Network Working Group B. Patil
Internet-Draft Nokia
Intended status: Standards Track K. Chowdhury
Expires: September 9, 2009 Starent Networks
D. Premec
Nokia Siemens Networks
March 8, 2009
DHCP options for Access Point Name and attach type indication
draft-patil-dhc-apn-attachtype-options-01.txt
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Abstract
Access Point Names are used in wireless networks which are based on
3GPP standards to identify a specific gateway element. A mobile node
which attaches via a 3GPP access network indicates the gateway to
which connectivity is desired by providing the gateways access point
name, in the network attach signaling messages. This document
specifies a new DHCP option which enables the mobile node to request
connectivity to a gateway, identified by the access point name, in
DHCP messages. A mobile node whose mobility is managed by the
network using Proxy Mobile IPv6 protocol may perform a handover from
one access technology to another. This document defines a DHCP
option which enables the host to indicate to Proxy Mobile IPv6
elements in the access network if the attachment via the new
interface is a handover or a new connection.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. DHCP options for APN and Attach-type . . . . . . . . . . . . . 6
4.1. DHCPv6 Attach Information option . . . . . . . . . . . . . 6
4.2. DHCPv4 Attach Information option . . . . . . . . . . . . . 7
4.3. Attach Info Data . . . . . . . . . . . . . . . . . . . . . 7
4.4. Option Usage . . . . . . . . . . . . . . . . . . . . . . . 8
5. Mobile Node/host behavior . . . . . . . . . . . . . . . . . . 9
6. Access Router/NAS/DHCP relay agent behavior . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Requirements notation
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].
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2. Introduction
Cellular data networks which are based on 3GPP standards [TS-23.060],
i.e GPRS (General Packet Radio Service) define the concept of an
Access Point Name (APN). The APN is an FQDN and identifies a
specific gateway in the core network. Operators choose to offer
different types of services via specific gateways. For example
gateway 1 identified by APN1 offers Internet connectivity while
gateway 2 identified by APN2 offers multi-media messaging service
(MMS). A mobile node which attaches via a 3GPP access network
indicates the gateway to which it needs connectivity by including the
APN parameter in the network attachment signaling messages. The APN
information from the UE received in the attach signaling messages
enables the access network to establish a tunnel to the appropriate
gateway in the core. The mobile node chooses the APN based on the
application in use or policies. The application is configured to
connect to the gateway through which the operator provides the
service.
Proxy Mobile IPv6 [RFC5213] is a network based mobility protocol. A
host which is attached to a Proxy MIP6 (PMIP6) domain through an
access network of type X may initiate a handover when it attaches to
another access network of type Y. In order to ensure that the Local
Mobility Agent (LMA) in the PMIP6 domain assigns the host the same
prefix/address, the Mobility access gateway (MAG) in the network to
which the host performs the handover to (i.e type Y) needs to
indicate that it is a handover by setting the flag in the Proxy
Binding Update (PBU) mesage sent by the MAG to the LMA . In the
absence of any context transfer from the previous MAG to the new MAG,
the host has to provide this information to the new MAG. The host
can indicate that the network attachment to the access network of
type Y is a handover. A multiinterfaced host may attach via a second
interface to the same PMIP6 domain via which the host using another
interface is already connected. In such cases it is essential to
indicate if the new network attachment is to be treated as a handover
from the previous interface or is a new session,.
This document specifies DHCP options for DHCPv4 and DHCPv6 which
enable the host to indicate the gateway identified by an APN to which
connectivity is desired and the attach-type indicator to be used in
the case of Proxy MIP6.
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3. Terminology
This document refers to [RFC5213]. The term Access Point Name is
defined in [TS-23.003] in section 9.1. It is also defined below as
per the 3GPP definition.
Access Point Name:
In the GPRS backbone, an Access Point Name (APN) is a reference
to a GGSN (Gateway GPRS Serving Node).
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4. DHCP options for APN and Attach-type
The use of APN has been limited to 3GPP networks. In the case of
3GPP accesses such as GERAN, UMTS and HSPA, a layer 2 mechanism is
specified which enables the mobile node to indicate the APN parameter
to the access network, and thereby being assigned a specific GGSN in
the core. Recent developments now allow non-3GPP accesses such as
HRPD and WiMAX to also connect to a 3GPP core network. These access
types do not have a specific mechanism by which a mobile node can
indicate the APN to establish a connection with. Specifying this
capability as a DHCP option enables the mobile node to indicate the
APN to establish a connection with at the time of network entry.
Proxy Mobile IPv6 [RFC5213] does not require any changes on the host
in order to support mobility. A Proxy MIP6 domain can span multiple
access networks of different technologies. An MN which is attached
via an interface (I1) to a PMIP6 domain may attach via another
interface (I2). If the MN wants the sessions which are currently
served by interface I1 to be moved to interface I2, it needs to
indicate that the new network attachment is of type handover. The MN
can indicate the attach type via a DHCP option during network entry
and the MAG in the PMIP6 domain can use this information in the
signaling to the LMA appropriately.
