Diameter PMIPv6: Diameter Proxy Mobile IPv6: Mobile Access Gateway and Local Mobility Anchor Interaction with Diameter Server
How Proxy Mobile IPv6 gateways and anchors ask a home AAA server for per-device rules and permission.
Korhonen, J., Ed., Bournelle, J., Chowdhury, K., Muhanna, A., and U. Meyer, "Diameter Proxy Mobile IPv6: Mobile Access Gateway and Local Mobility Anchor Interaction with Diameter Server", RFC 5779, DOI 10.17487/RFC5779, February 2010, <https://www.rfc-editor.org/info/rfc5779>.
@misc{rfc5779,
series = {Request for Comments},
number = 5779,
howpublished = {RFC 5779},
publisher = {RFC Editor},
doi = {10.17487/RFC5779},
url = {https://www.rfc-editor.org/info/rfc5779},
author = {J. Korhonen and J. Bournelle and K. Chowdhury and A. Muhanna and U. Meyer},
title = {{Diameter Proxy Mobile IPv6: Mobile Access Gateway and Local Mobility Anchor Interaction with Diameter Server}},
pagetotal = 20,
year = 2010,
month = feb,
} RFC text
Contents
Internet Engineering Task Force (IETF) J. Korhonen, Ed.
Request for Comments: 5779 Nokia Siemens Network
Category: Standards Track J. Bournelle
ISSN: 2070-1721 Orange Labs
K. Chowdhury
Cisco Systems
A. Muhanna
Ericsson
U. Meyer
RWTH Aachen
February 2010
Diameter Proxy Mobile IPv6: Mobile Access Gateway and
Local Mobility Anchor Interaction with Diameter Server
Abstract
This specification defines Authentication, Authorization, and
Accounting (AAA) interactions between Proxy Mobile IPv6 entities
(both Mobile Access Gateway and Local Mobility Anchor) and a AAA
server within a Proxy Mobile IPv6 Domain. These AAA interactions are
primarily used to download and update mobile node specific policy
profile information between Proxy Mobile IPv6 entities and a remote
policy store.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5779.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................4
2. Terminology and Abbreviations ...................................4
3. Solution Overview ...............................................5
4. Generic Application Support and Command Codes ...................6
4.1. MAG-to-HAAA Interface ......................................6
4.2. LMA-to-HAAA Interface ......................................7
4.2.1. General Operation and Authorization of PBU ..........7
4.2.2. Updating LMA Address to HAAA ........................8
4.2.3. Mobile Node Address Update and Assignment ...........8
5. Attribute Value Pair Definitions ................................9
5.1. MIP6-Agent-Info AVP ........................................9
5.2. PMIP6-IPv4-Home-Address AVP ...............................10
5.3. MIP6-Home-Link-Prefix AVP .................................10
5.4. PMIP6-DHCP-Server-Address AVP .............................10
5.5. MIP6-Feature-Vector AVP ...................................10
5.6. Mobile-Node-Identifier AVP ................................11
5.7. Calling-Station-Id AVP ....................................12
5.8. Service-Selection AVP .....................................12
5.9. Service-Configuration AVP .................................13
6. Proxy Mobile IPv6 Session Management ...........................13
6.1. Session-Termination-Request ...............................14
6.2. Session-Termination-Answer ................................14
6.3. Abort-Session-Request .....................................14
6.4. Abort-Session-Answer ......................................14
7. Attribute Value Pair Occurrence Tables .........................14
7.1. MAG-to-HAAA Interface .....................................15
7.2. LMA-to-HAAA Interface .....................................15
8. Example Signaling Flows ........................................15
9. IANA Considerations ............................................17
9.1. Attribute Value Pair Codes ................................17
9.2. Namespaces ................................................17
10. Security Considerations .......................................17
11. Acknowledgements ..............................................17
12. References ....................................................18
12.1. Normative References .....................................18
12.2. Informative References ...................................18
1. Introduction
This specification defines Authentication, Authorization, and
Accounting (AAA) interactions between a Mobile Access Gateway (MAG)
and a AAA server, and between a Local Mobility Anchor (LMA) and a AAA
server within a Proxy Mobile IPv6 (PMIPv6) Domain [RFC5213]. These
AAA interactions are primarily used to download and update mobile
node (MN) specific policy profile information between PMIPv6 entities
(a MAG and an LMA) and a remote policy store.
Dynamic assignment and downloading of an MN's policy profile
information to a MAG from a remote policy store is a desirable
feature to ease the deployment and network maintenance of larger
PMIPv6 domains. For this purpose, the same AAA infrastructure that
is used for authenticating and authorizing the MN for a network
access can be leveraged to download some or all of the necessary
policy profile information to the MAG.
Once the network has authenticated the MN, the MAG sends a Proxy
Binding Update (PBU) to the LMA in order to set up a mobility session
on behalf of the MN. When the LMA receives the PBU, the LMA may need
to authorize the received PBU against the AAA infrastructure. The
same AAA infrastructure that can be used for the authorization of the
PBU, is also used to update the remote policy store with the LMA-
provided MN specific mobility session-related information.
In the context of this specification, the home AAA (HAAA) server
functionality is co-located with the remote policy store. The NAS
functionality may be co-located with the MAG function in the network
access router. Diameter [RFC3588] is the used AAA protocol.
2. Terminology and Abbreviations
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].
The general terminology used in this document can be found in
[RFC5213] and [NETLMM-PMIP6]. The following additional or clarified
terms are also used in this document:
Network Access Server (NAS):
A device that provides an access service for a user to a network.
In the context of this document, the NAS may be integrated into or
co-located to a MAG. The NAS contains a Diameter client function.
Home AAA (HAAA):
An Authentication, Authorization, and Accounting (AAA) server
located in user's home network. A HAAA is essentially a Diameter
server.
3. Solution Overview
This document addresses the AAA interactions and AAA-based session
management functionality needed in the PMIPv6 Domain. This document
defines Diameter-based AAA interactions between the MAG and the HAAA,
and between the LMA and the HAAA.
