Routing in a network

#The invention relates to routing in a network, in particular a network to which a mobile node connects.

#FIG. 1 is a schematic illustration of a network 1 that allows wireless communication with a mobile device 5. The mobile device may be, for example, a mobile telephone or a handheld wireless device such as a BlackBerry™ device and will be referred to generally as a “mobile node” (MN).

#As is well known, a mobile node 5 may connect to the network 1 via one of a plurality of access points 4 (“AP”). Each access point has a defined area of geographic coverage and, as the mobile node 5 moves, it is “handed-off” from one access point to another when it passes from a geographic area served by one access point to the geographic area served by another access point. It is desirable that the user of the mobile node does not experience any breakdown or interruption in communication when the mobile node is handed-off from one access point to another.

#Preferred embodiments of the present invention will now be described by way of illustrative examples, with reference to the accompanying figures, in which:

#FIG. 1 is a block schematic diagram of a network architecture proposed by the IETF NETLMM working group;

#FIG. 2 is a block schematic diagram of a network architecture of the present invention;

#The invention will be described with reference to embodiments in which routing information is stored in Bloom filters. The invention is not however limited to the use of Bloom filters, and the invention may be effected by storing routing information in any data structure that is equally, or better, suited for a compact representation of set membership. For example, the invention may be alternatively effected using Approximate State Machines to store the routing information. Approximate State Machines are described by, for example, Bonomi et al., in “Beyond Bloom Filters: From Approximate Membership Checks to Approximate State Machines”, in the Proceedings of ACM SIGCOMM 2006 conference.

#FIG. 2 is a schematic block diagram showing a network 10 according to one embodiment of the present invention. In the network 10 of FIG. 2, Access Routers/Mobile Access Gateways 13a-13e belong to one NETLMM domain and Access Router/Mobile Access Gateway 13f belongs to another NETLMM domain (not shown in full in FIG. 2). Each Access Router has one or more associated Access Points (the Access Points associated with Access Routers 13a-13c have been omitted from FIG. 2 for clarity). The Access Routers of a domain have a distributed architecture, and the Local Mobility Anchor of FIG. 1 is not required.

#The distributed architecture of FIG. 2 requires that routing information is distributed among each Access Router 13a-13e of an NetLMM domain to give a distributed routing structure, implemented jointly by the Access Routers of an NetLMM domain. According to the present invention the storage and communication overheads of this approach are made tolerable through the use of Bloom Filters to store routing information. Bloom filters are a storage-efficient way of representing set membership.