Scenarios of the usage of multiple home network prefixes on a logical interface
draft-hong-netext-scenario-logical-interface-02

Abstract

A logical interface is used to hide the existence and the change of physical interface from the IP layer of a host and it also can be used for a multiple interfaces mobile node in PMIPv6 domain. If a LMA assigns multiple home network prefixes to a multiple interfaces mobile node with a logical interface, there are various usages of multiple home network prefixes on the logical interface. As following general PMIPv6 operations described in RFC 5213, all multiple home network prefixes are shown to the IP layer. Also, the logical interface hides the existence of multiple home network prefixes and shows only one home network prefix to host IP layer. And in a LMA point of view, a LMA may acknowledge each physical interface or only logical interface of a mobile node when a multiple interfaces mobile node utilizes the logical interface. In this internet draft, we describe various scenarios of the usage of multiple home network prefixes on a logical interface.

Status of this Memo

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This Internet-Draft will expire on April 28, 2011.

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Table of Contents

1.  Introduction
2.  Requirements Language
3.  Multihoming support on a logical interface in PMIPv6
4.  The usage of multiple home network prefixes on a logical interface
    4.1.  Scenario 1 – LMA acknowledges each physical interface of a MN
    4.2.  Scenario 2 – LMA acknowledges logical interface of a MN
    4.3.  Scenario 3 – All home network prefixes are shown to IP host stack
    4.4.  Scenario 4 – Only one home network prefix is shown to IP host stack
5.  Security Considerations
6.  IANA Considerations
7.  References
    7.1.  Normative References
    7.2.  Informative References
§  Authors' Addresses

1.  Introduction

Proxy Mobile IPv6 (PMIPv6)[RFC5213] (Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, “Proxy Mobile IPv6,” August 2008.) is a network based IP mobility support protocol, which does not require any modifications to mobile nodes. PMIPv6 makes it possible to support mobility for IPv6 nodes without an involvement of mobile nodes. That is, on behalf of mobile nodes, a mobile access gateway (MAG) in the network performs the signaling for mobility management with a local mobility anchor (LMA).

Due to the simultaneous usage of multiple interfaces in a mobile node and the change of network interfaces, IETF netext working group has studied the hiding access technology changes from host IP layer. Link layer implementation such as "logical interface" can hide the actually used physical interfaces and the change of physical interfaces from the IP layer. Many operating systems offer support to the usage of logical interface over multiple physical interfaces without any big efforts. In another internet draft [I‑D.ietf‑netext‑logical‑interface‑support‑00] (Melia, T. and S. Gundavelli, “Logical Interface Support for multi-mode IP Hosts, draft-ietf-netext-logical-interface-support-00 (work in progress),” September 2010.), operations details of the logical interface are explained and it identifies the applicability of the usage of logical interface.

PMIPv6 specifications allow mobile nodes to connect PMIPv6 domain through multiple network interfaces for simultaneous access and a LMA may allocate more than one home network prefix for a given interface of the mobile node. In basic PMIPv6 specification, the multiple home network prefixes that the LMA allocates to a mobile node are shown totally to the host IP stack of the mobile node. Also, if a mobile node utilizes a logical interface to hide the change of network interfaces, we can extend the usage of a logical interface to hide the multiplicity of home network prefixes. So we can categorize the usage of a logical interface as two cases. First, as following general PMIPv6 operations described in RFC 5213, all multiple home network prefixes are shown to host IP layer. Second, for some reasons such as the session continuity, only one home network prefix is shown to the host IP stack of the mobile node even though the LMA allocates multiple home network prefixes. In second case, the logical interface does some necessary jobs to hide the existence of multiple interfaces and also the existence of multiple home network prefixes. And the logical interface does some necessary jobs when network interfaces are changed and/or home network prefixes are changed.

Although the primary purpose of a logical interface is to hide the access technology changes from host IP layer in a mobile node, the usage of a logical interface can influence the acknowledgement of interfaces of a mobile node in a LMA point of view. If a multiple interfaces mobile node utilizes a logical interface, we can consider both cases; a LMA may acknowledge each physical interface of a multiple interfaces mobile node; a LMA may acknowledge only a logical interface of a multiple interfaces mobile node.