The policy profile is downloaded from the HAAA to the MAG during the
MN attachment to the PMIPv6 Domain. Figure 1 shows the participating
network entities. This document, however, concentrates on the MAG,
LMA, and the HAAA (the home Diameter server).
+--------+
| HAAA & | Diameter +-----+
| Policy |<---(2)-->| LMA |
| Store | +-----+
+--------+ | <--- LMA-Address
^ |
| // \\
+---|------------- //---\\----------------+
( | IPv4/IPv6 // \\ )
( | Network // \\ )
+---|-----------//---------\\-------------+
| // \\
Diameter // <- Tunnel1 \\ <- Tunnel2
(1) // \\
| |- MAG1-Address |- MAG2-Address
| +----+ +----+
+---->|MAG1| |MAG2|
+----+ +----+
| |
| |
[MN1] [MN2]
Legend:
(1): MAG-to-HAAA interaction is described in Section 7.1
(2): LMA-to-HAAA interaction is described in Section 7.2
Figure 1: Proxy Mobile IPv6 Domain Interaction
with Diameter HAAA Server
When an MN attaches to a PMIPv6 Domain, a network access
authentication procedure is usually started. The choice of the
authentication mechanism is specific to the access network
deployment, but could be based on the Extensible Authentication
Protocol (EAP) [RFC3748]. During the network access authentication
procedure, the MAG acting as a NAS queries the HAAA through the AAA
infrastructure using the Diameter protocol. If the HAAA detects that
the subscriber is also authorized for the PMIPv6 service, PMIPv6
specific information is returned along with the successful network
access authentication answer to the MAG.
After the MN has been successfully authenticated, the MAG sends a PBU
to the LMA based on the MN's policy profile information. Upon
receiving the PBU, the LMA interacts with the HAAA and fetches the
relevant parts of the subscriber policy profile and authorization
information related to the mobility service session. In this
specification, the HAAA has the role of the PMIPv6 remote policy
store.
4. Generic Application Support and Command Codes
This specification does not define new Application-IDs or Command
Codes for the MAG-to-HAAA or for the LMA-to-HAAA Diameter
connections. Rather, this specification is generic to any Diameter
application (and their commands) that is suitable for a network
access authentication and authorization. Example applications
include NASREQ [RFC4005] and EAP [RFC4072].
4.1. MAG-to-HAAA Interface
The MAG-to-HAAA interactions are primarily used for bootstrapping
PMIPv6 mobility service session when an MN attaches and authenticates
to a PMIPv6 Domain. This includes the bootstrapping of PMIPv6
session-related information. The same interface may also be used for
accounting. The MAG acts as a Diameter client.
Whenever the MAG sends a Diameter request message to the HAAA, the
User-Name AVP SHOULD contain the MN's identity unless the identity is
being suppressed for policy reasons -- for example, when identity
hiding is in effect. The MN identity, if available, MUST be in
Network Access Identifier (NAI) [RFC4282] format. At minimum, the
home realm of the MN MUST be available at the MAG when the network
access authentication takes place. Otherwise, the MAG is not able to
route the Diameter request messages towards the correct HAAA. The MN
identity used on the MAG-to-HAAA interface and in the User-Name AVP
MAY entirely be related to the network access authentication, and
therefore not suitable to be used as the MN-ID mobility option value
in the subsequent PBU / Proxy Binding Acknowledgement (PBA) messages.
See the related discussion on MN identities in Sections 4.2 and 5.6.
For the session management and service authorization purposes,
session state SHOULD be maintained on the MAG-to-HAAA interface. See
the discussion in Section 5.8.
4.2. LMA-to-HAAA Interface
The LMA-to-HAAA interface may be used for multiple purposes. These
include the authorization of the incoming PBU, updating the LMA
address to the HAAA, delegating the assignment of the MN-HNP (home
network prefix) or the IPv4-HoA (home address) to the HAAA, and for
accounting and PMIPv6 session management. The primary purpose of
this interface is to update the HAAA with the LMA address information
in case of dynamically assigned LMA, and exchange the MN address
assignment information between the LMA and the HAAA.
The LMA-to-HAAA interface description is intended for different types
of deployments and architectures. Therefore, this specification only
outlines AVPs and considerations that the deployment specific
Diameter applications need to take into account from the PMIPv6 and
LMA's point of view.
4.2.1. General Operation and Authorization of PBU
Whenever the LMA sends a Diameter request message to the HAAA, the
User-Name AVP SHOULD contain the MN's identity. The LMA-provided
identity in the User-Name AVP is strongly RECOMMENDED to be the same
as the MN's identity information in the PBU MN-ID [RFC4283] [RFC5213]
mobility option. The identity SHOULD also be the same as used on the
MAG-to-HAAA interface, but in case those identities differ the HAAA
MUST have a mechanism of mapping the MN identity used on the MAG-to-
HAAA interface to the identity used on the LMA-to-HAAA interface.
If the PBU contains the MN Link-Layer Identifier option, the Calling-
Station-Id AVP SHOULD be included in the request message containing
the received link-layer identifier. Furthermore, if the PBU contains
the Service Selection mobility option [RFC5149], the Service-
Selection AVP SHOULD be included in the request message containing
the received service identifier. Both the MN link-layer identifier
and the service selection can be used to provide more information for
the PBU authorization step in the HAAA.
The Auth-Request-Type AVP MUST be set to the value AUTHORIZE_ONLY.
The Diameter session-related aspects discussed in Section 6 need to
be taken into consideration when designing the Diameter application
for the LMA-to-HAAA interface. If the HAAA is not able to authorize
the subscriber's mobility service session, then the reply message to
the LMA MUST have the Result-Code AVP set to value
DIAMETER_AUTHORIZATION_REJECTED (5003) indicating a permanent
failure. A failed authorization obviously results in a rejection of
the PBU, and a PBA with an appropriate error Status Value MUST be
sent back to the MAG.
The authorization step MUST be performed at least for the initial PBU
session up to a mobility session, when the LMA-to-HAAA interface is
deployed. For the subsequent re-registration and handover PBUs, the
authorization step MAY be repeated (in this case, the LMA-to-HAAA
interface should also maintain an authorization session state).
