Network Mobility P. Thubert Internet-Draft Cisco Expires: April 5, 2005 R. Wakikawa Keio University V. Devarapalli Nokia October 5, 2004 NEMO Home Network models draft-ietf-nemo-home-network-models-01 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 5, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This paper documents some usage patterns and the associated issues when deploying a Home Network for NEMO-enabled Mobile Routers, conforming the NEMO Basic Support draft [8]. The aim here is specifically to provide some examples of organization of the Home Network, as they were discussed in NEMO related mailing lists. Thubert, et al. Expires April 5, 2005 [Page 1] Internet-Draft Home Network models with NEMO basic October 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and concepts . . . . . . . . . . . . . . . . . . . 4 3. General Expectations . . . . . . . . . . . . . . . . . . . . . 5 4. Extended Home Network . . . . . . . . . . . . . . . . . . . . 6 4.1 Configuration . . . . . . . . . . . . . . . . . . . . . . 6 4.2 Returning Home . . . . . . . . . . . . . . . . . . . . . . 7 4.3 Applicability . . . . . . . . . . . . . . . . . . . . . . 7 5. Aggregated Home . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 Configuration . . . . . . . . . . . . . . . . . . . . . . 8 5.2 Returning Home . . . . . . . . . . . . . . . . . . . . . . 9 5.2.1 Returning Home by egress . . . . . . . . . . . . . . . 9 5.2.2 Returning Home by ingress . . . . . . . . . . . . . . 10 5.3 Applicability . . . . . . . . . . . . . . . . . . . . . . 10 6. Virtual Home Network . . . . . . . . . . . . . . . . . . . . . 11 6.1 Configuration . . . . . . . . . . . . . . . . . . . . . . 11 6.2 Applicability . . . . . . . . . . . . . . . . . . . . . . 12 7. Mobile Home . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1 Configuration . . . . . . . . . . . . . . . . . . . . . . 13 7.2 Applicability . . . . . . . . . . . . . . . . . . . . . . 14 8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8.1 Changes from version 00 to 01 . . . . . . . . . . . . . . 16 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 18 A. Returning Home emulation in the virtual case . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . 20 Thubert, et al. Expires April 5, 2005 [Page 2] Internet-Draft Home Network models with NEMO basic October 2004 1. Introduction This document assumes that the reader is familiar with IPv6 Mobility as defined in [7], with the NEMO Basic Support [8] and with the NEMO terminology document [10]. In order to read this document properly, the distinction between the concepts of Home Link and of Home Network must be very clear. A Home Link is a physical or a virtual Link, attached to a Home Agent. A Home Network is an aggregation that can be further subnetted. As a result, the Home Network is not necessarily contained on a Home Link. In fact, the Mobile Network Prefixes are subnets of the Home Network. How the two concepts relate in a given deployment depend on the organization of the Home Network, as described below. Four different organizations of the Home Network including a hierarchical construction are documented: Extended Home Network: In this disposition, the Home Network is only one subnet of a larger aggregation that encompasses the Mobile Networks, called extended Home Network. When at Home, a Mobile Router performs normal routing between the Home Link and the Mobile Networks. More in Section 4. Aggregated Home Network: In this disposition, the Home Network actually overlaps with the Mobile Networks. When at Home, a Mobile Router acts as a bridge between the Home Link and the Mobile Networks. More in Section 5. Virtual Home Network: In this disposition, there is no physical Home Link at all for the Mobile Routers to come back Home to. More in Section 6. Mobile Home Network: In this disposition, there is a bitwise hierarchy of Home Networks. A global Home Network is advertised to the infrastructure by a head Home Agent and further subnetted into Mobile Networks. Each subnet is owned by a Mobile Router that registers it in a NEMO fashion while acting as a Home Agent for that network. More in Section 7. In all cases, the Home Agents collectively advertise only the aggregation of the Mobile Networks. The dichotomy is kept within the Home Agents and the Mobile Routers, as opposed to advertised by means of routing protocols to other parties. The examples provided here aim at illustrating the NEMO Basic Support draft [8] but do not aim at limiting its scope of application, and additional cases may be added in the future. Thubert, et al. Expires April 5, 2005 [Page 3] Internet-Draft Home Network models with NEMO basic October 2004 2. Terminology and concepts 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 [1]. The following terms used in this document are defined in the IPv6 Addressing Architecture document [5]: link-local unicast address link-local scope multicast address Most of the mobility related terms used in this document are defined in the Mobility Related Terminology document [6] and in the Mobile IPv6 (MIP6) specification [7]. Additionally, some terms were created or extended for NEMO. These specific terms are defined in the Mobile Network Terminology document [10]: Home Link Home Network Home Address MRHA Tunnel Mobile Aggregated Prefix Aggregated Home Network Extended Home Network Virtual Home Network Mobile Home Network Thubert, et al. Expires April 5, 2005 [Page 4] Internet-Draft Home Network models with NEMO basic October 2004 3. General Expectations With Mobile IPv6, the Home Network is generally a physical network interconnecting the Home Agents, and the Mobile Nodes that are at Home. NEMO extends the concept of Home so that it is not only a flat subnet composed of Home Addresses but an aggregation that is itself subnetted in mobile and Home Networks. This aggregation is still referred to as Home. As an example, say that the aggregation has a global routing prefix of m = 48 bits (A:B:C::/48), with subnet ID size of n = 16 bits ( n + m = 64). Say that a Mobile Router, MR1, owns the MNP A:B:C:1::/64: With NEMO Basic Support, and depending on the deployment, MR1 may register using a Home Address from the Home network, A:B:C:0::1, say, or a Home Address, A:B:C:1::1, say, from one of its MNPs. In a given deployment, one subnet may be reserved for the Home Link (say A:B:C:0::/64) while the others are attributed to Mobile Routers as Mobile Networks (as A:B:C:1::/64 for MR1). Another approach could be to configure the Aggregation of Mobile Networks as the subnet on the Home Link, and let the Mobile Routers manage the overlapping networks. Finally, the aggregation could be configured on a virtual network, with no physical Home Link at all, in which case Home means topologically and administratively close to the Home Agent that owns the virtual network. The following sections provide additional information on these forms of Home Network. Thubert, et al. Expires April 5, 2005 [Page 5] Internet-Draft Home Network models with NEMO basic October 2004 4. Extended Home Network 4.1 Configuration One simple approach is to reserve one or several subnets from an aggregation for the Home Link, and to use the other subnets as MNPs. In that case, the Home Network and the Mobile Networks do not overlap. The aggregation is called an Extended Home Network and depicted in Figure 1. | route v /48 A:B:C::/48 HA | /64 A:B:C:0::/64 --+-----+--+- . -+- . -+-- | | | | MR1 MR2 MRi MRN /64 /64 /64 /64 A:B:C:i::/64 0 < i <= N Extended Home Network <-----------------------------------------------------------> Home Net Mobile Net Mobile Net ... Mobile Net <------------><------------><------------> ... <------------> Figure 1: Extended Home Network In that configuration: o There is one physical Home Network and multiple Mobile Networks o The Home and the MNPs are tailored to allow for IPv6 Stateless Address Autoconfiguration with typical interface identifier length for the type of interface (can be for example /64). o The prefix length of the Extended Home Network is shorter than that of the Home Network and the MNPs, since it is an aggregation (can be for example /48). o The Mobile Routers are assigned individually a Home Address from the Home Network and use is to register their MNP(es). In that case, the Home Agent performs DAD in the Home Network as prescribed by Mobile IPv6 for the Home Addresses. Thubert, et al. Expires April 5, 2005 [Page 6] Internet-Draft Home Network models with NEMO basic October 2004 o Alternatively, a Mobile Router could also form a Home Address from one of its prefixes and use it to register, performing its own DAD on its ingress network. 4.2 Returning Home In the Extended Home Network model, the Home Network is configured on a physical interface of the Home Agent, the Home Link. A Mobile Router returns Home by connecting directly to the Home Link, and dropping the MRHA tunnel. If the Home Address of the Mobile Router is derived from one of its Mobile Network Prefixes, then the MR may connect to the Home Link using an egress interface and autoconfigure an address on the Home Link. The MR recognizes the prefix of its Home Agent in order to decide that it is Home. Note that in that case the Home Address does not match the Home Prefix. When at home, the Mobile Router ensures the connectivity of the Mobile Network using standard router operations. In particular, if the HA has the necessary information to continue routing to the MNPs in the absence of registration, for instance if the Home Address of the Mobile Router is derived from the Home Network, and if the HA uses a static route to the MNP(es) via that address, then the participation of the MR to the Home IGP is not required. But in the general case, when the MR is at Home, it resumes IGP operations on the Home Link in order to advertise its Mobile Networks. Alternate procedures for ensuring the connectivity of the Mobile Networks when at home are described in Section 6. 