2.  Requirements Language

In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL", "RECOMMENDED", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  Multihoming support on a logical interface in PMIPv6

In PMIPv6 specification, to provide multihoming support, it describes three key aspects as following.

• When a mobile node connects to a PMIPv6 domain through multiple interfaces for simultaneous access, the LMA MUST allocate a mobility session for each of the attached interfaces.
• The LMA MAY allocate more than one home network prefix for a given interface of the mobile node.
• The LMA MUST allow for a handoff between two different interfaces of a mobile node. In such a scenario, all the home network prefixes associated with one interface (part of one mobility session) will be associated with a different interface of the mobile node.

Even though a logical interface is adopted in a multiple interface mobile node in PMIPv6 domain, the above three aspects SHOULD be applied.

For the regarding of first aspect, if a logical interface is used in a multiple interfaces mobile node, even though multiple interfaces are used, the host IP stack of the mobile node only acknowledges the logical interface. But in a LMA point of view, a LMA can acknowledge each physical interface if link-layer identifier of each physical interface is delivered to a LMA through a PBU (Proxy Binding Update) message. Or a LMA can acknowledge only logical interface if link-layer identifier of logical interface is delivered to a LMA through PBU message. Section 4.1 and section 4.2 describe these scenarios. If a LMA acknowledges each physical interface, the LMA allocates mobility sessions for each interface and each mobility session for the each physical interface is generated. But, if a LMA acknowledges only a logical interface, the LMA allocates a mobility session for the logical interface of the mobile node and one mobility session for the logical interface is generated.

For the regarding of second aspect, in basic PMIPv6 specification, if a LMA allocates multiple home network prefixes to a multiple interfaces mobile node, these multiple home network prefixes are totally shown to the host IP stack of the mobile node. This is also effective when a logical interface is used. But, due to the usage of logical interface in a multiple interfaces mobile node in PMIPv6 domain, we can extend the allocation method of multiple home network prefixes to a mobile node. As same as the role of a logical interface to hide the change of multiple interfaces, the logical interface can hide the existence and the change of multiple home network prefixes. In section 4.3, section 4.4, we describe more detail.

For the regarding of third aspect, if a LMA acknowledges only a logical interface, this description is no longer effective because only one logical interface is shown to the LMA and the LMA assumes that the mobile node has one interface even though it has multiple physical interfaces. But, the PMPv6 specification SHOULD be extended to consider a handoff between two different physical interfaces of a mobile node with a logical interface.

4.  The usage of multiple home network prefixes on a logical interface

4.1.  Scenario 1 – LMA acknowledges each physical interface of a MN

The first scenario of the usage of multiple home network prefixes on a logical interface is same as described in internet draft of "Proxy Mobile IPv6 Extensions to Support Flow Mobility [I‑D.bernardos‑netext‑pmipv6‑flowmob‑00] (Bernardos, CJ., Jeyatharan, M., Koodli, R., Melia, T., and F. Xia, “Proxy Mobile IPv6 Extensions to Support Flow Mobility, draft-melia-bernardos-netext-pmipv6-flowmob-00 (work in progress),” July 2010.).” The role of a logical interface is only to hide the existence of multiple network interfaces and the change of network interfaces for inter-technology handoff and flow mobility in a mobile node point of view. So, the logical interface is transparent to the LMA. In this scenario, link-layer identifiers of each physical interface are delivered to a LMA through proxy binding update. So, the LMA acknowledges each physical interfaces and it generates each mobility session for each physical interface.

Figure 1 shows this case. As shown in Figure 1, if the mobile node uses two physical interfaces if_1 and if_2, these two different physical interfaces are referred as different LL-ID (link-layer identifier) xxx, yyy. As a result of proxy binding update, two different mobility sessions of two physical interfaces are generated.