4.2.2. Updating LMA Address to HAAA
In case of a dynamic LMA discovery and assignment [NETLMM-LMA], the
HAAA and the remote policy store may need to be updated with the
selected LMA address information. The update can be done during the
PBU authorization step using the LMA-to-HAAA interface. This
specification uses the MIP6-Agent-Info AVP and its MIP-Home-Agent-
Address and MIP-Home-Agent-Host sub-AVPs for carrying the LMA's
address information from the LMA to the HAAA. The LMA address
information in the request message MUST contain the IP address of the
LMA or the Fully Qualified Domain Name (FQDN) identifying uniquely
the LMA, or both. The LMA address information refers to the PMIPv6
part of the LMA, not necessarily the LMA part interfacing with the
AAA infrastructure.
This specification does not define any HAAA-initiated LMA relocation
functionality. Therefore, when the MIP6-Agent-Info AVP is included
in Diameter answer messages sent from the HAAA to the LMA, the HAAA
indicates this by setting the MIP-Home-Agent-Address AVP to all
zeroes address (e.g., 0::0) and not including the MIP-Home-Agent-Host
AVP.
4.2.3. Mobile Node Address Update and Assignment
The LMA and the HAAA use the MIP6-Home-Link-Prefix AVP to exchange
the MN-HNP when appropriate. Similarly, the LMA and the HAAA use the
PMIP6-IPv4-Home-Address AVP to exchange the IPv4-MN-HoA when
appropriate. These AVPs are encapsulated inside the MIP6-Agent-Info
AVP. The MN address information exchange is again done during the
PBU authorization step. The HAAA MAY also use the LMA-provided MN
address information as a part of the information used to authorize
the PBU.
Which entity is actually responsible for the address management is
deployment specific within the PMIPv6 Domain and MUST be pre-agreed
on per deployment basis. When the LMA is responsible for the address
management, the MIP6-Agent-Info AVP is used to inform the HAAA and
the remote policy store of the MN-HNP/IPv4-MN-HoA assigned to the MN.
It is also possible that the LMA delegates the address management to
the HAAA. In this case, the MN-HNP/IPv4-MN-HoA are set to undefined
addresses (as described in Section 5.1) in the Diameter request
message sent from the LMA to the HAAA. The LMA expects to receive
the HAAA assigned HNP/IPv4-MN-HoA in the corresponding Diameter
answer message.
5. Attribute Value Pair Definitions
This section describes Attribute Value Pairs (AVPs) defined by this
specification or re-used from existing specifications in a PMIPv6
specific way. Derived Diameter AVP Data Formats such as Address and
UTF8String are defined in Section 4.3 of [RFC3588]. Grouped AVP
values are defined in Section 4.4 of [RFC3588].
5.1. MIP6-Agent-Info AVP
The MIP6-Agent-Info grouped AVP (AVP Code 486) is defined in
[RFC5447]. The AVP is used to carry LMA addressing-related
information and an MN-HNP. This specification extends the MIP6-
Agent-Info with the PMIP6-IPv4-Home-Address AVP using the Diameter
extensibility rules defined in [RFC3588]. The PMIP6-IPv4-Home-
Address AVP contains the IPv4-MN-HoA.
The extended MIP6-Agent-Info AVP results in the following grouped
AVP. The grouped AVP has the following modified ABNF (as defined in
[RFC3588]):
MIP6-Agent-Info ::= < AVP-Header: 486 >
*2[ MIP-Home-Agent-Address ]
[ MIP-Home-Agent-Host ]
[ MIP6-Home-Link-Prefix ]
[ PMIP6-IPv4-Home-Address ]
* [ AVP ]
If the MIP-Home-Agent-Address is set to all zeroes address (e.g.,
0::0), the receiver of the MIP6-Agent-Info AVP MUST ignore the MIP-
Home-Agent-Address AVP.
5.2. PMIP6-IPv4-Home-Address AVP
The PMIP6-IPv4-Home-Address AVP (AVP Code 505) is of type Address and
contains an IPv4 address. This AVP is used to carry the IPv4-MN-HoA,
if available, from the HAAA to the MAG. This AVP SHOULD only be
present when the MN is statically provisioned with the IPv4-MN-HoA.
Note that proactive dynamic assignment of the IPv4-MN-HoA by the HAAA
may result in unnecessary reservation of IPv4 address resources,
because the MN may considerably delay or completely bypass its IPv4
address configuration.
The PMIP6-IPv4-Home-Address AVP is also used on the LMA-to-HAAA
interface. The AVP contains the IPv4-MN-HoA assigned to the MN. If
the LMA delegates the assignment of the IPv4-MN-HoA to the HAAA, the
AVP MUST contain all zeroes IPv4 address (i.e., 0.0.0.0) in the
request message. If the LMA delegated the IPv4-MN-HoA assignment to
the HAAA, then the AVP contains the HAAA assigned IPv4-MN-HoA in the
response message.
5.3. MIP6-Home-Link-Prefix AVP
The MIP6-Home-Link-Prefix AVP (AVP Code 125) is defined in [RFC5447].
This AVP is used to carry the MN-HNP, if available, from the HAAA to
the MAG. The low 64 bits of the prefix MUST be all zeroes.
The MIP6-Home-Link-Prefix AVP is also used on the LMA-to-HAAA
interface. The AVP contains the prefix assigned to the MN. If the
LMA delegates the assignment of the MN-HNP to the HAAA, the AVP MUST
contain all zeroes address (i.e., 0::0) in the request message. If
the LMA delegated the MN-HNP assignment to the HAAA, then the AVP
contains the HAAA-assigned MN-HNP in the response message.
5.4. PMIP6-DHCP-Server-Address AVP
The PMIP6-DHCP-Server-Address AVP (AVP Code 504) is of type Address
and contains the IP address of the Dynamic Host Configuration
Protocol (DHCP) server assigned to the MAG serving the newly attached
MN. If the AVP contains a DHCPv4 [RFC2131] server address, then the
Address type MUST be IPv4. If the AVP contains a DHCPv6 [RFC3315]
server address, then the Address type MUST be IPv6. The HAAA MAY
assign a DHCP server to the MAG in deployments where the MAG acts as
a DHCP Relay [NETLMM-PMIP6].
