DMM K. Xue Internet-Draft L. Li Intended status: Standards Track P. Hong Expires: June 29, 2013 USTC P. McCann Huawei December 26, 2012 Routing optimization in DMM draft-xue-dmm-routing-optimization-01.txt Abstract This draft proposes a PMIP-based routing optimization method in distributed anchor architecture. The anchor of the mobile node is able to communicate with the anchor of corresponding node directly using optimized routing. In this draft, there are two modes for the setup of routing optimization: the direct mode and the relay mode. The difference of them lies in that the routing optimization is set up directly or under the assistance of a third anchor. The situation that Communication Node(CN) is a fixed terminal or a content server is also considered and 3 solutions are provided correspondingly. The method proposed in this draft can reduce the delay and ve signaling overhead in the current scheme. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 29, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. Xue, et al. Expires June 29, 2013 [Page 1] Internet-Draft Routing optimization in DMM December 2012 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Xue, et al. Expires June 29, 2013 [Page 2] Internet-Draft Routing optimization in DMM December 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 2.1. Conventions Used in This Document . . . . . . . . . . . . 4 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Long Routing in Current Distributed Anchor Scenario . . . 5 3.2. Signaling Overhead Analysis . . . . . . . . . . . . . . . 6 4. The Function of D-MAG . . . . . . . . . . . . . . . . . . . . 7 5. Overview of the Proposed Protocol . . . . . . . . . . . . . . 7 5.1. The Direct Mode . . . . . . . . . . . . . . . . . . . . . 8 5.2. The Relay Mode . . . . . . . . . . . . . . . . . . . . . . 10 6. CN considerations . . . . . . . . . . . . . . . . . . . . . . 12 6.1. The Direct Mode . . . . . . . . . . . . . . . . . . . . . 12 6.2. The Relay Mode . . . . . . . . . . . . . . . . . . . . . . 14 6.2.1. P-D-MAG as A Relay . . . . . . . . . . . . . . . . . . 14 6.2.2. F-D-MAG as A Relay . . . . . . . . . . . . . . . . . . 15 7. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 17 7.1. Enhanced Proxy Binding Update Message . . . . . . . . . . 17 7.2. Enhanced Proxy Binding Acknowledgement Message . . . . . . 18 7.3. Mobility option . . . . . . . . . . . . . . . . . . . . . 19 7.3.1. Corresponding node address option . . . . . . . . . . 19 7.3.2. D-MAG address option . . . . . . . . . . . . . . . . . 20 7.3.3. Former tunnels information option . . . . . . . . . . 21 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 11.1. Normative Reference . . . . . . . . . . . . . . . . . . . 23 11.2. Informative Reference . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Xue, et al. Expires June 29, 2013 [Page 3] Internet-Draft Routing optimization in DMM December 2012 1. Introduction The original centralized mobility management methods (such as the Mobile IPv6, 3GPP EPS etc.) have many drawbacks including the long routing problem, non- optimal architecture, heavy signaling overhead etc. Therefore, distributed mobility managements are discussed and studied widely. In the current research of distributed mobility management (DMM), the method that the anchor undertakes the role of both LMA and MAG simultaneously is called the fully distributed mobility management scheme. The distributed anchor [I-D.bernardos-dmm-distributed-anchoring] is one of the fully distributed mobility management methods. The distributed anchor means that the newly generated communication session is anchored by mobile node's current anchor. For example, when the mobile node moves from one anchor to another anchor (handover), the communication sessions generated after the handover are anchored by the new anchor. Under the current distributed anchor schemes, when mobile node moves to a new anchor, the former flow is forwarded by the former anchor to the new anchor. Therefore, the long routing problem still exists. In the existing work of PMIPv6 as [I-D.ietf-netext-pmip-lr], the communication between LMAs is not involved since it assumes the mobility management function should be accomplished under the centralized architecture. However, in the distributed architecture aforementioned, each distributed anchor could be regarded as the LMA for the communication session generated on it. Therefore, it is necessary to have communications between distributed anchors but current schemes in PMIPv6 do not support such scenario. In this draft, we propose a routing optimization scheme in distributed anchor scenario based on PMIPv6 to solve the non-optimization routing problem in the current work. 2. Conventions and Terminology 2.1. Conventions Used in This Document 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]. 