4.3 Applicability The extended Home Network keeps the MIP6 concept of a Home Network for both Mobile Nodes and Mobile Routers to take their Home Address from. Since there is no overlap between the prefixes that are affected to MNPs and prefix(es) that are dedicated to the Home Link, it is possible for MNs and MRs to coexist with that model. Thubert, et al. Expires April 5, 2005 [Page 7] Internet-Draft Home Network models with NEMO basic October 2004 5. Aggregated Home 5.1 Configuration One other approach is to consider that the Aggregation of all the MNPs is used plainly as the Home Network, referred to as the Aggregated Home Network. This means that the Mobile Aggregated Prefix is configured on the Home Link and advertised by the Home Agent as a subnet, as depicted in Figure 2. HA | /56 Aggreg /56 --+-----+--+- . -+- . -+-- | | | | MR1 MR2 MRi MRN ------ ------ ------ ------ /64 /64 /64 /64 Aggreg|i /64 0 < i <= N Aggregated Home == Home Net <-----------------------------------------------------------> Mobile Net Mobile Net Mobile Net ... Mobile Net <------------><------------><------------> ... <------------> Figure 2: Aggregated Home A node on the Home Link computes that the Aggregated Home Network is actually a subnet on the Home Link and may use it for autoconfiguration purposes. Such a node may also install a connected route to the Aggregated Home Network over the Home Link. As a result, unless the node has a better (longest match) route to a given MNP, it will lookup all MNNs using Neighbor Discovery over the Home Link. Thus, the Home Agent MUST intercept all the packets to the MNNs on the registered prefixes. In order to do so, the Home Agent might perform ND proxying for all addresses in all registered Mobile Network Prefixes, and protect the MNP space from autoconfiguration by uncontrolled visitors on the Home Link. Alternatives based on a routing protocol or ICMP redirect may apply in some cases. Thubert, et al. Expires April 5, 2005 [Page 8] Internet-Draft Home Network models with NEMO basic October 2004 5.2 Returning Home The Aggregated Home Prefix is configured on a physical interface of the Home Agent, the Home Link. As a consequence, the Home Agent has a connected route to the Aggregated Home Network over the Home Link. A Mobile Router returns Home by connecting directly to the Home Link, and dropping the MRHA tunnel. The Mobile Router recognizes its Home Link by a prefix match with its Home Agent. Note that it must expect a shorter prefix than that of its Mobile Networks, even if its Home Address is formed out of one of its MNPs, but that the Home Address matches the Home Network Prefix. Also, Note that in that case, it makes sense for a Mobile Router to register using a Home Address from one of its own MNPs. Taking the Home Address from its own range guarantees the unicity of the suffix. That unicity can be checked by the MR on its ingress network using DAD. 5.2.1 Returning Home by egress A Mobile Router coming Home via its egress interface sees overlapping prefixes between the ingress and the egress interface and some specific support may be needed: When a Mobile Router connects to the Home Link using its egress interface, it might set up a bridge between its ingress interface(s) and the Home Link. Alternatively, the Mobile Router might perform ND proxying for all addresses in its MNPs, between the egress and the related ingress interface. Since the prefixes on the egress and ingress interfaces are overlapping, routing is disallowed. HA | /56 Aggreg /56 --+-----+--+- . -+- . -+-- | | | | MR1 MR2 MRi MRN ------ ------ ------ ------ /64 /64 /64 /64 Aggreg|i /64 0 < i <= N Figure 3: Bridging between egress and ingress Thubert, et al. Expires April 5, 2005 [Page 9] Internet-Draft Home Network models with NEMO basic October 2004 5.2.2 Returning Home by ingress Alternatively, if the MR has a single ingress Interface, the Mobile Router may use the NEMO-Link to connect to the Home Link, merging the two links in a single consistent network. HA | /56 Aggreg /56 --+-----+--+- . -+- . -+-- /64 /64 /64 /64 Aggreg|i /64 0 < i <= N ------ ------ ------ ------ MR1 MR2 MRi MRN | | | | Figure 4: Merging the Home and the Mobile Networks This fits the connected route model, since the Aggregated Home is truly located on that network. Note that in that case, it makes sense for a Mobile Router to register using a Home Address from one of its own MNPs. . 