Diameter Support for Proxy Mobile IPv6 Localized Routing

Proxy Mobile IPv6 (PMIPv6) allows the Mobile Access Gateway (MAG) to optimize media delivery by locally routing packets from a Mobile Node (MN) to a Correspondent Node (CN) that is locally attached to an access link connected to the same Mobile Access Gateway, avoiding tunneling them to the Mobile Node's Local Mobility Anchor (LMA). This is referred to as "local routing" in RFC 5213 . However, this mechanism is not applicable to the typical scenarios in which the MN and CN are connected to different MAGs and are registered to the same LMA or different LMAs. takes those typical scenarios into account and defines the problem statement for PMIPv6 localized routing. Based on the scenarios A11, A12, and A21 described in , specifies the PMIPv6 localized routing protocol that is used to establish a localized routing path between two Mobile Access Gateways in a PMIPv6 domain. This document describes Authentication, Authorization, and Accounting (AAA) support using Diameter for the authorization procedure between the PMIPv6 mobility entities (MAG or LMA) and a AAA server within a Proxy Mobile IPv6 domain for localized routing in the scenarios A11, A12, and A21 described in .

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 .

This document addresses how to provide authorization information to the Mobile Node's MAG or LMA to enable localized routing and resolve the destination MN's MAG by means of interaction between the LMA and the AAA server. shows the reference architecture for Localized Routing Service Authorization. This reference architecture assumes that If the MN and CN belong to different LMAs, the MN and CN should share the same MAG (i.e., scenario A12 described in ), e.g., MN1 and CN2 in are attached to MAG1 and belong to LMA1 and LMA2, respectively. Note that LMA1 and LMA2 in are in the same provider domain (as described in ). If the MN and CN are attached to different MAGs, the MN and CN should belong to the same LMA (i.e., scenario A21 described in ); for example, MN1 and CN3 in Figure 1 are attached to MAG1 and MAG3, respectively, but belong to LMA1. The MN and CN may belong to the same LMA and may be attached to the same MAG (i.e., scenario A11 described in ), e.g., MN1 and CN1 in are both attached to the MAG1 and belong to LMA1. The MAG and LMA support Diameter client functionality.

+---------+ +---------------------->| AAA & | | +------>| Policy | | | | Profile | | Diameter +---------+ | | | +--V-+ +----+ | +------->|LMA1| |LMA2| | | +---++ +----+ | | | | | Diameter | | +-------+--------- | | | | | | PMIP | | \\ | | // // \\ | | // // \\ | | // // \\ | | | | | | +---->+---------------+ +----+ | | MAG1 | |MAG3| +-------->+---------------+ +----+ : : : : +---+ +---+ +---+ +---+ |MN1| |CN1| |CN2| |CN3| +---+ +---+ +---+ +---+ The interaction of the MAG and LMA with the AAA server according to the extension specified in this document is used to authorize the localized routing service.

This section describes Attribute Value Pairs (AVPs) and AVP values defined by this specification or reused from existing specifications in a PMIPv6-specific way.

The User-Name AVP (AVP Code 1) is defined in , Section 8.14. This AVP is used to carry the Mobile Node identifier (MN-Identifier) in the Diameter AA-Request message sent to the AAA server. The MN-Identifier is defined in PMIPv6 .

The PMIP6-IPv4-Home-Address AVP (AVP Code 505) is defined in , Section 5.2. This AVP is used to carry the Mobile Node's IPv4 home address (IPv4-MN-HoA) in the Diameter AA-Request message sent to the AAA server. The IPv4-MN-HoA is defined in .

The MIP6-Home-Link-Prefix AVP (AVP Code 125) is defined in , Section 5.3. This AVP is used to carry the Mobile Node's home network prefix (MN-HNP) in the Diameter AA-Request sent to the AAA server.

The MIP6-Feature-Vector AVP is defined in and contains a 64-bit flags field used to indicate supported capabilities to the AAA server. This document allocates a new capability flag bit according to the IANA rules in RFC 5447 . INTER_MAG_ROUTING_SUPPORTED (0x0002000000000000) When set, this flag indicates support or authorization of Direct routing of IP packets between MNs anchored to different MAGs without involving any LMA. During the network access authentication and authorization procedure , this flag is set by the MAG or LMA in the MIP6-Feature-Vector AVP included in the request to indicate to the home AAA server (HAAA) that inter-MAG direct routing may be provided to the mobile node identified by the User-Name AVP. By setting the INTER_MAG_ROUTING_SUPPORTED flag in the response, the HAAA indicates to the MAG or LMA that direct routing of IP packets between this mobile node and another node anchored to a different MAG is authorized. The MAG and the LMA set also the INTER_MAG_ROUTING_SUPPORTED flag of the MIP6-Feature-Vector AVP in AA-R sent to the HAAA for requesting authorization of inter-MAG direct routing between the mobile nodes identified in the request by two distinct instances of the User-Name AVP. If this bit is set in the returned MIP6-Feature-Vector AVP, the HAAA authorizes direct routing of packets between MNs anchored to different MAGs. When the INTER_MAG_ROUTING_SUPPORTED flag is cleared, either in request or response, it indicates that the procedures related to authorization of localized routing between MNs anchored to different MAGs is not supported or not authorized. MAG and LMA compliant to this specification MUST support this policy feature on a per-MN and per-subscription basis.