5.5. MIP6-Feature-Vector AVP
The MIP6-Feature-Vector AVP is originally defined in [RFC5447]. This
document defines new capability flag bits according to the IANA rules
in RFC 5447.
PMIP6_SUPPORTED (0x0000010000000000)
When the MAG/NAS sets this bit in the MIP6-Feature-Vector AVP, it
is an indication to the HAAA that the NAS supports PMIPv6. When
the HAAA sets this bit in the response MIP6-Feature-Vector AVP, it
indicates that the HAAA also has PMIPv6 support. This capability
bit can also be used to allow PMIPv6 mobility support in a
subscription granularity.
IP4_HOA_SUPPORTED (0x0000020000000000)
Assignment of the IPv4-MN-HoA is supported. When the MAG sets
this bit in the MIP6-Feature-Vector AVP, it indicates that the MAG
implements a minimal functionality of a DHCP server (and a relay)
and is able to deliver IPv4-MN-HoA to the MN. When the HAAA sets
this bit in the response MIP6-Feature-Vector AVP, it indicates
that the HAAA has authorized the use of IPv4-MN-HoA for the MN.
If this bit is unset in the returned MIP6-Feature-Vector AVP, the
HAAA does not authorize the configuration of IPv4 address.
LOCAL_MAG_ROUTING_SUPPORTED (0x0000040000000000)
Direct routing of IP packets between MNs anchored to the same MAG
is supported as described in Sections 6.10.3 and 9.2 of [RFC5213].
When a MAG sets this bit in the MIP6-Feature-Vector, it indicates
that routing IP packets between MNs anchored to the same MAG is
supported, without reverse tunneling packets via the LMA or
requiring any Route Optimization-related signaling (e.g., the
Return Routability Procedure in [RFC3775]) prior direct routing.
If this bit is cleared in the returned MIP6-Feature-Vector AVP,
the HAAA does not authorize direct routing of packets between MNs
anchored to the same MAG. The MAG SHOULD support this policy
feature on a per-MN and per-subscription basis.
The MIP6-Feature-Vector AVP is also used on the LMA-to-HAAA
interface. Using the capability announcement AVP it is possible to
perform a simple capability negotiation between the LMA and the HAAA.
Those capabilities that are announced by both parties are also known
to be mutually supported. The capabilities listed in earlier are
also supported in the LMA-to-HAAA interface. The LMA-to-HAAA
interface does not define any new capability values.
5.6. Mobile-Node-Identifier AVP
The Mobile-Node-Identifier AVP (AVP Code 506) is of type UTF8String
and contains the mobile node identifier (MN-Identifier; see
[RFC5213]) in the NAI [RFC4282] format. This AVP is used on the MAG-
to-HAAA interface. The Mobile-Node-Identifier AVP is designed for
deployments where the MAG does not have a way to find out such MN
identity that could be used in subsequent PBU/PBA exchanges (e.g.,
due to identity hiding during the network access authentication) or
the HAAA wants to assign periodically changing identities to the MN.
The Mobile-Node-Identifier AVP is returned in the answer message that
ends a successful authentication (and possibly an authorization)
exchange between the MAG and the HAAA, assuming the HAAA is also able
to provide the MAG with the MN-Identifier in the first place. The
MAG MUST use the received MN-Identifier, if it has not been able to
get the mobile node identifier through other means. If the MAG
already has a valid mobile node identifier, then the MAG MUST
silently discard the received MN-Identifier.
5.7. Calling-Station-Id AVP
The Calling-Station-Id AVP (AVP Code 31) is of type UTF8String and
contains a link-layer identifier of the MN. This identifier
corresponds to the link-layer identifier as defined in RFC 5213,
Sections 2.2 and 8.6. The Link-Layer Identifier is encoded in ASCII
format (upper case only), with octet values separated by a "-".
Example: "00-23-32-C9-79-38". The encoding is actually the same as
the MAC address encoding in Section 3.21 of RFC 3580.
5.8. Service-Selection AVP
The Service-Selection AVP (AVP Code 493) is of type UTF8String and
contains an LMA-provided service identifier on the LMA-to-HAAA
interface. This AVP is re-used from [RFC5778]. The service
identifier may be used to assist the PBU authorization and the
assignment of the MN-HNP and the IPv4-MN-HoA as described in RFC 5149
[RFC5149]. The identifier MUST be unique within the PMIPv6 Domain.
In the absence of the Service-Selection AVP in the request message,
the HAAA may want to inform the LMA of the default service
provisioned to the MN and include the Service-Selection AVP in the
response message.
It is also possible that the MAG receives the service selection
information from the MN, for example, via some lower layer mechanism.
In this case, the MAG MUST include the Service-Selection AVP also in
the MAG-to-HAAA request messages. In the absence of the Service-
Selection AVP in the MAG-to-HAAA request messages, the HAAA may want
to inform the MAG of the default service provisioned to the MN and
include the Service-Selection AVP in the response message.
Whenever the Service-Selection AVP is included either in a request
message or in a response message, and the AAA interaction with HAAA
completes successfully, it is an indication that the HAAA also
authorized the MN to some service. This should be taken into account
when considering what to include in the Auth-Request-Type AVP.
The service selection concept supports signaling one service at time.
However, the MN policy profile MAY support multiple services being
used simultaneously. For this purpose, the HAAA MAY return multiple
LMA and service pairs (see Section 5.9) to the MAG in a response
message that ends a successful authentication (and possibly an
authorization) exchange between the MAG and the HAAA. Whenever the
MN initiates an additional mobility session to another service (using
a link layer or deployment specific method), the provisioned service
information is already contained in the MAG. Therefore, there is no
need for additional AAA signaling between the MAG and the HAAA.
5.9. Service-Configuration AVP
The Service-Configuration AVP (AVP Code 507) is of type Grouped and
contains a service and an LMA pair. The HAAA can use this AVP to
inform the MAG of the MN's subscribed services and LMAs where those
services are hosted in.