5.3 Applicability With this model, there is no specific space for independent nodes as any address in the aggregation belongs to a MNP, and thus to a Mobile Router. This configuration excludes the cohabitation with MIP6 MNs on the Home Link. A MR that is at Home must own an address from the aggregation on its egress interface and an address from its MNP -a subnet of that aggregation- on its ingress interface. A pure router will reject that configuration, and the MR needs to act as a bridge to enable it. In order to deploy the aggregated Home Network model, one must check whether that support is available in the MRs if returning Home is required. Thubert, et al. Expires April 5, 2005 [Page 10] Internet-Draft Home Network models with NEMO basic October 2004 6. Virtual Home Network 6.1 Configuration The Home Link can be configured on the Home Agent on a virtual link, in which case there's no physical Home Link for Mobile Routers to return Home or for Home Agents to discover each others and perform the ND level interactions as described in Mobile IPv6. [7] /48 eg: A:B:C::/48 HA | /64 A:C:C:E::/64 --+-----+--+- . -+- . -+-- | | | | MR1 MR2 MRi MRN /64 /64 /64 /64 A:B:C:i::/64 0 < i <= N Figure 5: Virtual Home Network The Extended Home Network and the Aggregated Home Network models can be adapted for virtual links. As in the case of a physical link, the Home Address of a Mobile router can be constructed based on a dedicated subnet of the Home Prefix or one of the MR MNPs. Note that since the Home Address is never checked for DAD, it makes the configuration easier to take it from the MNP as opposed to a specific subnet. There are certain advantages to making the Home Link a virtual link: A virtual link may not experience any disruption related to physical maintenance or to hardware problems, so it is more available than a physical link. The high availability of the Home Link is critical for the mobility service. The Home Agent does not have to defend the Mobile Router's Home Address through Proxy Neighbor Discovery. The Home Agent does not also have to perform Duplicate Address Detection (DAD) for the Mobile Router's Home Address when it receives a Binding Update from the Mobile Router. The Mobile Router does not have to implement the Returning Home procedure (section 11.5.4 of Mobile IPv6. [7]). Thubert, et al. Expires April 5, 2005 [Page 11] Internet-Draft Home Network models with NEMO basic October 2004 In order for a Mobile Router to emulate returning Home, it can connect to one or more access link(s) configured for that purpose on the Home Agent. The Mobile Router, after connecting to the access link, SHOULD not send any routing protocol updates on the egress interface because the routing information from the Mobile Router might adversely affect IPv6 route aggregation on the Home Network. However, the Mobile Router must register its binding as if it was accessing a foreign link. There are also some drawbacks to the virtual Home Link approach: There can be only one Home Agent since Mobile IPv6 relies on Neighbor Discovery on the Home Link for other HA discovery and for Duplicate Address Detection. The Home Agent must maintain a Binding Cache entry for a Mobile Router and forwarding state for its Mobile Network even when the Mobile Router is directly connected to it. All traffic to and from the Mobile Network is sent through the bi-directional tunnel regardless of the Mobile Router location. This results in a tunneling overhead even though the Mobile Router is connected to the Home Network. Some solutions can be proposed in order to perform an equivalent of returning Home on a virtual Home Network. One such approach is sketched in appendix as an illustration. 6.2 Applicability At some point in the future, NEMO basic support may be extended to operate fully at L3 for instance if the HAHA protocol [11] gets standardized and deployed. Until then, NEMO operations still inherit from mobile IPv6 [7] for the HA to HA communication, which is basically based on Neighbor Discovery extensions over the Home Link. Making that link virtual bars the deployment of multiple Home Agents, which may be desirable for reasons of load balancing. Please refer to the NEMO multihoming issues [12] draft for more on this. Yet, for a deployment where a single HA is enough, making the Home Link virtual reduces the vulnerability to some attacks and to some hardware failures, while making the HA operation faster. One should check with the product specifications of an HA to see whether the implementation actually supports a Virtual Home Network, and if so, whether in that cases, it