the MN. The destination address field in the IP header
carrying this message is the IP address of the HA. This BU message
contains the Home Address destination option that has the HoA of
the MN.
5. Basic Operation Procedure of Proposed Mechanism
In this section, the basic operation of the proposed mechanism is
explained in detail. The MN is assumed to be the callee and the CN is
assumed to be the caller. It is also assumed that the MN's HoA is
3ffe:2e01:2a:100::10 and URI is pskim@kpu.ac.kr in a home subnet.
The CN's URI is assumed to be peter@mipv6.com.
When the MN changes its subnet and thus attaches to a foreign subnet,
it will receive solicited RA or unsolicited RA from the FR. To
receive the solicited RA, the MN sends the RS with setting Domain
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Name Request Flag (D) to the FR as shown in Fig. 2. Note that this
RS would be optional. The RA in Fig. 1 contains the subnet prefix for
the MN's CoA configuration and the domain name for the MN's new URI
configuration. In foreign subnet, the address prefix is
3ffe:2e01:2a:200::/64 and the domain name is ssslab.kpu.ac.kr. Then,
the MN makes the CoA as 3ffe:2e01:2a:200::10 and the new URI as
pskim@ssslab.kpu.ac.kr.
To do simultaneously both location registration for SIP and home
registration for Mobile IPv6 with the HA, the MN sends the BU with
both CoA and new URI to the HA, using the newly defined message in
Fig. 3. If the HA accepts the BU, it update its binding cache entry
for the MN. If the URI is not changed, the only CoA is updated in the
binding cache. This binding cache is an effective database containing
mappings among the original URI, the current URI, the HoA and the
CoA.
The CN with peter@mipv6.com wants to invite the MN with
pskim@kpu.ac.kr The CN translates the domain name kpu.ac.kr to a
numeric IP address, by a DNS lookup, where the HA may be found. An
INVITE request is generated and sent to this HA. Note that the HA
does not issue any SIP requests of its own. After receiving a request
other than CANCEL, the HA either refuses the request or gathers the
MN's current location information from the binding cache and returns
a final response of class 3xx. For well-formed CANCEL requests, it
returns a 2xx response. Then, when the HA accepts the invitation,
it gathers the MN's current location information, such as the HoA
3ffe:2e01:2a:100::10, the CoA 3ffe:2e01:2a:200::10 and the new URI
pskim@ssslab.kpu.ac.kr, from the binding cache. Thus, the HA
returns a 302 response (Moved Temporarily) with MN's current location
information. The CN acknowledges the response with an ACK request to
the HA. Then, the CN issues a new INVITE request based on the MN's
current URI pskim@ssslab.kpu.ac.kr. This request is sent to the MN's
CoA 3ffe:2e01:2a:200::10. In this case, the call succeeds and a
response indicating this is sent to the CN. The signaling is
completed with an ACK from the CN to the MN. After this call setup,
the real speech communication is going on.
In the proposed mechanism, the MN doesn' require dynamic host
configuration protocol (DHCP) and thus both home and foreign subnets
don't need DHCP servers. On the other hand, existing mechanisms on
Mobile IPv4 required DHCP for the MN, and used DHCP servers for the
MN to get the HoA or CoA and the new URI, as shown in existing
mechanisms. In addition, the proposed mechanism uses the optimized
routing between the MN and the CN. That is, speech packets sent by
the caller are routed directly to the callee. On the other hand, in
existing mechanisms, speech packets that are sent by the caller to
the callee connected to a foreign subnet are routed first to the
callee's HA and then tunneled to the callee's CoA. Therefore, the
proposed mechanism might be more efficient in terms of speech delay
and resource consumption than existing mechanisms, because, in
general, the speech packets will have to traverse fewer subnets on
their way to their destination.
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6. References
[RFC3261] Rosenberg, J. et al, "SIP: Session Initiation Protocol",
RFC 3261, June 2002.
[RFC2002] Perkins, C., "IP Mobility Support", RFC 2002, October 1996
[RFC3775] Johnson, D. B., "Mobility Support in IPv6", RFC 3775,
June 2004
[RFC1541] Droms, R., "Dynamic Host Configuration Protocol", RFC 1541,
October 1993
[Moh1999] Moh, M. et al, "Mobile IP telephony: mobility support
of SIP", Proc. Int. Conf. on Computer Communications and
Networks, pp. 554-559, 1999
[Seol2002] Seol, S. et al, "Experiments and analysis of voice over
Mobile IP", Proc. IEEE Int. Symposium on Personal, Indoor
and Mobile Radio Communications, pp. 997-981, 2002
[Kwon2002] Kwon, T. et al, "Mobility management for VoIP service:
Mobile IP vs. SIP", IEEE Wireless Communications, Vol.9,
No. 5, pp 66-75, 2002
Authors' Addresses
Pyung-Soo Kim
Department of Electronics Engineering,
Korea Polytechnic University,
2121 Jungwang-Dong, Shiheung City,
Gyeonggi-Do 429-793
KOREA
Phone: +82 31 496 8413
EMail: pskim@kpu.ac.kr
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