4.1. DHCPv6 Attach Information option
This option enables the DHCPv6 host to indicate the access point name
to which the connection needs to be established with and whether the
connection being established is the handover from another interface
or a new attachment. The host (DHCP client) includes this option in
the DHCP Request message sent to the access gateway/NAS (Network
Access Server) which acts as the DHCP server or relay.
The format of the DHCPv6 OPTION_ATTACH_INFO is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ATTACH_INFO | Option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attach_Info_Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Option-code OPTION_ATTACH_INFO To be assigned by IANA
Option-len The length of the Attach_Info_Data in units of octets
Attach_Info_Data see section Section 4.3
4.2. DHCPv4 Attach Information option
This option enables the DHCPv4 host to indicate the access point name
to which the connection needs to be established with and whether the
connection being established is the handover from another access
network or a new attachment. The host (DHCP client) includes this
option in the DHCP Request message sent to the access gateway/NAS
(Network Access Server) which acts as the DHCP server or relay.
The format of the DHCPv4 ATTACH_INFO option is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATTACH_INFO | length | Attach_Info_Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code ATTACH_INFO To be assigned by IANA
Option-len The length of the ATTACH_INFO option is variable, it is
given in units of octets
Attach_Info_Data see section Section 4.3
4.3. Attach Info Data
The Attach_Info_Data defines a common layout shared by both the
DHCPv6 and DHCPv4 Attach Information options. It consists of two
fields: the Attach_Type and the Access_Point_Name which enable the
host to indicate the type of connection required.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attach_Type | Access_Point_Name...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Attach_Type The Attach_Type specifies the following values:
Handover: 0
New Service Flow: 1
Reserved: 2-255
Access_Point_Name The Access_Point_Name indicates the network node
providing the service to the host
The Attach_Type field enables the host to indicate if the attach to
the network is to be interpreted as a handover or establishment of a
new connection. This is applicable in the case the host is attaching
to a PMIP6 domain.
The Access_Point_Name field enables the host to indicate the APN to
which the connection needs to be established with. It is formatted
as a character string consisting of characters from the NVT ASCII
character set and it SHOULD NOT contain the trailing NULL in
accordance with section 2 of [RFC2132].
The host (DHCP client) includes the Attach_Type and Access_Point_Name
in the DHCP Request message sent to the Access Router/Mobility Access
Gateway which acts as a DHCP relay or in some cases a DHCP server.
The MAG uses the ATTACH_Type to construct the signaling message to
the Local Mobility Agent as per [RFC5213] . The MAG uses the
Access_Point_Name to select the correct LMA which provides the
service requested by the host.
4.4. Option Usage
The requesting and sending of the proposed DHCP options follows the
rules specified in [RFC3315] for DHCPv6 options and in [RFC2131] for
DHCPv4 options.
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5. Mobile Node/host behavior
A mobile node includes the Attach Information option when attaching
to an access network which is served by a 3GPP core. The option is
not required for access technologies which have layer 2 mechanisms
for conveying the APN and the attach type. The MN/host is aware of
the access type through which it is connecting and hence can make the
decision to include the Attach Information option. The MN includes
the Attach Information Option in the DHCP Request message sent to the
access router/NAS.
The MN is aware when it attaches via another access type if it is to
be treated as a handover. If the MN prefers to move the sessions
from the previous interface to the new interface it needs to indicate
that it is a handover by appropriately setting the Attach_Type in the
Attach Information option.
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6. Access Router/NAS/DHCP relay agent behavior
An access router/gateway which also acts as a NAS and includes either
a DHCP relay function or in some cases acts as a DHCP server receives
the DHCP request message which includes Attach Information option.
The gateway uses the Access_Point_Name from the Attach Information
option to establish a bi-directional tunnel with the appropriate
gateway in the 3GPP core network. The NAS/gateway resolves the IP
address of the gateway in the core from the APN via DNS.
The NAS/access gateway which receives the Attach Information option
from the MN in the DHCP Request relays this information to the PMIP6
MAG function. The MAG uses the Attach_Type from the Attach
Information option to set the flags in the proxy binding update (PBU)
sent to the Local Mobiliity agent (LMA).
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7. Security Considerations
The options specified in this I-D do not introduce any security
vulnerabilities which are new.
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8. IANA Considerations
IANA is requested to assign the option codes for the DHCPv4 Attach
Information option and for the DHCPv6 Attach Information option.
3GPP TS 23.060 v 5.2.0, "General Packet Radio Service (GPRS); Service
description; Stage 2(Release 5)", June 2002.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[TS-23.003]
"3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Numbering,
addressing and identification (Release 8)", 3GPP TS 23.003
v 8.3.0, December 2008.
[TS-23.060]
"General Packet Radio Service (GPRS); Service description;
Stage 2 (Release 8)", 3GPP TS 23.060 v 8.3.0,
December 2008.
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Authors' Addresses
Basavaraj Patil
Nokia
6021 Connection Drive
Irving, TX 75039
USA
Email: basavaraj.patil@nokia.com
Kuntal Chowdhury
Starent Networks
20 International Place
Tewksbury, MA 01876
USA
Email: kchowdhury@starentnetworks.com
Domagoj Premec
Nokia Siemens Networks
Heinzelova 70a
Zagreb, 10000
Croatia
Phone: +395 (1) 6105 293
Email: domagoj.premec.ext@nsn.com
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