Service-Configuration ::= < AVP-Header: 507 >
[ MIP6-Agent-Info ]
[ Service-Selection ]
* [ AVP ]
6. Proxy Mobile IPv6 Session Management
Concerning a PMIPv6 mobility session, the HAAA, the MAG, and the LMA
Diameter entities SHOULD be stateful and maintain the corresponding
Authorization Session State Machine defined in [RFC3588]. If a state
is maintained, then a PMIPv6 mobility session that can be identified
by any of the Binding Cache Entry (BCE) Lookup Keys described in RFC
5213 (see Sections 5.4.1.1, 5.4.1.2, and 5.4.1.3) MUST map to a
single Diameter Session-Id. If the PMIPv6 Domain allows further
separation of sessions, for example, identified by the RFC 5213 BCE
Lookup Keys and the service selection combination (see Section 5.8
and [RFC5149]), then a single Diameter Session-Id MUST map to a
PMIPv6 mobility session identified by the RFC 5213 BCE Lookup Keys
and the selected service.
If both the MAG-to-HAAA and the LMA-to-HAAA interfaces are deployed
in a PMIPv6 Domain, and a state is maintained on both interfaces,
then one PMIPv6 mobility session would have two distinct Diameter
sessions on the HAAA. The HAAA needs to be aware of this deployment
possibility and SHOULD allow multiple Diameter sessions for the same
PMIPv6 mobility session.
Diameter session termination-related commands described in the
following sections may be exchanged between the LMA and the HAAA, or
between the MAG and the HAAA. The actual PMIPv6 session termination
procedures take place at the PMIPv6 protocol level and are described
in more detail in RFC 5213 and [MEXT-BINDING].
6.1. Session-Termination-Request
The LMA or the MAG MAY send the Session-Termination-Request (STR)
command [RFC3588] to inform the HAAA that the termination of an
ongoing PMIPv6 session is in progress.
6.2. Session-Termination-Answer
The Session-Termination-Answer (STA) [RFC3588] is sent by the HAAA to
acknowledge the termination of a PMIPv6 session.
6.3. Abort-Session-Request
The HAAA MAY send the Abort-Session-Request (ASR) command [RFC3588]
to the LMA or to the MAG and request termination of a PMIPv6 session.
6.4. Abort-Session-Answer
The Abort-Session-Answer (ASA) command [RFC3588] is sent by the LMA
or the MAG to acknowledge the termination of a PMIPv6 session.
7. Attribute Value Pair Occurrence Tables
The following tables list the PMIPv6 MAG-to-HAAA interface and LMA-
to-HAAA interface AVPs including those that are defined in [RFC5447].
Figure 2 contains the AVPs and their occurrences on the MAG-to-HAAA
interface. The AVPs that are part of grouped AVP are not listed in
the table; rather, only the grouped AVP is listed.
7.1. MAG-to-HAAA Interface
+---------------+
| Command-Code |
|-------+-------+
Attribute Name | REQ | ANS |
-------------------------------+-------+-------+
PMIP6-DHCP-Server-Address | 0 | 0+ |
MIP6-Agent-Info | 0+ | 0+ |
MIP6-Feature-Vector | 0-1 | 0-1 |
Mobile-Node-Identifier | 0-1 | 0-1 |
Calling-Station-Id | 0-1 | 0 |
Service-Selection | 0-1 | 0 |
Service-Configuration | 0 | 0+ |
+-------+-------+
Figure 2: MAG-to-HAAA Interface Generic Diameter Request
and Answer Commands AVPs
7.2. LMA-to-HAAA Interface
+---------------+
| Command-Code |
|-------+-------+
Attribute Name | REQ | ANS |
-------------------------------+-------+-------+
MIP6-Agent-Info | 0-1 | 0-1 |
MIP6-Feature-Vector | 0-1 | 0-1 |
Calling-Station-Id | 0-1 | 0 |
Service-Selection | 0-1 | 0-1 |
User-Name | 0-1 | 0-1 |
+-------+-------+
Figure 3: LMA-to-HAAA Interface Generic Diameter Request
and Answer Commands AVPs
8. Example Signaling Flows
Figure 4 shows a signaling flow example during PMIPv6 bootstrapping
using the AAA interactions defined in this specification. In step
(1) of this example, the MN is authenticated to the PMIPv6 Domain
using EAP-based authentication. The MAG to the HAAA signaling uses
the Diameter EAP Application. During step (2), the LMA uses the
Diameter NASREQ application to authorize the MN with the HAAA server.
The MAG-to-HAAA AVPs, as listed in Section 7.1, are used during step
(1). These AVPs are included only in the Diameter EAP Request (DER)
message which starts the EAP exchange and in the corresponding
Diameter EAP Answer (DEA) message which successfully completes this
EAP exchange. The LMA-to-HAAA AVPs, as listed in Section 7.2, are
used during step (2). Step (2) is used to authorize the MN request
for the mobility service and update the HAAA server with the assigned
LMA information. In addition, this step may be used to dynamically
assist in the assignment of the MN-HNP.
MN MAG/NAS LMA HAAA
| | | |
| L2 attach | | |
|-------------------->| | |
| EAP/req-identity | | |
|<--------------------| | |
| EAP/res-identity | DER + MAG-to-HAAA AVPs | s
|-------------------->|---------------------------------------->| t
| EAP/req #1 | DEA (EAP request #1) | e
|<--------------------|<----------------------------------------| p
| EAP/res #2 | DER (EAP response #2) |
|-------------------->|---------------------------------------->| 1
: : : :
: : : :
| EAP/res #N | DER (EAP response #N) |
|-------------------->|---------------------------------------->|
| EAP/success | DEA (EAP success) + MAG-to-HAAA AVPs |
|<--------------------|<----------------------------------------|
: : : :
: : : :
| | PMIPv6 PBU | AAR + | s
| |------------------->| LMA-to-HAAA AVPs | t
| | |------------------->| e
| | | AAA + | p
| | | LMA-to-HAAA AVPs |
| | PMIPv6 PBA |<-------------------| 2
| RA |<-------------------| |
|<--------------------| | |
: : : :
: : : :
| IP connectivity | PMIPv6 tunnel up | |
|---------------------|====================| |
| | | |
Figure 4: MAG and LMA Signaling Interaction with AAA Server
during PMIPv6 Bootstrapping
9. IANA Considerations
9.1. Attribute Value Pair Codes
This specification defines the following new AVPs:
PMIP6-DHCP-Server-Address 504
PMIP6-IPv4-Home-Address 505
Mobile-Node-Identifier 506
Service-Configuration 507
9.2. Namespaces
This specification defines new values to the Mobility Capability
registry (see [RFC5447]) for use with the MIP6-Feature-Vector AVP:
Token | Value | Description
---------------------------------+----------------------+------------
PMIP6_SUPPORTED | 0x0000010000000000 | [RFC5779]
IP4_HOA_SUPPORTED | 0x0000020000000000 | [RFC5779]
LOCAL_MAG_ROUTING_SUPPORTED | 0x0000040000000000 | [RFC5779]
10. Security Considerations
The security considerations of the Diameter Base protocol [RFC3588],
Diameter EAP application [RFC4072], Diameter NASREQ application
[RFC4005], and Diameter Mobile IPv6 integrated scenario bootstrapping
[RFC5447] are applicable to this document.