is optimized for faster DAD-less bindings. Thubert, et al. Expires April 5, 2005 [Page 12] Internet-Draft Home Network models with NEMO basic October 2004 7. Mobile Home 7.1 Configuration In this disposition, there is a bitwise hierarchy of Home Networks. A global Home Network is advertised to the infrastructure by a head Home Agent(s) and further subnetted into Mobile Networks. As a result, only the Home Agent(s) responsible for the most global (shortest prefix) aggregation receive all the packets for all the MNPs, which are leaves in the hierarchy tree. Each subnet is owned by a Mobile Router that registers it in a NEMO fashion while acting as a Home Agent for that network. This Mobile Router is at Home at the upper level of hierarchy. This configuration is referred to as Mobile Home. An example of that is the Cab Co configuration. Say a Taxi Company owns a /32 prefix. This prefix is advertised at a fixed point, the Headquarters say. Regional offices are deployed around the world. Even though these regional offices are relatively stable in terms of location and prefix requirement -say this changes every few years- making them mobile allows a simpler management when a move has to take place, or should the ISP service change. global Home Network CAB:C0::/32 owned by HQ <-------------------------------------------------------------------> HQ extended Home Net Mobile Home for SFO office (casa) CAB:C0:CA5A::/48 CAB:C0:5F0::/48 <----------------------------> ... <--------------------------------> | Home for offices HQ | CAB:C0:CA5A:CA5A::/64 MN | <----------------------><----> | CAB:C0:CA5A:CA5A::CA5A | CAB:C0:CA5A:CA5A::CA5B | are HAs on link with for each office a route like | | CAB:C0:CA5A:CA5A::5F0 <---------------------- via is the Home addr of SFO office Figure 6: CAB Company HQ configuration Finally, each regional office owns a number of taxis, each one equipped with a mobile router and an associated /64 prefix. Thubert, et al. Expires April 5, 2005 [Page 13] Internet-Draft Home Network models with NEMO basic October 2004 For each Office, say San Francisco (SFO) as an example: Mobile Home Network CAB:C0:5F0::/48 owned by SFO office <------------------------------------------------------------------> SFO Home Network Mobile Networks for taxis for taxis <---------------------...---------------------> CAB:C0:5F0:5F0::/64 CAB:C0:5F0:CAB1::/64 CAB:C0:5F0:....::/6 <-------------------><-------------------> ... <-------------------> CAB:C0:5F0:5F0::5F0 | is HA on link with for | each taxi a route like | | CAB:C0:5F0:5F0::CAB1 <------ via is the Home addrSsync of CAB 1 Figure 7: CAB Company regional configuration Note that the hierarchy occurs at a configuration level and may not be reflected in the actual connection between nodes. For instance in the Cab Co case, cabs are roaming within the city, each one attaching to a different hot spot, while the regional office is connected to the infrastructure using some ISP connection. But it is also possible to reflect the organizational hierarchy in a moving cloud of Mobile Router. If a Mobile Home Agent acts as root-MR for a nested configuration of its own MRs, then the communication between MRs is confined within the nested structure. This can be illustrated in the case of a fleet at sea. Say that now SFO is a communication ship of a fleet, using a satellite link to join the infrastructure, and that the cabs are Mobile Routers installed on smaller ships, equipped with low range radios. If SFO is also the root-MR of a nested structure of cabs, the communication between cabs is relayed by SFO and does not require the satellite link. SFO recursively terminates the nested tunnels to the cabs and reencapsulates all the packets between the nested cloud and correspondents in the infrastructure in a single tunnel to CA5A, this providing for nested NEMO Route Optimization. 7.2 Applicability This complex topology applies to large distributed fleet, mostly if there is a single interchange point with the internet (e.g. a NAT or a socks farm) where the super HA could be located. Thubert, et al. Expires April 5, 2005 [Page 14] Internet-Draft Home Network models with NEMO basic October 2004 One specific benefit is that when 2 MRs travel together with a common HA, the traffic between the 2 is not necessarily routed via the infrastructure, but can stay confined within the mobile cloud, the Mobile Home Agent acting as a rendez-vous point between the MRs. This applies particularly well for a fleet at sea when the long haul access may be as expensive as a satellite link. Thubert, et al. Expires April 5, 2005 [Page 15] Internet-Draft Home Network models with NEMO basic October 2004 8. Changes 8.1 Changes from version 00 to 01 Removed terminology (moved to the Nemo terminology draft). Added an applicability statement for all documented cases Thubert, et al. Expires April 5, 2005 [Page 16] Internet-Draft Home Network models with NEMO basic October 2004 9. Acknowledgements The authors wish to thank: Erik Nordmark, Kent Leung, Thierry Ernst, TJ Kniveton, Patrick Wetterwald and Alexandru Petrescu for their contributions. 