                                    LMA's Binding Table
                                    +================================+
                           +----+   | HNP   MN-ID  CoA   ATT   LL-ID |
                           |LMA |   +================================+
                           +----+   | HNP-1  MN-1  PCoA-1  5    xxx  |
                            //\\    | HNP-2  MN-1  PCoA-2  4    yyy  |
                 +---------//--\\-----------+
                (         //    \\           )
                (        //      \\          )
                 +------//--------\\--------+
                       //          \\
               PCoA-1 //            \\ PCoA-2
                   +----+          +----+
            (WLAN) |MAG1|          |MAG2| (WiMAX)
                   +----+          +----+
                      \               /
                       \             /
                  HNP-1 \           / HNP-2
                         \         /
                          \       /
                     +-------+ +-------+
                     | if_1  | | if_2  |
        (LL-ID: xxx) |(WLAN) | |(WiMAX)| (LL-ID: yyy)
                     +-------+-+-------+
                     |     Logical     |
        (LL-ID: ZZZ) |    Interface    | HNP-1::zzz/128
                     +-----------------| HNP-2::zzz/128
                     |       MN        |
                     +-----------------+

4.2.  Scenario 2 – LMA acknowledges logical interface of a MN

The role of a logical interface is to hide the existence of multiple network interfaces and the change of network interfaces for inter-technology handoff and flow mobility in a mobile node point of view. Also, in a LMA point of view, the LMA acknowledges only a logical interface and it generates mobility sessions for the logical interface. In this scenario, only link-layer identifier of a logical interface is delivered to a LMA during proxy binding update even though multiple physical interfaces are used.

Figure 2 shows this case. As shown in Figure 2, the mobile node uses two physical interfaces if_1 and if_2 and these two different physical interfaces are referred as different LL-ID xxx, yyy. But, instead of using LL-IDs of each physical interface, the LL-ID of the logical interface zzz is used in a LMA's binding table. As a result of proxy binding update, mobility session of the logical interface is generated.

                                    LMA's Binding Table
                                    +================================+
                           +----+   | HNP   MN-ID  CoA   ATT   LL-ID |
                           |LMA |   +================================+
                           +----+   | HNP-1  MN-1  PCoA-1  5    zzz  |
                            //\\    | HNP-2  MN-1  PCoA-2  4    zzz  |
                 +---------//--\\-----------+
                (         //    \\           )
                (        //      \\          )
                 +------//--------\\--------+
                       //          \\
               PCoA-1 //            \\ PCoA-2
                   +----+          +----+
            (WLAN) |MAG1|          |MAG2| (WiMAX)
                   +----+          +----+
                      \               /
                       \             /
                  HNP-1 \           / HNP-2
                         \         /
                          \       /
                     +-------+ +-------+
                     | if_1  | | if_2  |
        (LL-ID: xxx) |(WLAN) | |(WiMAX)| (LL-ID: yyy)
                     +-------+-+-------+
                     |     Logical     |
        (LL-ID: ZZZ) |    Interface    | HNP-1::zzz/128
                     +-----------------| HNP-2::zzz/128
                     |       MN        |
                     +-----------------+

4.3.  Scenario 3 – All home network prefixes are shown to IP host stack

The third scenario of the usage of multiple home network prefixes on a logical interface is same as described in internet draft of "Logical Interface Support for multi-mode IP Hosts [I‑D.ietf‑netext‑logical‑interface‑support‑00] (Melia, T. and S. Gundavelli, “Logical Interface Support for multi-mode IP Hosts, draft-ietf-netext-logical-interface-support-00 (work in progress),” September 2010.)” and “Proxy Mobile IPv6 Extensions to Support Flow Mobility [I‑D.bernardos‑netext‑pmipv6‑flowmob‑00] (Bernardos, CJ., Jeyatharan, M., Koodli, R., Melia, T., and F. Xia, “Proxy Mobile IPv6 Extensions to Support Flow Mobility, draft-melia-bernardos-netext-pmipv6-flowmob-00 (work in progress),” July 2010.).” The role of a logical interface is only to hide the existence of multiple network interfaces and the change of network interfaces. The home network prefixes that a LMA allocates to a multiple interface mobile node are totally shown to host IP stack of the mobile node. The logical interface simply bypasses the home network prefixes between host IP stack and each physical interface.