In general, the Diameter messages may be transported between the LMA
and the Diameter server via one or more AAA brokers or Diameter
agents. In this case, the LMA to the Diameter server AAA
communication rely on the security properties of the intermediate AAA
brokers and Diameter agents (such as proxies).
11. Acknowledgements
Jouni Korhonen would like to thank the TEKES GIGA program MERCoNe-
project for providing funding to work on this document while he was
with TeliaSonera. The authors also thank Pasi Eronen, Peter McCann,
Spencer Dawkins, and Marco Liebsch for their detailed reviews of this
document.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
J. Arkko, "Diameter Base Protocol", RFC 3588,
September 2003.
[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application",
RFC 4005, August 2005.
[RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter
Extensible Authentication Protocol (EAP)
Application", RFC 4072, August 2005.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen,
"The Network Access Identifier", RFC 4282,
December 2005.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, August 2008.
[RFC5447] Korhonen, J., Bournelle, J., Tschofenig, H., Perkins,
C., and K. Chowdhury, "Diameter Mobile IPv6: Support
for Network Access Server to Diameter Server
Interaction", RFC 5447, February 2009.
[RFC5778] Korhonen, J., Ed., Tschofenig, H., Bournelle, J.,
Giaretta, G., and M. Nakhjiri, "Diameter Mobile IPv6:
Support for Home Agent to Diameter Server
Interaction", RFC 5778, February 2010.
12.2. Informative References
[MEXT-BINDING] Muhanna, A., Khalil, M., Gundavelli, S., Chowdhury,
K., and P. Yegani, "Binding Revocation for IPv6
Mobility", Work in Progress, October 2009.
[NETLMM-LMA] Korhonen, J. and V. Devarapalli, "LMA Discovery for
Proxy Mobile IPv6", Work in Progress, September 2009.
[NETLMM-PMIP6] Wakikawa, R. and S. Gundavelli, "IPv4 Support for
Proxy Mobile IPv6", Work in Progress, September 2009.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, 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.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J.,
and H. Levkowetz, "Extensible Authentication Protocol
(EAP)", RFC 3748, June 2004.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility
Support in IPv6", RFC 3775, June 2004.
[RFC4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
Chowdhury, "Mobile Node Identifier Option for Mobile
IPv6 (MIPv6)", RFC 4283, November 2005.
[RFC5149] Korhonen, J., Nilsson, U., and V. Devarapalli,
"Service Selection for Mobile IPv6", RFC 5149,
February 2008.
Authors' Addresses
Jouni Korhonen (editor)
Nokia Siemens Network
Linnoitustie 6
Espoo FI-02600
Finland
EMail: jouni.nospam@gmail.com
Julien Bournelle
Orange Labs
38-4O rue du general Leclerc
Issy-Les-Moulineaux 92794
France
EMail: julien.bournelle@orange-ftgroup.com
Kuntal Chowdhury
Cisco Systems
30 International Place
Tewksbury, MA 01876
USA
EMail: kchowdhury@cisco.com
Ahmad Muhanna
Ericsson, Inc.
2201 Lakeside Blvd.
Richardson, TX 75082
USA
EMail: Ahmad.muhanna@ericsson.com
Ulrike Meyer
RWTH Aachen
EMail: meyer@umic.rwth-aachen.de
ISO Plain Language
On this page
§1Introduction
RFC 5779 defines the Authentication, Authorization, and Accounting (AAA) interactions between a Mobile Access Gateway (MAG) and a AAA server, and between a Local Mobility Anchor (LMA) and a AAA server, inside a Proxy Mobile IPv6 (PMIPv6) domain. These interactions are primarily used to download and update mobile node specific policy profile information between the PMIPv6 entities and a remote policy store.
Downloading a policy profile to the gateway from a remote store is useful because it eases deployment and network maintenance in larger PMIPv6 domains. The same AAA infrastructure that authenticates and authorizes the mobile node for network access can be reused to fetch some or all of the policy profile the gateway needs.
After the network has authenticated the mobile node, the MAG sends a Proxy Binding Update (PBU) to the LMA to set up a mobility session on behalf of the mobile node. When the LMA receives the PBU, it may need to authorize that PBU against the AAA infrastructure. The same infrastructure is also used to update the remote policy store with mobility session information the LMA holds.
In this specification the home AAA server, called the HAAA, is co-located with the remote policy store. The Network Access Server (NAS) function may be co-located with the MAG function inside the network access router. Diameter, specified in RFC 3588, is the AAA protocol used.
This RFC defines how a mobile device's gateway and mobility anchor talk to a central server over Diameter, the protocol used for sign-in and accounting. The main job is fetching the rules that apply to one device.
§3The PMIPv6 Domain and Its Entities
A PMIPv6 domain has three kinds of entity. The Mobile Access Gateway sits at the edge of the access network and is the point where the mobile node attaches. The Local Mobility Anchor is the entity that holds the mobile node's home address and serves as the routing anchor for its traffic. The home AAA server holds the subscriber's records and, in this specification, also acts as the remote policy store.