Localized Routing Service Authorization can happen during the network access authentication procedure before localized routing is initialized. In this case, the preauthorized pairs of LMA / prefix sets can be downloaded to Proxy Mobile IPv6 entities during the procedure from . Localized routing can be initiated once the destination of a received packet matches one or more of the prefixes received during the procedure from . shows an example scenario in which MAG1 acts as a Diameter client, processing the data packet from MN1 to MN2 and requesting authorization of localized routing (i.e., MAG-Initiated LR authorization). In this example scenario, MN1 and MN2 are attached to the same MAG and anchored to the different LMAs (i.e., scenario A12 described in ). In this case, MAG1 knows that MN2 belongs to a different LMA (which can be determined by looking up the binding cache entries corresponding to MN1 and MN2 and comparing the addresses of LMA1 and LMA2). In order to set up a localized routing path with MAG2, MAG1 acts as Diameter client and sends an AA-Request message to the AAA server. The message contains an instance of the MIP6-Feature-Vector (MFV) AVP with the LOCAL_MAG_ROUTING_SUPPORTED bit (, Section 5.5) set, two instances of the User-Name AVP containing the identifiers of MN1 and MN2. In addition, the message may contain either: - an instance of the MIP6-Home-Link-Prefix AVP carrying the MN1's IPv4 address; - an instance of the PMIP6-IPv4-Home-Address AVP carrying the MN1's home network prefix (MN-HNP). The AAA server authorizes the localized routing service by checking if MN1 and MN2 are allowed to use localized routing. If so, the AAA server responds with a AAA message encapsulating an instance of the MIP6-Feature-Vector (MFV) AVP with the LOCAL_MAG_ROUTING_SUPPORTED bit (, Section 5.5) set indicating that direct routing of IP packets between MNs anchored to the same MAG is authorized. MAG1 then knows that the localized routing between MN1 and MN2 is allowed. Then, MAG1 sends the Request messages respectively to LMA1 and LMA2. The request message is the Localized Routing Initialization (LRI) message in Figure 2 and belongs to the Initial phase of the localized routing. LMA1 and LMA2 respond to MAG1 using the Localized Routing Acknowledge message (LRA in ) in accordance with . In case of LRA_WAIT_TIME expiration , MAG1 should ask for authorization of localized routing again according to the procedure described above before the LRI is retransmitted up to a maximum of LRI_RETRIES.

+---+ +---+ +----+ +----+ +---+ +----+ |MN2| |MN1| |MAG1| |LMA1| |AAA| |LMA2| +-|-+ +-+-+ +-+--+ +-+--+ +-+-+ +-+--+ | | Anchored | | | o-----------------------------------------------o | | Anchored | | | | o------------------o | | | Data[MN1->MN2] | | | | |------->| | | | | | | AA-Request(MFV, MN1,MN2) | | | |--------------------> | | | | | AA-Answer(MFV) | | | | |<-------------------- | | | | | LRI | | | | | |-------->| | | | | | | LRI | | | | |----------------------------->| | | | LRA | | | | | |<--------| | | | | | | LRA | | | | |<-----------------------------| shows the second example scenario, in which LMA1 acts as a Diameter client, processing the data packet from MN2 to MN1 and requesting the authorization of localized routing. In this scenario, MN1 and MN2 are attached to a different MAG and anchored to the same LMA (i.e., A21 described in ), LMA knows that MN1 and MN2 belong to the same LMA (which can be determined by looking up the binding cache entries corresponding to MN1 and MN2 and comparing the addresses of the LMA corresponding to MN1 and LMA corresponding to MN2). In contrast with the signaling flow shown in , it is LMA1 instead of MAG1 that initiates the setup of the localized routing path. The Diameter client in LMA1 sends an AA-Request message to the AAA server. The message contains an instance of the MIP6-Feature-Vector (MFV) AVP with the INTER_MAG_ROUTING_SUPPORTED bit (Section 4.5) set indicating direct routing of IP packets between MNs anchored to different MAGs is supported and two instances of the User-Name AVP containing identifiers of MN1 and MN2. The AAA server authorizes the localized routing service by checking if MN1 and MN2 are allowed to use localized routing. If so, the AAA server responds with an AA-Answer message encapsulating an instance of the MIP6-Feature-Vector (MFV) AVP with the INTER_MAG_ROUTING_SUPPORTED bit (Section 4.5) set indicating that direct routing of IP packets between MNs anchored to different MAGs is authorized. LMA1 then knows the localized routing is allowed. In a successful case, LMA1 responds to MAG1 in accordance with . In the case of LRA_WAIT_TIME expiration , LMA1 should ask for authorization of localized routing again according to the procedure described above before the LRI is retransmitted up to a maximum of LRI_RETRIES.