2.2. Terminology The following terms are defined and used in this document: Distributed MAG (D-MAG). It is the distributed anchor in our method Xue, et al. Expires June 29, 2013 [Page 4] Internet-Draft Routing optimization in DMM December 2012 and it provides mobility management function. First D-MAG (F-D-MAG). It is the first hop D-MAG where the sessions firstly start. F-D-MAG assigns IPv6 prefixes and provides mobility management function for the registered mobile node. Previous D-MAG (P-D-MAG). It is the D-MAG that mobile node attaches before handover. New D-MAG (N-D-MAG). It is the D-MAG that mobile node attaches currently. Enhanced Proxy Binding Update (ePBU). It is the enhanced PBU designed for optimized routing tunnel setup, state update, etc. It contains Routing Optimization Indicator (ROI) as a 2-bit state flag Enhanced Proxy Binding Acknowledge (ePBA). It is the enhanced PBA designed for optimized routing tunnel setup, state update, etc. It contains Routing Optimization Indicator (ROI) as a 2-bit state flag 3. Motivations 3.1. Long Routing in Current Distributed Anchor Scenario In current DMM approaches, when the mobile node moves to a new anchor, the communication session generated before MUST be forwarded to the new D-MAG by the original anchor. Therefore, there is still a long routing problem in such schemes and it MAY bring in delay and jitter. As Figure.1 shows, in the current approaches, when the mobile node (MN) moves from P-Anchor(the previous anchor) to N-Anchor(the new anchor), the communication session generated before handover (On P-Anchor) will be forwarded to the new anchor (N-Anchor in Figure.1) by the previous anchor (P-Anchor). The problem would become more severe when the mobile node (MN) moves across multiple anchors with the original communication sessions still going. It is because the distance between the original anchor and the new anchor MAY be rather long for a certain communication session. Xue, et al. Expires June 29, 2013 [Page 5] Internet-Draft Routing optimization in DMM December 2012 +----------+ +----------+ | CN | | CN | | | | | +----/-----+ +----/-----+ | | | _,,,.-----..,,| ,-|` |``-. / | Core Network | \ \ | | / '-|, |_,-' Old session | ``''''----'''`| New session | | | | +----|-----+ +----------+ | +-----------+ | | P-Anchor | || N-Anchor| +----------+ +|---|-----+ | | | | +------+ ---Move--> | MN | +------+ Figure 1: Data flow in the current DMM approaches 3.2. Signaling Overhead Analysis In this section, the analysis of the signaling overhead by simply adopting current routing optimization schemes in PMIPv6 is given briefly. The routing optimization or local routing schemes in current PMIPv6 MAY bring in much more signaling overhead when applied in the distributed anchor scenario. The procedure of local routing is showed in Figure.2. The LMA (Local Mobility Anchor) of MN sends routing optimization trigger to the LMA of CN to start the routing optimization. The LMA of MN also needs to send the address of MN's MAG to the LMA of CN. Afterwards, the LMA of CN sends routing optimization initiation command to the MAG of CN. Then the MAG of CN sets up tunnel with the MAG of MN and the routing optimization is established [I-D.loureiro-netext-pmipv6-ro]. Xue, et al. Expires June 29, 2013 [Page 6] Internet-Draft Routing optimization in DMM December 2012 +-------+ +-------+ +-------+ +-------+ |MAG(MN)| |LMA(MN)| |LMA(CN)| |MAG(CN)| +---/---+ +---/---+ +---/---+ +---/---+ | | | | | | | | | |-1.RO Trigger----->| | | | | | | | |-2.RO Init----->| | | | | |<-------------3.RO Setup----------------------| | | | | |--------------4.RO Setup Ack----------------->| | | | | | | |<-5.RO Init Ack-| | | | | | |<-6.RO Trigger Ack-| | | | | | Figure 2: The procedure of local routing in PMIPv6 If it is adopted in the distributed anchor scenario, each anchor could be regarded as a LMA for the communication sessions generated on it. The mobile node MAY have multiple communication sessions generated on different anchors. When the mobile node moves, each anchor of MN needs to send messages to each CN's anchor. Since the mobile node moves across multiple anchors, there would be multiple LMAs of MN and multiple LMAs of CN. Therefore, the signalling overhead is large. Secondly, these signallings are distributed across the Internet, so the delay would be longer for all of these messages. 