Two separate Diameter interfaces connect the domain to the HAAA. The MAG-to-HAAA interface, marked (1) in the RFC's Figure 1, runs between each gateway and the HAAA. The LMA-to-HAAA interface, marked (2), runs between the anchor and the HAAA. The gateway reaches the anchor over an IPv4 or IPv6 network, and two tunnels, Tunnel1 and Tunnel2, carry the mobile node's traffic between the gateway and the anchor.
When a mobile node attaches, a network access authentication procedure usually starts. The choice of mechanism depends on the access network, and may be based on the Extensible Authentication Protocol (EAP). During that procedure the MAG, acting as a NAS, queries the HAAA using Diameter. If the HAAA finds that the subscriber is also authorized for the PMIPv6 service, PMIPv6 specific information is returned along with the successful authentication answer.
After the mobile node has been authenticated, the MAG sends a PBU to the LMA based on the node's policy profile information. On receiving the PBU, the LMA interacts with the HAAA and fetches the relevant parts of the subscriber policy profile and the authorization information related to the mobility service session.
Three parts take part: the gateway where the device connects, the anchor that holds its address, and a central server that holds the subscriber's records. The gateway and the anchor each open their own Diameter connection to that server, and the device's traffic travels between the gateway and the anchor over a pair of tunnels.
- L2 attachThe device reaches the access network.
- EAP/req-identityThe gateway asks the device for its identity.
- DER + MAG-to-HAAA AVPsThe gateway starts the EAP exchange with the home server.
- DEA (EAP success) + MAG-to-HAAA AVPsThe server confirms the exchange and returns the policy profile.
- PMIPv6 PBUThe gateway asks the anchor to set up the mobility session.
- AAR + LMA-to-HAAA AVPsThe anchor asks the home server to authorize the request.
- AAA + LMA-to-HAAA AVPsThe server authorizes the session and returns the assigned address.
- PMIPv6 PBAThe anchor confirms the binding to the gateway.
- RAThe gateway sends the router advertisement to the device.
§4.1The MAG-to-HAAA Interface
The MAG-to-HAAA interactions bootstrap the PMIPv6 mobility session when a mobile node attaches to a PMIPv6 domain and authenticates to it. The interface may also be used for accounting. The MAG acts as a Diameter client on this interface.
This specification defines no new Application-IDs or Command Codes for either Diameter connection. It is generic to any Diameter application and its commands that suits network access authentication and authorization, for example NASREQ from RFC 4005 and EAP from RFC 4072.
Whenever the MAG sends a Diameter request to the HAAA, the User-Name attribute value pair should carry the mobile node's identity, unless the identity is being suppressed for policy reasons, such as when identity hiding is in effect. The identity, when available, must be in Network Access Identifier (NAI) format. At minimum, the home realm of the mobile node must be available at the MAG when network access authentication takes place, because without it the MAG cannot route the Diameter request messages towards the correct HAAA.
The identity used on this interface may be entirely related to the network access authentication, and therefore not suitable as the mobile node identifier mobility option value in the later PBU and Proxy Binding Acknowledgement (PBA) messages. For session management and service authorization, session state should be maintained on the MAG-to-HAAA interface.
When a device connects, the gateway signs it in with the home server over Diameter. The gateway puts the device's name in the User-Name field so the server knows which subscriber record to look up, and it needs the device's home realm to find that server in the first place.
§4.2The LMA-to-HAAA Interface
The LMA-to-HAAA interface has several uses: authorizing the incoming PBU, updating the LMA address at the HAAA, delegating assignment of the mobile node's home network prefix (MN-HNP) or IPv4 home address (IPv4-MN-HoA) to the HAAA, and handling accounting and PMIPv6 session management. Its primary purpose is to update the HAAA with the LMA address information in case of a dynamically assigned LMA, and to exchange mobile node address assignment information between the LMA and the HAAA.
Whenever the LMA sends a Diameter request, the User-Name attribute should carry the mobile node's identity, and that identity is strongly recommended to be the same as the mobile node identifier in the PBU mobility option. It should also match the identity used on the MAG-to-HAAA interface; where the two differ, the HAAA must have a mechanism to map one to the other. If the PBU carries a link-layer identifier, the Calling-Station-Id attribute should be included. If the PBU carries a service selection mobility option, the Service-Selection attribute should be included.
The Auth-Request-Type attribute must be set to AUTHORIZE_ONLY. If the HAAA cannot authorize the subscriber's mobility service session, the reply to the LMA must set the Result-Code attribute to DIAMETER_AUTHORIZATION_REJECTED (5003), which indicates a permanent failure. The failed authorization results in a rejected PBU, and a PBA with an appropriate error Status Value is sent back to the MAG.
Authorization must be performed at least for the initial PBU that sets up a mobility session. For later re-registration and handover PBUs the step may be repeated, in which case the interface should also maintain an authorization session state.
For address management, the LMA and the HAAA use the MIP6-Home-Link-Prefix attribute to exchange the MN-HNP and the PMIP6-IPv4-Home-Address attribute to exchange the IPv4-MN-HoA. Both sit inside the MIP6-Agent-Info attribute. Which entity owns address management is deployment specific and must be agreed per deployment. When the LMA owns it, the MIP6-Agent-Info attribute tells the HAAA which prefix or address was assigned. When the LMA delegates it to the HAAA, the request carries undefined addresses, that is 0::0 and 0.0.0.0, and the LMA expects the assigned values back in the answer.
The specification defines no HAAA-initiated LMA relocation. So when the MIP6-Agent-Info attribute appears in an answer from the HAAA to the LMA, the HAAA signals this by setting the MIP-Home-Agent-Address to the all zeroes address, for example 0::0, and leaving out the MIP-Home-Agent-Host attribute.
After the gateway asks the anchor to set up a session, the anchor asks the home server whether the device is allowed to have one. If the server says no, the request is refused with the error code 5003 and the gateway is told to fail the session. The same exchange is where the anchor tells the server which address it uses and which address the device was given.