10 References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [3] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [4] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [5] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6) Addressing Architecture", RFC 3513, April 2003. [6] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC 3753, June 2004. [7] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [8] Devarapalli, V., "Network Mobility (NEMO) Basic Support Protocol", draft-ietf-nemo-basic-support-03 (work in progress), June 2004. [9] Ernst, T., "Network Mobility Support Goals and Requirements", draft-ietf-nemo-requirements-02 (work in progress), February 2004. [10] Ernst, T. and H. Lach, "Network Mobility Support Terminology", draft-ietf-nemo-terminology-01 (work in progress), February 2004. [11] Wakikawa, R., Devarapalli, V. and P. Thubert, "Inter Home Agents Protocol (HAHA)", draft-wakikawa-mip6-nemo-haha-01 (work in progress), February 2004. [12] Ernst, T., "Analysis of Multihoming in Network Mobility Support", draft-ietf-nemo-multihoming-issues-00 (work in Thubert, et al. Expires April 5, 2005 [Page 17] Internet-Draft Home Network models with NEMO basic October 2004 progress), July 2004. Authors' Addresses Pascal Thubert Cisco Systems Village d'Entreprises Green Side 400, Avenue de Roumanille Batiment T3 Biot - Sophia Antipolis 06410 FRANCE Phone: +33 4 97 23 26 34 EMail: pthubert@cisco.com Ryuji Wakikawa Keio University and WIDE 5322 Endo Fujisawa Kanagawa 252-8520 JAPAN EMail: ryuji@sfc.wide.ad.jp Vijay Devarapalli Nokia Research Center 313 Fairchild Drive Mountain View, CA 94043 USA EMail: vijay.devarapalli@nokia.com Thubert, et al. Expires April 5, 2005 [Page 18] Internet-Draft Home Network models with NEMO basic October 2004 Appendix A. Returning Home emulation in the virtual case When a Home Link is virtual, all traffic to and from the Mobile Network is sent through the bi-directional tunnel even at the Home Link. This section describes one possible mechanism that extends NEMO Basic Support to eliminate this tunneling overhead. Although the Home Link is virtual, the Home Agent has at least one physical link to communicate with the external world. One or several of such links, called the virtual Home Access Links, are conceptually associated with the virtual Home Link and considered as part of Home. When accessing one of its virtual Home Access Links, a Mobile Router autoconfigures a Care-of Address from a Router Advertisement as it would do on any visited link, in order to perform the next binding flow. If the Mobile Router is configured to recognize the virtual Home Access Links as part of Home, it deregisters by sending a Binding update with null lifetime sourced at the CareOf. Alternatively, the Home Agent may indicate that the MR has moved to the virtual Home Access Links as a status code in the binding acknowledgement. The status code implies that Home Agent successsful de-register the binding at the virtual Home Access Link. Detection of the virtual Home Access Links is achieved by a prefix comparison(s) between the care-of address and the prefix(es) on the virtual Home Access Link(s). With both approaches, the result of the binding flow is a deregistration. Consequently, both the Mobile Router and the Home Agent disable the bi-directional tunnel. At that point, the Home Agent configures its forwarding in order to reach the Mobile Router and its mobile networks at Home. For instance, this may take the form of a route to the Mobile Network prefixes via the MR Home Address, and a connected host route to the MR Home Address via the virtual Home Access link. After successful binding de-registration, the Mobile Router MUST receive packets meant to the Mobile Router's Home Address at the Virtual Home Link. How to intercept packets addressed to the Home Address depends on implementations of the Mobile Router. If the Home Address is not configured at the egress interface, the Mobile Router MUST use proxy Neighbor Discovery to intercept all packets addressed to the Home Address on the virtual Home Link. Otherwise, the Mobile Router does not have to perform any special operation at the virtual Home Link. Thubert, et al. Expires April 5, 2005 [Page 19] Internet-Draft Home Network models with NEMO basic October 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Thubert, et al. Expires April 5, 2005 [Page 20]