4. The Function of D-MAG D-MAG(Distributed MAG) is the distributed anchor in this draft. It is in charge of the prefix allocation and the mobility management for a specific communication session generated on it. It runs the functionalities of PMIP's MAG and LMA based on communication sessions. It is a logical entity that could be integrated into the access router. 5. Overview of the Proposed Protocol We propose two solutions to optimize the routing. The first solution is the Direct Mode which means that the routing optimization is set up between the MN's D-MAG and CN's D-MAG by exchanging messages between the two entities directly. The second solution is the Relay Xue, et al. Expires June 29, 2013 [Page 7] Internet-Draft Routing optimization in DMM December 2012 Mode which means that the routing optimization between the MN's D-MAG and CN's D-MAG SHALL be set up under the assistance of a third D-MAG. There are two stages in our protocol. The first stage is the initiation of the routing optimization and the second stage is the maintenance of the routing optimization. The initiation is the setup procedure of the routing optimization when mobile node moves to a new anchor from the first anchor. The maintenance stage is the maintenance of routing optimization when the mobile node moves from the previous anchor to the new anchor after the setup of routing optimization. 5.1. The Direct Mode (a)Initiation of Routing Optimization Figure 3 illustrates the initiation of routing optimization. The original communication session for MN is generated in F-D-MAG and uses the prefix it assigns. The F-D-MAG is the first hop D-MAG where the session firstly starts. When MN moves to its N-D-MAG, MN's N-D-MAG sends enhanced PBU (ePBU) with ROI (Routing Optimization Indicator) = 01 to its F-D-MAG to inform that the prefixes it assigns are still being used. ePBU is an enhanced proxy binding update (ePBU) with a 2-bit state flag ROI. This message is OPTIONAL because there is already a prefix lifetime extension message in the protocol of PMIPv6 as [RFC5213]. MN's N-D-MAG sends ePBU with ROI= 10 to CN's F-D-MAG to query the address of CN's current D-MAG. We MAY assume the address of CN's F-D-MAG is known to MN's N-D-MAG. Even if it is unknown to MN's N-D- MAG, the ePBU to CN's F-D-MAG could be delivered in the following way. Firstly, MN's D-MAG intercepts the first uplink packet of MN and gets the address of CN which is the destination address of the packet. Then, it sends ePBU to the address of CN and the ePBU would be intercepted by CN's F-D-MAG. Afterwards, CN's F-D-MAG would recognize the ePBU and sends back enhanced PBA (ePBA) which includes the address of CN's current D-MAG. MN's N-D-MAG sends ePBU with ROI=11 to CN's current D-MAG to execute the routing optimization. Under this circumstance, a bi-directional tunnel will be established between MN's N-D-MAG and CN's D-MAG. Xue, et al. Expires June 29, 2013 [Page 8] Internet-Draft Routing optimization in DMM December 2012 +------+ +---------+ +---------++---------++---------+ +------+ | MN | | N-D-MAG | | F-D-MAG || F-D-MAG || D-MAG | | CN | | | | (MN) | | (MN) || (CN) || (CN) | | | +--/---+ +----/----+ +----/----++----/----++----/----+ +--/---+ | | | | | | |<-1.Attach-| | | | | | /RS | | | | | | 2.Registration | | | | | | | | | | | |-3.ePBU(ROI)->| | | | | | | | | | | |<-4.ePBA(ROI)-| | | | | | | | | | | |-----5.ePBU(ROI)-------->| | | | | | | | | | |<----6.ePBA(ROI)---------| | | | | | | | | | |-----------7.ePBU(ROI)------------->| | | | | | | | | |<----------8.ePBA(ROI)--------------| | | | | | | | |<-9.RA-----| | | | | | | | | | | |<-10A.IP-->|<---------10B.IP Packet------------>|<-10A.IP->| | packet | | | | packet | Figure 3: The initiation of routing optimization for DM (b)Maintenance of routing optimization Figure 4 illustrates procedure of the maintenance for routing optimization When MN moves from previous D-MAG(P-D-MAG) to another new D-MAG (N-D- MAG in Figure 4), N-D-MAG sends ePBU with ROI = 01 to F-D-MAG in order to announce the prefixes that F-D-MAG assigns are still being used. It is also OPTIONAL and the reason is the same with that in section 5.1(a). N-D-MAG sends ePBU with ROI=00 to P-D-MAG to request former tunnel information on P-D-MAG. The tunnel information contains all the addresses of CNs' current D-MAGs. P-D-MAG sends