Figure 3 shows this case. As shown in Figure 3, if the LMA allocates two home network prefixes HNP-1, HNP-2 to the mobile node, these two home network prefixes are shown to IP host stack of the mobile node. As a result of receiving multiple home network prefixes in IP host stack, two different IPv6 addresses HNP-1::zzz/128 and HNP-2::zzz/128 can be generated.

                                    LMA's Binding Table
                                    +================================+
                           +----+   | HNP   MN-ID  CoA   ATT   LL-ID |
                           |LMA |   +================================+
                           +----+   | HNP-1  MN-1  PCoA-1  5    ZZZ  |
                            //\\    | HNP-2  MN-1  PCoA-2  4    ZZZ  |
                 +---------//--\\-----------+
                (         //    \\           )
                (        //      \\          )
                 +------//--------\\--------+
                       //          \\
               PCoA-1 //            \\ PCoA-2
                   +----+          +----+
            (WLAN) |MAG1|          |MAG2| (WiMAX)
                   +----+          +----+
                      \               /
                       \             /
                  HNP-1 \           / HNP-2
                         \         /
                          \       /
                     +-------+ +-------+
                     | if_1  | | if_2  |
        (LL-ID: xxx) |(WLAN) | |(WiMAX)| (LL-ID: yyy)
                     +-------+-+-------+
                     |     Logical     |
        (LL-ID: ZZZ) |    Interface    | HNP-1::zzz/128
                     +-----------------| HNP-2::zzz/128
                     |       MN        |
                     +-----------------+

4.4.  Scenario 4 – Only one home network prefix is shown to IP host stack

In above scenario 3, basic PMIPv6 operations can be applied even though a logical interface is used. Multihoming support and inter-technology handoff support is provided without any modification of PMIPv6 operations but for flow mobility, it needs method to transfer a subset of multiple home network prefixes which are assigned to multiple interfaces of the host.

In scenario 3, one application that uses one specific home network prefix cannot utilize the multiplicity of home network prefixes. For on-going session continuity, applications cannot change their home network prefix during packet sending/receiving. Even though a logical interface supports the inter-technology handoff between different network interfaces, applications should use same home network prefix before/after handoff.

But, if a logical interface supports the change of network interface and also the change of home network prefix, applications can utilize the multiplicity of home network prefixes. As a same manner of the handling of network interface, only one home network prefix is shown to host IP stack of the mobile node. And the logical interface manages the relation between multiple home network prefixes and the home network prefix that is shown to host IP stack and dynamically update them. In this case, only one logical interface and one home network prefix is shown to host IP stack of the mobile node.

Figure 4 shows this case. As shown in Figure 4, if the LMA allocates two home network prefixes HNP-1, HNP-2 to the mobile node, only one home network prefix is shown to IP host stack of the mobile node. As a result of receiving single home network prefix in IP host stack, one IPv6 addresses HNP-1::zzz/128 can be generated.

                                    LMA's Binding Table
                                    +================================+
                           +----+   | HNP   MN-ID  CoA   ATT   LL-ID |
                           |LMA |   +================================+
                           +----+   | HNP-1  MN-1  PCoA-1  5    zzz  |
                            //\\    | HNP-2  MN-1  PCoA-2  4    zzz  |
                 +---------//--\\-----------+
                (         //    \\           )
                (        //      \\          )
                 +------//--------\\--------+
                       //          \\
               PCoA-1 //            \\ PCoA-2
                   +----+          +----+
            (WLAN) |MAG1|          |MAG2| (WiMAX)
                   +----+          +----+
                      \               /
                       \             /
                  HNP-1 \           / HNP-2
                         \         /
                          \       /
                     +-------+ +-------+
                     | if_1  | | if_2  |
        (LL-ID: xxx) |(WLAN) | |(WiMAX)| (LL-ID: yyy)
                     +-------+-+-------+
                     |     Logical     |
        (LL-ID: ZZZ) |    Interface    |
                     +-----------------| HNP-1::zzz/128
                     |       MN        |
                     +-----------------+

5.  Security Considerations

TBD.

6.  IANA Considerations

This document has no actions for IANA.

7.  References

7.1. Normative References

7.2. Informative References

Authors' Addresses