NEtwork MObility (NEMO) Houcheng Lee
Main Idea • NEMO works by moving the mobility functionality from Mobile IP mobile nodes to a mobile router. The router is able to change its attachment point to the Internet in a manner that is transparent to attached nodes
Goals – RFC4886 • Migration Transparency • Performance Transparency and Seamless Mobility • Network Mobility Support Transparency • Operational Transparency • Arbitrary Configurations • Local Mobility and Global Mobility • Scalability • Backward Compatibility • Secure Signaling • Location Privacy • IPv4 and NAT Traversal • Minimal Impact on Internet Routing
Requirements – RFC 4886 • The solution must be implemented at the IP layer level • The solution must set up a bi-directional tunnel between a MR and its HA (MRHA tunnel) • All traffic between MNN and CN msut transit through the bi-directional MRHA tunnel • MNNs must be reachable at a permanent IP address and name • The solutions must maintain continuous sessions
Requirements – RFC 4886 • The solution must not require modifications to any node other than MRs and Has • Support fixed nodes, mobile hosts, and mobile routers in the mobile network • Must allow MIPv6-enabled MNNs to use a mobile network link as either a home link or a foreign link • Must ensure backward compatibility • Solution will behave the same way if NEMO is nested.
Requirements – RFC 4886 • Arbitrary levels of recursive mobile networks must be supported • The solution must function for multihomed MRs and multihomed mobile networks as defined in RFC 4885 • NEMO support signaling over the bi-directional must be minimized • Signaling messages between the HA and the MR must be secured • The solution must ensure transparent continuation of routing and management operations over the bi-directional tunnel • When one egress interface fails, the solution may preserve sessions established through another egress interface • The solution should have a minimal impact on the global Internet routing system
Basic Support - Introduction • An extension to Mobile IPv6 (MIPv6) • compatible with Mobile IPv6 • e.g. a NEMO-compliant HA can operate as a Mobile IPv6 HA • satisfies the goals and requirements identified in “Network Mobility Support Goals and Requirements” (RFC4886) • NEMO ensures session continuity for all the nodes in the MN, even as the MR changes its point of attachment to the Internet • NEMO provides connectivity and reachability for all nodes in the MN as it moves
Basic Support - Introduction • Definition of a MR extends that of a Mobile IPv6 Mobile Node, by adding routing capability routing between its point of attachment and a subnet that moves with the MR • proposes a bi-directional tunnel between the MR and its HA. • Tunnel is set up when the MR sends a Binding Update to its HA successfully • All traffic between MNN and CN passes through the HA • Basic support does not place any restriction on the number of levels for nested mobility, but significant overhead is expected
Basic Support - Overview • A mobile Network is a network segment or subnet that can move and attach to arbitrary points in the routing infrastructure • The Mobile Router is the default gateway for the Mobile Network • A Mobile Network can comprise of nested subnets, but the overhead is heavy • A Mobile Router has a unique registered Home Address with its Home Agent. The Home Address is configured from a prefix aggregated and advertised by its Home Agent.
Basic Support - Overview • When Mobile Router acquires a Care-of Address from Foreign Agent, it sends a Binding Update to its Home Agent, and Home Agent creates a cache entry binding the Mobile Router’s Home Address to its Care-of Address. • If the Mobile Router Seeks to act as a Mobile Router and provide connectivity to nodes in the Mobile Network, it indicates this to the Home Agent by setting a flag (R) in the Binding Update • Mobile Router MAY include information about one or multiple Mobile Network Prefix in the Binding Update
Basic Support - Overview • The Home Agent acknowledges the Binding Update by sending a Binding Acknowledge to the Mobile Router. A positive acknowledgement with the Mobile Router Flag (R) set means that the Home Agent has set up forwarding for the Mobile Network. • Once the binding process finishes, a bi-directional tunnel is established between the Home Agent and the Mobile Router, and the end points of the tunnel are the MR’s CoA and HA’s address. • The packets sourced from MN are sent to HA through the reverse-tunnels which is done by using IP-in-IP encapsulation, and then HA decapsulates the packets and forward it to the CN.
Basic Support - Overview • Before MR decapsulates the packets sent from HA via tunnel, MR has to check whether the Source address on the outer IPv6 header is the Home Agent’s address, but this check is not necessary if the packet is protected by IPsec in tunnel mode. • The MR and HA can run a routing protocol through the bi-directional tunnel. In this case, the MR need not include prefix information in the Binding Update. Instead the HA uses the routing protocol updates to set up forwarding for the Mobile Network. The MR should be configured not to send any routing protocol messages on its egress interface when it is away from he home link and connected to a visited link.