back ePBA with ROI=00 which includes the former tunnel information. The mobile node MAY move across multiple D-MAGs, therefore, it could have multiple routing optimization tunnels on P-D-MAG. The information of all the tunnels could be obtained through one exchange of message (message 6 and 7 in Figure 4). In this way, the signaling overhead mentioned in Xue, et al. Expires June 29, 2013 [Page 9] Internet-Draft Routing optimization in DMM December 2012 Section 3.2 can be reduced. The former tunnels on P-D-MAG could be deleted explicitly through the exchange of ePBU/ePBA between N-D-MAG and P-D-MAG, or they would be deleted upon timer expiration. Then N-D-MAG of MN sends ePBU with ROI=11 to each CN's D-MAG of CN to maintain routing optimization. Under this circumstance, a bi- directional tunnel would be established between the N-D-MAG(MN) and each D-MAG(CN). Consequently, the routing optimization could be continued. +------+ +---------+ +---------++---------++---------+ +------+ | MN | | N-D-MAG | | F-D-MAG || P-D-MAG || D-MAG | | CN | | | | (MN) | | (MN) || (MN) || (CN) | | | +--/---+ +----/----+ +----/----++----/----++----/----+ +--/---+ |<----------1A.IP packet------------->|<-1B.IP-->|<-1C.IP-->| |<-2.Attach-| | | packet | packet | | /RS | | | | | | 3.Registration | | | | | | | | | | | |-4.ePBU(ROI)->| | | | | | | | | | | |<-5.ePBA(ROI)-| | | | | | | | | | | |-----6.ePBU(ROI)-------->| | | | | | | | | | |<----7.ePBA(ROI)---------| | | | | | | | | | |-----------8.ePBU(ROI)------------->| | | | | | | | | |<----------9.ePBA(ROI)--------------| | | | | | | | |<-10.RA----| | | | | | | | | | | |<-11A.IP-->|<---------11B.IP packet------------>|<-11A.IP->| | packet | | | | packet | Figure 4: The maintenance of routing optimization for direct mode 5.2. The Relay Mode (a)Initiation of routing optimization In relay mode, the initiation of routing optimization is the same with that in the direct mode described in section 5.1(a). (b)Maintenance of routing optimization Xue, et al. Expires June 29, 2013 [Page 10] Internet-Draft Routing optimization in DMM December 2012 Figure 5 illustrates the procedure of maintenance stage for relay mode. +------+ +---------+ +---------++---------++---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG || P-D-MAG || D-MAG | | CN | | | | (MN) | | (MN) || (MN) || (CN) | | | +--/---+ +----/----+ +----/----++----/----++----/----+ +--/--+ |<----------1A.IP packet------------->|<-1B.IP-->|<-1C.IP-->| |<-2.Attach-| | | packet | packet | | /RS | | | | | | 3.Registration | | | | | | | | | | | |-4.ePBU(ROI)->| | | | | | | | | | | |<-5.ePBA(ROI)-| | | | | | | | | | | |-----6.ePBU(ROI)-------->| | | | | | |-7.ePBU-->| | | | | | (ROI) | | | | | |<-8.ePBA--| | | | | | (ROI) | | | |<----9.ePBA(ROI)---------| | | | | | | | | |<-10.RA----| | | | | | | | | | | |<-11A.IP-->|<---------11B.IP Packet------------>|<-11A.IP->| | packet | | | | packet | Figure 5: The maintenance of routing optimization for relay mode When MN moves from previous D-MAG(P-D-MAG) to another new D-MAG(N-D- MAG), namely the N-D-MAG in Figure 5, N-D-MAG sends ePBU with ROI = 01 to F-D-MAG in order to announce the prefixes that F-D-MAG assigns are still being used. It is also OPTIONAL and the reason is the same with that in section 5.1(a). N-D-MAG of MN sends ePBU with ROI=00 to P-D-MAG of MN to request the context transfer of routing optimization. P-D-MAG of MN sends ePBU with ROI=11 to each D-MAG of CN to maintain routing optimization. P-D-MAG of MN works as a relay for the request of routing optimization maintenance. Finally, P-D-MAG of MN sends back the ePBA to MN's N-D-MAG. The ePBA contains the address of CN's D-MAG. Therefore, the data could be transmitted using optimized routing. Xue, et al. Expires June 29, 2013 [Page 11] Internet-Draft Routing optimization in DMM December 2012 When there are multiple tunnels established in the P-D-MAG, only one pair of ePBU/ePBA (message 6 and 9) exchange between the N-D-MAG (MN) and P-D-MAG (MN) is needed to acquire all the tunnel information. In this way, we save the signaling overhead. Besides, the message querying for the tunnel information from N-D-MAG to P-D-MAG does not need to be delivered through the Internet, which would reduce the signaling delay than querying from the F-D-MAG of CN over the Internet. 