§5Attribute Value Pairs
Diameter carries information in attribute value pairs (AVPs). This section describes the AVPs this specification defines and the way it reuses existing ones in a PMIPv6 specific way. The MIP6-Agent-Info grouped AVP, code 486, defined in RFC 5447, carries the LMA addressing information and the MN-HNP. This specification extends it with the PMIP6-IPv4-Home-Address AVP, using the Diameter extensibility rules. The extended grouping has this form:
MIP6-Agent-Info ::= < AVP-Header: 486 > *2[ MIP-Home-Agent-Address ] [ MIP-Home-Agent-Host ] [ MIP6-Home-Link-Prefix ] [ PMIP6-IPv4-Home-Address ] * [ AVP ]If the MIP-Home-Agent-Address is set to the all zeroes address, the receiver must ignore that attribute.
The PMIP6-IPv4-Home-Address AVP, code 505, is of type Address and holds an IPv4 address. It carries the IPv4-MN-HoA from the HAAA to the MAG and should only be present when the mobile node is statically provisioned with that address, because proactive dynamic assignment may reserve IPv4 address resources the node never uses. The MIP6-Home-Link-Prefix AVP, code 125, carries the MN-HNP; the low 64 bits of the prefix must be all zeroes. The PMIP6-DHCP-Server-Address AVP, code 504, holds the IP address of the DHCP server assigned to the gateway serving the newly attached mobile node, with the Address type matching whether it is a DHCPv4 or a DHCPv6 server address.
The Mobile-Node-Identifier AVP, code 506, is of type UTF8String and holds the mobile node identifier in NAI format. It is used on the MAG-to-HAAA interface for deployments where the gateway cannot find such an identity by other means, for example because of identity hiding, or where the HAAA wants to assign periodically changing identities. The gateway must use the received identifier if it has not obtained one by other means, and must silently discard it if it already holds a valid identifier.
The Calling-Station-Id AVP, code 31, holds a link-layer identifier of the mobile node, encoded in ASCII in upper case only with octet values separated by a hyphen, for example 00-23-32-C9-79-38. The Service-Selection AVP, code 493, holds a service identifier and is re-used from RFC 5778; the identifier must be unique within the PMIPv6 domain. The Service-Configuration AVP, code 507, is of type Grouped and carries a service and an LMA pair, so the HAAA can tell the gateway which services the node subscribes to and which LMAs host them.
The MIP6-Feature-Vector AVP, originally defined in RFC 5447, carries capability flags. This document adds three bits: PMIP6_SUPPORTED, which says the gateway supports PMIPv6 and which the HAAA mirrors back to say it supports PMIPv6 too; IP4_HOA_SUPPORTED, which says the gateway can act as a minimal DHCP server and relay and deliver an IPv4 home address to the node; and LOCAL_MAG_ROUTING_SUPPORTED, which says the gateway can route packets directly between mobile nodes anchored to the same gateway, without reverse tunnelling through the LMA. When the HAAA clears a bit in the returned vector, it is withholding that permission.
Each piece of information in the exchange has a named field, called an attribute value pair, with a numeric code. The codes below are the ones this RFC adds. The feature vector is the part that carries permissions: each bit says the sender supports one feature, and the server can clear a bit to say no.
- 504PMIP6-DHCP-Server-Address — The IP address of the DHCP server assigned to the gateway serving the newly attached mobile node.
- 505PMIP6-IPv4-Home-Address — The IPv4 home address of the mobile node.
- 506Mobile-Node-Identifier — The mobile node identifier in NAI format.
- 507Service-Configuration — A grouped attribute holding a service and the LMA that hosts it.
- 0x0000010000000000PMIP6_SUPPORTED — The gateway supports PMIPv6; the server echoes the bit to say it does too.
- 0x0000020000000000IP4_HOA_SUPPORTED — The gateway can deliver an IPv4 home address to the mobile node.
- 0x0000040000000000LOCAL_MAG_ROUTING_SUPPORTED — The gateway can route packets directly between mobile nodes anchored to it.
§6Session Management
For a PMIPv6 mobility session, the HAAA, the MAG and the LMA Diameter entities should be stateful and maintain the Authorization Session State Machine defined in RFC 3588. When state is maintained, a PMIPv6 mobility session identified by any of the Binding Cache Entry lookup keys described in RFC 5213 must map to a single Diameter Session-Id. If the domain separates sessions further, for example by combining the lookup keys with the service selection, then a single Diameter Session-Id must map to the PMIPv6 mobility session identified by the lookup keys and the selected service.
When both the MAG-to-HAAA and the LMA-to-HAAA interfaces are deployed and state is maintained on both, one PMIPv6 mobility session has two distinct Diameter sessions at the HAAA. The HAAA needs to be aware of this deployment possibility and should allow multiple Diameter sessions for the same PMIPv6 mobility session.
Four commands handle the end of a session, all taken from RFC 3588. The LMA or the MAG may send a Session-Termination-Request to say that the termination of an ongoing PMIPv6 session is in progress. The HAAA answers with a Session-Termination-Answer. The HAAA may send an Abort-Session-Request to the LMA or the MAG to request termination of a PMIPv6 session, and the LMA or the MAG replies with an Abort-Session-Answer. The actual PMIPv6 session termination procedures take place at the PMIPv6 protocol level and are described in RFC 5213.
The server, the gateway and the anchor each keep track of the sessions they are part of, and each session gets a Diameter session identifier. Because a session spans two links, the server may end up holding two Diameter sessions for one mobility session, and it has to allow that. Four commands tell the server a session is ending or ask it to end one.
§10Security Considerations
The RFC applies the security considerations of the Diameter Base protocol in RFC 3588, the Diameter EAP application in RFC 4072, the Diameter NASREQ application in RFC 4005, and the Diameter Mobile IPv6 integrated scenario bootstrapping in RFC 5447.
In general, Diameter messages may travel between the LMA and the Diameter server through one or more AAA brokers or Diameter agents. In that case the LMA's communication with the Diameter server relies on the security properties of those intermediate brokers and agents, such as proxies.
This RFC adds no security mechanism of its own. It inherits the security rules of the Diameter protocols it uses, and it notes that when a broker or proxy sits between the anchor and the server, the security of that link depends on the broker.