Basic Support - Overview Get CoA Binding Update MR acts as Mobile Host HA create cache entry
Basic Support - Overview Get CoA Binding Update with flag (R) MR acts as Mobile Router HA implicit mode – No Network Prefix Option in the Binding Update explicit mode – include one or more (multiple prefix information options on) Mobile Network Prefix Options
Basic Support - Overview Binding Acknowledgement set to 0 (Binding Update accepted) MR HA with Mobile Router Flag (R) once finishes, a bi-directional tunnel is established MR’s CoA HA’s address
Basic Support - Overview src address from Mobile Network reverse-tunnels MR HA using IP-in-IP encapsulation decapsulates and forward CN
Basic Support - Overview MNN decapsulates and check (for Security Considerations) 1. src address is HA’s address (NOT necessary if IPsec) 2. inner IPv6 header belongs to a prefix used in MN DROP MR HA tunnel MR CoA CN
Basic Support - Overview Dynamic Routing Protocols run an intra-domain routing protocol (e.g RIPng and OSPF) through the bi-directional tunnel MR HA HA uses the routing protocol updates to set up forwarding for the MN MR should be configured NOT to send any routing protocol messages on its egress interface
Basic Support – Message Formats • Binding Update • A new flag (R) (Mobile Router Flag) is included in the Binding Update to indicate to the HA whether the Binding Update is coming from a MR not from a mobile node • Other Mobility options are defined in RFC3775 “Mobility Support in IPv6”
Basic Support – Message Formats • Binding Acknowledgement • A new flag (R) is included in the Binding Acknowledgement to indicate that the Home Agent that processed the corresponding Binding Update supports MR • New Binding Acknowledge status values • 140 Mobile Router Operation not permitted • 141 Invalid Prefix • 142 Not Authorized for Prefix • 143 Forwarding Setup failed (prefixes missing)
Basic Support – Message Formats • Mobile Network Prefix Option • The Mobile Network Prefix Option is included in the Binding Update to indicate the prefix information for the MN to the HA. An alignment of 8n+4 is required.
Basic Support – MR Operation • MN can act in 2 ways • Mobile Host • HA doesn’t maintain prefix information related to MH • maintain a cache entry related to the MH’s Home Address • Mobile Router • both prefix information and cache entry are maintained • Mobile Router Flag (R) is used to represented these 2 modes • MR maintains a Binding Update List. It is one entry per each destination to which MR sending Binding Updates
Basic Support – MR Operation • Sending Binding Updates • if MR is not running a routing protocol, 2 modes are used to tell HA which prefixes belong to the MR • Implicit: MR does not include a Mobile Network Prefix Option in the Binding Update. HA uses other mechanism to determine the Mobile Network Prefix(es) owned by the MR • Explicit: MR includes one or more Mobile Network Prefix Options in the Binding Update • if the Mobile Router Flag is set, the Home Registration Flag (H) must be set
Basic Support – MR Operation • Receiving Binding Acknowledgements • 0 (Binging Update accepted) and the Mobile Router Flag (R) is set to 1 • If (R) not set, MR assumes that HA doesn’t support Mobile Routers • Then MR performs Dynamic Home Agent Address Discovery again to discover HA that supports • MR MUST de-register with the HA before attempting registration with another • Status of Binding Acknowledgement status is set to a value between 128 and 139
Basic Support – MR Operation • Establishment of Bi-directional Tunnel • After a successful Binding Acknowledgement is received, the MR sets up its endpoint of the bi-directional tunnel • The bi-directional tunnel is created by merging 2 unidirectional tunnels as described in RFC2473 • CoA of MR and HA’s address are the two ends of the bi-directional tunnel • A MR uses the Tunnel Hop Limit normally assigned to routers (RFC2473)
Basic Support – MR Operation • Neighbor Discovery for Mobile Router • When the MR is at home, it MAY be configured to send Router Advertisements and to reply Router Solicitations on the interface attached to the home link • The value of the Router Lifetime field SHOULD be set to 0 to prevent other nodes from configuring the MR as the default router • MR SHOULD NOT do any of the above when on the visited link • MR MUST NOT ignore Router Advertisements received on the egress interface. The received Router Advertisements MAY be used for address configuration, default router selection, or movement detection
Basic Support – MR Operation • Multicast Groups for Mobile Router • When at home, the MR joins the multicast group All Routers Address with scopes 1 interface-local (on the home-advertising interface), and 2 link-local, on any of it egress interface. • When in a visited network, MR MUST NOT join the above multicast groups
Basic Support – MR Operation • Returning Home • When returning home, MR MUST de-register with its HA • MR MUST implement and follow the returning-home procedures defined for a mobile node in RFC3775 • MR might start behaving as a router on its egress interface • MR may send Router Advertisement but the lifetime should be set to 0 to prevent being picked as a default router • MR may join the All Routers Address multicast group • MR may send routing protocol messages on its egress interface if it is configured to run a dynamic routing protocol • When the HA removes a binding cache entry, it deletes all associated Mobile Network Prefix routes
Basic Support – HA Operation • HA MUST satisfy all the requirement listed in section 8.4 of RFC 3775 • Data Structure • Binding Cache • HA maintains Binding Cache Entries for each MR currently registered with the HA • might also need to store Mobile Network Prefixes associated with a MR in the corresponding Binding Cache Entry • HA also stores the status of the Mobile Router Flag (R) in the Binding Cache entry