6. CN considerations CN could also be a fixed terminal or a content server and it is capable to set up tunnels with the MN's D-MAG. For such CN, we also provide two modes, the direct mode and the relay mode. Likewise, there are also two stages. The first one is the initiation stage and the other one is the maintenance stage. This consideration requires CN to support the ability of tunnel setup like exchanging message with D-MAG. 6.1. The Direct Mode (a) Initiation of routing optimization +------+ +---------+ +---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG | | CN | | | | (MN) | | (MN) | | | +--/---+ +----/----+ +----/----+ +--/--+ | | | | |<-1.Attach-| | | | /RS | | | | 2.Registration | | | | | | | |-3.ePBU(ROI)->| | | | | | | |<-4.ePBA(ROI)-| | | | | | | |-----5.ePBU(ROI)------->| | | | | | |<----6.ePBA(ROI)--------| | | | | |<-7.RA-----| | | | | | | |<--8A.IP-->|<---8B.IP packet------->| | packet | | | Figure 6: The initiation stage for direct mode Xue, et al. Expires June 29, 2013 [Page 12] Internet-Draft Routing optimization in DMM December 2012 Figure 6 illustrates the initiation stage for these special CNs in the direct mode. The original session is generated in F-D-MAG and uses the prefixes it assigns. When MN moves, N-D-MAG sends ePBU (set ROI = 01) to F-D-MAG to inform that the prefixes it assigns are still being used. This step is optional and the reason is the same with that in section 5.1(a). N-D-MAG sends ePBU (set ROI = 11) to all CNs to inform of the execution of routing optimization. Under this circumstance, a bi- directional tunnel will be established between N-D-MAG and CN. (b) Maintenance of routing optimization +------+ +---------+ +---------++---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG || P-D-MAG | | CN | | | | (MN) | | (MN) || (MN) | | | +--/---+ +----/----+ +----/----++----/----+ +--/--+ |<----------1A.IP packet------------->|<-1B.IP-->| |<-2.Attach-| | | packet | | /RS | | | | | 3.Registration | | | | | | | | | |-4.ePBU(ROI)->| | | | | | | | | |<-5.ePBA(ROI)-| | | | | | | | | |-----6.ePBU(ROI)-------->| | | | | | | | |<----7.ePBA(ROI)---------| | | | | | | | |----------8.ePBU(ROI)-------------->| | |<---------9.ePBA(ROI)---------------| |<-10.RA----| | | | | | | | | |<-11A.IP-->|<---------11B.IP Packet------------>| | packet | | | | Figure 7: The maintenance stage for direct mode Figure 7 illustrates the maintenance stage for these special CNs in direct mode. The original session is generated in F-D-MAG and uses the prefixes F-D-MAG assigns. Xue, et al. Expires June 29, 2013 [Page 13] Internet-Draft Routing optimization in DMM December 2012 When MN moves from P-D-MAG to N-D-MAG, N-D-MAG sends ePBU (set ROI = 01) to F-D-MAG to inform that the prefixes it assigns are still being used. This step is optional and the reason is the same with that in section 5.1(a). N-D-MAG optionally sends ePBU (set ROI = 00) to P-D-MAG to deletes all the former tunnels related to that MN explicitly. For multiple tunnels related to the MN，only one pair of ePBU/ePBA is required. N-D-MAG sends ePBU (set ROI = 11) to all CNs to inform of the execution of routing optimization. Under this circumstance, a bi- directional tunnel will be established between N-D-MAG and CNs. 6.2. The Relay Mode There are two types of relays, the first type is the P-D-MAG relay and the other one is the F-D-MAG relay. The difference lies in that the routing optimization request is relayed by different D-MAGs. 6.2.1. P-D-MAG as A Relay +------+ +---------+ +---------++---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG || P-D-MAG | | CN | | | | (MN) | | (MN) || (MN) | | | +--/---+ +----/----+ +----/----++----/----+ +--/--+ |<----------1A.IP packet------------->|<-1B.IP-->| |<-2.Attach-| | | packet | | /RS | | | | | 3.Registration | | | | | | | | | |-4.ePBU(ROI)->| | | | | | | | | |<-5.ePBA(ROI)-| | | | | | | | | |-----6.ePBU(ROI)-------->| | | | | |-7.ePBU-->| | | | | (ROI) | | | | | | | | | |<-8.ePBA--| | |<----9.ePBA(ROI)---------| (ROI) | |<-10.RA----| | | | | | | | | |<-11A.IP-->|<---------11B.IP Packet------------>| | packet | | | | Xue, et al. Expires June 29, 2013 [Page 14] Internet-Draft Routing optimization in DMM December 2012 Figure 8: The maintenance stage for P-D-MAG relay. Like the relay mode described in section 5.2, the P-D-MAG works as a relay at the stage of routing optimization maintenance. (a) Initiation of routing optimization The initiation stage is the same with that in direct mode of section 6.1(a). (b) Maintenance of routing optimization Figure 8 illustrates the procedure of maintenance stage for P-D-MAG relay. When MN moves, N-D-MAG sends ePBU with ROI=01 to F-D-MAG to inform that the prefixes it assigns are still being used. This step is optional and the reason is the same with that in section 5.1(a). N-D-MAG sends ePBU to P-D-MAG with ROI=00 to request the transferring of former tunnels. P-D-MAG sends ePBU with ROI = 11 to CNs to inform of the execution of routing optimization. The address of N-D-MAG is included in this ePBU (message 7). In this way, P-D-MAG works as a relay. P-D-MAG deletes the former tunnels and sends ePBA with ROI = 11 back to N-D-MAG. Under this circumstance, a bi-directional tunnel will be established between N-D-MAG and CNs and data is transmitted in optimized routing. 