+---+ +----+ +----+ +---+ +----+ +---+ |MN1| |MAG1| |LMA1| |AAA| |MAG2| |MN2| +-+-+ +-+--+ +-+--+ +-+-+ +-+--+ +-+-+ | | | Anchored | | | Anchored o-------------------+--------o o--------+-------o Data[MN2->MN1] | | | | |<----- | | | | | |AA-Request(MFV,MN1,MN2) | | | |--------->| | | | | |AA-Answer(MFV) | | | | LRI |<---------| | | | |<------| LRI | | | | LRA |------------------>| | | |------>| LRA | | | | |<------------------| | shows another example scenario, in which LMA1 acts as a Diameter client, processing the data packet from MN2 to MN1 and requesting the authorization of localized routing. In this scenario, MN1 and MN2 are attached to the same MAG and anchored to the same LMA (i.e., A11 described in ), the LMA knows that MN1 and MN2 belong to the same LMA (which can be determined by looking up the binding cache entries corresponding to MN1 and MN2 and comparing the addresses of LMA corresponding to MN1 and LMA corresponding to MN2). The Diameter client in LMA1 sends an AA-Request message to the AAA server. The message contains an instance of the MIP6-Feature-Vector AVP with the LOCAL_MAG_ROUTING_SUPPORTED bit set and two instances of the User-Name AVP containing the identifiers MN1 and MN2. The AAA server authorizes the localized routing service by checking if MN1 and MN2 are allowed to use localized routing. If so, the AAA server responds with an AA-Answer message encapsulating an instance of the MIP6-Feature-Vector (MFV) AVP with the LOCAL_MAG_ROUTING_SUPPORTED bit (, Section 5.5) set indicating that direct routing of IP packets between MNs anchored to the same MAG is authorized. LMA1 then knows the localized routing is allowed and responds to MAG1 for localized routing in accordance with .In the case of LRA_WAIT_TIME expiration , LMA1 should ask for authorization of localized routing again according to the procedure described above before the LRI is retransmitted up to a maximum of LRI_RETRIES.

+---+ +---+ +----+ +----+ +---+ |MN2| |MN1| |MAG1| |LMA1| |AAA| +-+-+ +-+-+ +-+--+ +-+--+ +-|-+ | | Anchored | | o-----------------------o | | | Anchored | | | o--------+-------o Data[MN2->MN1] | | | |<----- | | | | |AA-Request(MFV,MN1,MN2) | | | |--------->| | | | |AA-Answer(MFV) | | | LRI |<---------| | | |<------| | | | | LRA | | | | |------>| |

The security considerations for the Diameter Network Access Server Requirements (NASREQ) and Diameter Proxy Mobile IPv6 applications are also applicable to this document. The service authorization solicited by the MAG or the LMA relies upon the existing trust relationship between the MAG/LMA and the AAA server. An authorized MAG could, in principle, track the movement of any participating mobile nodes at the level of the MAG to which they are anchored. If such a MAG were compromised, or under the control of a bad actor, then such tracking could represent a privacy breach for the set of tracked mobile nodes. In such a case, the traffic pattern from the compromised MAG might be notable, so monitoring for, e.g., excessive queries from MAGs, might be worthwhile.

This specification defines a new value in the "Mobility Capability Registry" for use with the MIP6-Feature-Vector AVP: INTER_MAG_ROUTING_SUPPORTED (see ).

Paulo Loureiro, Jinwei Xia and Yungui Wang all contributed to early versions of this document.

The authors would like to thank Lionel Morand, Marco Liebsch, Carlos Jesus Bernardos Cano, Dan Romascanu, Elwyn Davies, Basavaraj Patil, Ralph Droms, Stephen Farrel, Robert Sparks, Benoit Claise, and Abhay Roy for their valuable comments and suggestions on this document.