Basic Support – HA Operation • Prefix Table • HA should prevent a MR from claiming Mobile Network Prefixes belonging to another MR • HA maintains a Prefix Table and verifies the prefix information provided by the MR against Prefix Table entries • Not required if running a dynamic routing protocol • In explicit mode, Prefix Tables are used by Has when they process Binding Updates • Each entry contains: • The Home Address of the Mobile Router • The Mobile Network Prefix of the MR associated with HA
Basic Support – HA Operation • Mobile Network Prefix Registration • The HA processes the Binding Updates as described in section 10.3.1 of RFC 3775 • The Home Registration (H) Flag MUST be set • Relaxes RFC 3775 requires that the HA in the Binding Update be configured from a prefix advertised on the home link, but rejects the Binding Updates only if the HA does not belong to the prefix that the HA is configured to serve • Check if there is a duplicated one in cache entry, otherwise send acknowledgement with code 139
Basic Support – HA Operation • Advertising Mobile Network Reachability • To receive packets meant for the Mobile Network, the HA advertises reachability to the Mobile Network • If the Home link is configured with an aggregated prefix and the Mobile Network Prefix is aggregated under that prefix, then the routing changes related to the Mobile Network maybe restricted to the Home link • If the HA receives routing updates through a dynamic routing protocol from the Mobile Router, HA can be configured to propagate those routes on the relevant interface
Basic Support – HA Operation • Establishment of Bi-directional Tunnel • Must be capable of the following operations: • HA can tunnel packets meant for the Mobile Network prefix to the Mobile Router’s current location, the CoA • The HA can accept packets tunneled by the Mobile Router with the src address of the outer IPv6 header set to the Mobile Router’s CoA
Basic Support – HA Operation • Forwarding Packets • when HA receives a data packets destined for the MN, it MUST forward the packet to the MR through the bi-directional tunnel • Utilize the routing table, the Binding Cache or a combination to route packets to the Mobile Network • Two examples • HA maintains a route to the MN Prefix with the next hop set to the MR’s HA • HA maintains a route to the MN Prefix with the outgoing interfaces set to the bi-directional tunnel interfaces
Basic Support – HA Operation • Sending Binding Acknowledgements • HA sets the status code in the Binding Acknowledgement to 0 (accepted) • code 140 means HA is not configured to support Mobile Routers • code 141 means one or more prefixes received in the Binding Update are invalid • code 142 means not authorized to use this Home Address to forward packets • code 143 means Forward Setup failed
Basic Support – HA Operation • Mobile Network Prefix De-registration • HA deletes the Binding Cache Entry for the MR’s Home Address and stops proxying the Home Address • HA removes the bi-directional tunnel and stops forwarding packets to the Mobile Network.
Basic Support – Modification to Dynamic Home Agent Address Discovery • Extends the Dynamic Home Agent Address Discovery (DHAAD) defined in RFC 3775, so that MR only attempts registration with HA that support them • Modified Dynamic Home Agent Discovery Address Request • Modified Dynamic Home Agent Discovery Address Request • Modified Home Agent Information option
Basic Support – Support for Dynamic Routing Protocols • An alternative way to set up the forward between HA and MR is run an intra-domain routing protocol such as RIPng and OSPF through the bi-directional tunnel. • So the MR can continue running the same routing protocol that it ran when attached to the home link.
Basic Support – Support for Dynamic Routing Protocols • This feature is useful. Routing changes can propagate to HA and MR quickly • When the MR returns to the home link, it runs a routing protocol by sending routing updates through its egress interface, and stop sending routing updates when in a visited link.
Home Network - Introduction • In NEMO, the Home Network can encompass much more than the Home Link • Home Network can spans the Home Link and all the Links that the MRs carry with them • Provided examples aim at illustrating the NEMO Basic Support • Five different organizations of the Home Network
Home Network - Introduction • MIPv6 Home Network • the Home Network is with Mobile IP • NEMO Extend Home Network • the Home Network only subnet of a larger aggregation that encompasses the Mobile Networks. • When at home, a Mobile Router performs normal routing between the Home Link and the Mobile Networks
Home Network - Introduction • NEMO Aggregated Home Network • the Home Network overlaps with the Mobile Networks • When at home, a MR acts as a bridge between the Home Link and the MNs • Virtual Home Network • No physical Home Link for the MRs to come back home
Home Network - Introduction • NEMO Mobile Home Network • A global Home Network is advertised to the infrastructure by a head Home Agent (HA) and further subnetted into MNs • Each subnet is owned by a MR that registers it in a NEMO fashion while acting as a Home Agent for that network. • In all cases, the Home Agents collectively advertise only the aggregation of the MNs. The subnetting is kept within the Has and the MRs, not to advertised by means of routing protocols to other parties
Home Network – General Expectations • 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