6.2.2. F-D-MAG as A Relay In this section, the F-D-MAG works as the relay for both the initiation and maintenance stage of routing optimization. (a) Initiation of routing optimization Xue, et al. Expires June 29, 2013 [Page 15] Internet-Draft Routing optimization in DMM December 2012 +------+ +---------+ +---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG | | CN | | | | (MN) | | (MN) | | | +--/---+ +----/----+ +----/----+ +--/--+ | | | | |<-1.Attach-| | | | /RS | | | | 2.Registration | | | |-3.ePBU(ROI)->| | | | | | | | |-4.ePBU->| | | | (ROI) | | | | | | | |<-5.ePBA-| | |<-6.ePBA(ROI)-| (ROI) | |<-7.RA-----| | | | | | | |<--8A.IP-->|<---8B.IP packet------->| | packet | | | Figure 9: The initiation stage of F-D-MAG relay Figure 9 illustrates the initiation stage of F-D-MAG relay. The original session is generated in F-D-MAG and uses the prefixes F-D-MAG assigns. When MN moves, N-D-MAG sends ePBU with ROI = 01 to F-D-MAG to inform that the prefixes it assigns are still being used and that the Routing Optimization Communication mode is used. F-D-MAG sends ePBU with set ROI = 11 to CN to inform the execution of routing optimization. In this message (message 4), it tells CN the address of N-D-MAG which is the new care of address of MN. In this way, F-D-MAG works as a relay for the request of routing optimization for N-D-MAG. Afterwards, the data could be transmitted between N-D- MAG and CN using optimized routing. (b) Maintenance of routing optimization Figure 10 illustrates the maintenance stage when F-D-MAG works as a relay. When MN moves from P-D-MAG to N-D-MAG, N-D-MAG sends ePBU with ROI =01 to F-D-MAG to inform that the prefixes it assigns are still being used and inform to keep using the Routing Optimization Communication mode. Xue, et al. Expires June 29, 2013 [Page 16] Internet-Draft Routing optimization in DMM December 2012 +------+ +---------+ +---------++---------+ +-----+ | MN | | N-D-MAG | | F-D-MAG || P-D-MAG | | CN | | | | (MN) | | (MN) || (MN) | | | +--/---+ +----/----+ +----/----++----/----+ +--/--+ |<----------1A.IP packet------------->|<-1B.IP-->| |<-2.Attach-| | | packet | | /RS | | | | | 3.Registration | | | | |-4.ePBU(ROI)->| | | | | |----5.ePBU(ROI)----->| | | |<---6.ePBA(ROI)------| | |<-7.ePBA(ROI)-| | | | | | | | |<-10.RA----| | | | | |-----9.ePBU(ROI)-------->| | | |<---10.ePBA(ROI)---------| | | | | | | | | | | | |<-11A.IP-->|<---------11B.IP Packet------------>| | packet | | | | Figure 10: The maintenance stage for F-D-MAG relay F-D-MAG sends ePBU with set ROI = 11 to CN to inform the execution of routing optimization. In this message (message 5), it tells CN the address of N-D-MAG which is the new care of address of MN. In this way, F-D-MAG works as a relay for the request of routing optimization for N-D-MAG. N-D-MAG optionally informs P-D-MAG to delete the former tunnel explicitly or wait upon timer expiration. For multiple sessions related to the MN，only one pair of ePBU/ePBA is required. So it MAY save the signaling overhead. 7. Message Format 7.1. Enhanced Proxy Binding Update Message Xue, et al. Expires June 29, 2013 [Page 17] Internet-Draft Routing optimization in DMM December 2012 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|L|K|M|R|P|ROI| Reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The enhanced PBU (ePBU) is the original proxy binding update added with 2-bit ROI state flag. ROI: 2-bit state flag. Mobility options: A variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero or more TLV-encoded mobility options. The encoding and format of defined options are described in Section 6.2 of [RFC6275]. The distributed mobile access gateway MUST ignore and skip any options that it does not understand. As per this specification, the following mobility options are valid in an Enhanced Proxy Binding Update message. These options can be present in the message in any order. There cannot be more than one instance of any of the following options: Corresponding node's address option D-MAG address option Former tunnels information option 7.2. Enhanced Proxy Binding Acknowledgement Message The enhanced PBA (ePBA) is the original proxy binding acknowledgement added with 2-bit ROI state flag. Xue, et al. Expires June 29, 2013 [Page 18] Internet-Draft Routing optimization in DMM December 2012 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status |K|R|P|ROI| Rev | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ROI: 2-bit state flag. Mobility options: A variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero or more TLV-encoded mobility options. The encoding and format of defined options are described in Section 6.2 of [RFC6275]. The distributed mobile access gateway MUST ignore and skip any options that it does not understand. As per this specification, the following mobility options are valid in an Enhanced Proxy Binding Acknowledgement message. These options can be present in the message in any order. There cannot be more than one instance of any of the following options: Corresponding node address option D-MAG address option Former tunnels information option 7.3. Mobility option 7.3.1. Corresponding node address option A new option, corresponding node address option is defined for use with the Enhanced Proxy Binding Update and Enhanced Proxy Binding Acknowledgement messages exchanged between the distributed mobile access gateways. This option is used for exchanging the corresponding node's address. Xue, et al. Expires June 29, 2013 [Page 19] Internet-Draft Routing optimization in DMM December 2012 The format of the corresponding node address option is shown below. Based on the size of the identifier, the option MUST be aligned appropriately, as per mobility option alignment requirements specified in [RFC6275]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Corresponding Node's Address + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: Approval of new corresponding node address option type value is to be made through IANA Expert Review. Length: 8-bit unsigned integer, representing the length in octets of the mobility option, not including the Option Type and Option Length fields. Corresponding Node's Address: A variable length field containing the corresponding node's address. 7.3.2. D-MAG address option A new option, D-MAG address option is defined for use with the Enhanced Proxy Binding Acknowledgement messages exchanged between the distributed mobile access gateways. This option is used for exchanging current D-MAG address of the corresponding node. The format of the D-MAG address option is shown below. Based on the size of the identifier, the option MUST be aligned appropriately, as per mobility option alignment requirements specified in [RFC6275]. Xue, et al. Expires June 29, 2013 [Page 20] Internet-Draft Routing optimization in DMM December 2012 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + D-MAG's Address + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: Approval of new D-MAG address option value is to be made through IANA Expert Review. Length: 8-bit unsigned integer, representing the length in octets of the mobility option, not including the Option Type and Option Length fields. D-MAG's Address: A variable length field containing the D-MAG's address. 7.3.3. Former tunnels information option A new option, former tunnels information option is defined for use with the Enhanced Proxy Binding Update and Enhanced Proxy Binding Acknowledgement messages exchanged between the distributed mobile access gateways. This option is used for exchanging the information of former tunnels. The format of the former tunnels information option is shown below. Based on the size of the identifier, the option MUST be aligned appropriately, as per mobility option alignment requirements specified in [RFC6275]. Type: Approval of former tunnels information option type value is to be made through IANA Expert Review. Length: 8-bit unsigned integer, representing the length in octets of the mobility option, not including the Option Type and Option Length Xue, et al. Expires June 29, 2013 [Page 21] Internet-Draft Routing optimization in DMM December 2012 fields. This field can also indicate the number of former tunnels listed in the option. The Destination Address of The Xth Tunnel: It indicates the address of the Xth tunnel. The SPI value of The Xth Tunnel: It indicates the SPI value of the Xth tunnel. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | The Destination Address of The 1st Tunnel | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | The SPI value of The 1st Tunnel | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | The Destination Address of The 2nd Tunnel | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | The SPI value of The 2nd Tunnel | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ....... | . ....... . . ....... . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 8. Security Considerations Security threats for routing optimization in network-based distributed mobility management comprise the danger of unauthorized set up or redirect of an established forwarding path by a malicious node. Signaling messages of this protocol between D-MAGs must be authenticated by means of IPsec [RFC4301]. Protection of signaling messages between D-MAGs uses the mechanisms of Encapsulating Security Payload (ESP) [RFC4301] in transport mode with mandatory data origin authentication by means of a non-null payload authentication algorithm. The use of encryption is optional. In particular, if the network which interconnects two D-MAGs is not trusted, the use of encryption is recommended to support confidentiality protection between MAGs respectively. Xue, et al. Expires June 29, 2013 [Page 22] Internet-Draft Routing optimization in DMM December 2012 9. IANA Considerations This document defines three new Mobility Header options, the Corresponding Node Address option, the D-MAG Address option, the Former Tunnels Information option. These options are described in Section 7.3 The new Mobility Header Type values for the ePBU/ePBA should be allocated and the approval of new type values is to be made through IANA Expert Review. The Corresponding Node Address option, defined in Section 7.3.1, is used to exchange Corresponding Node Address between distributed mobile access gateways. The approval of new type value is to be made through IANA Expert Review. The D-MAG Address option, defined in Section 7.3.2, is used to exchange the current D-MAG address of the corresponding node between distributed mobile access gateways. The approval of new type value is to be made through IANA Expert Review. The Former Tunnels Information option, defined in Section 7.3.3, is used to exchange Former Tunnels Information between distributed mobile access gateways. The approval of new type value is to be made through IANA Expert Review. This document also creates a 2-bit status flags in the Proxy Binding Update/Proxy Binding Acknowledgement message called the "Routing Optimization Indicator" in Section 7. 10. Acknowledgements The authors would like to specially thank Peter J. McCann for his thorough reviews of this document.The authors would also like to thank Lei Zhu, Ning He and Dan Ni for all the discussions on this topic. 11. References 11.1. Normative Reference [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support Xue, et al. Expires June 29, 2013 [Page 23] Internet-Draft Routing optimization in DMM December 2012 in IPv6", RFC 6275, July 2011. 11.2. Informative Reference [I-D.bernardos-dmm-distributed-anchoring] Bernardos, C. and J. Zuniga, "PMIPv6-based distributed anchoring", draft-bernardos-dmm-distributed-anchoring-01 (work in progress), September 2012. [I-D.chan-dmm-architecture] Chan, A., "A architecture of distributed mobility management using mip and pmip", draft-chan-dmm-architecture-00 (work in progress), March 2012. [I-D.ietf-netext-pmip-lr] Krishnan, S., Koodli, R., Loureiro, P., Wu, W., and A. Dutta, "Localized Routing for Proxy Mobile IPv6", draft-ietf-netext-pmip-lr-10 (work in progress), May 2012. [I-D.loureiro-netext-pmipv6-ro] Loureiro, P. and M. Liebsch, "Proxy Mobile IPv6 Localized Routing", draft-loureiro-netext-pmipv6-ro-02 (work in progress), March 2010. Authors' Addresses Kaiping Xue USTC Room 305, EEIS Department, USTC West Campus Shushan District, Hefei, Anhui 230027 P. R. China Phone: +86-551-3601334 Email: kpxue@ustc.edu.cn Lin Li USTC Room 305, EEIS Department, USTC West Campus Shushan District, Hefei, Anhui 230027 P. R. China Phone: +86-551-3601334 Email: linl@mail.ustc.edu.cn Xue, et al. Expires June 29, 2013 [Page 24] Internet-Draft Routing optimization in DMM December 2012 Peilin Hong USTC Room 305, EEIS Department, USTC West Campus Shushan Distric, Hefei, Anhui 230027 P. R. China Phone: +86-551-3601334 Email: plhong@ustc.edu.cn Peter J. McCann Huawei 400 Crossing Blvd, 2nd Floor Bridgewater, NJ 08807 USA Phone: +1-908-541-3563 Email: peter.mccann@huawei.com Xue, et al. Expires June 29, 2013 [Page 25]