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Dynamic Creation and Deletion of Source Independent Routes

IP.com Disclosure Number: IPCOM000048485D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 4 page(s) / 57K

Publishing Venue

IBM

Related People

George, FD: AUTHOR [+3]

Abstract

A procedure is described for efficient distributed management of source-independent explicit routing tables when routes are dynamically created and deleted. Overview of Solution The technique used to assign explicit route numbers (ERNs) to dynamically created routes is for each node to maintain two logical pools of ERNs for every destination. The in-use pool consists of ERNs that correspond to existing routes. The available pool consists of ERNs that do not correspond to existing routes and may be used to designate new routes. For example, if node A wants to define a new route to node B, then node A checks its available pool (for node B) for an unused number. It then uses this number to designate the new route, and moves the ERN from its available pool to its in use pool.

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Dynamic Creation and Deletion of Source Independent Routes

A procedure is described for efficient distributed management of source- independent explicit routing tables when routes are dynamically created and deleted. Overview of Solution The technique used to assign explicit route numbers (ERNs) to dynamically created routes is for each node to maintain two logical pools of ERNs for every destination. The in-use pool consists of ERNs that correspond to existing routes. The available pool consists of ERNs that do not correspond to existing routes and may be used to designate new routes. For example, if node A wants to define a new route to node B, then node A checks its available pool (for node B) for an unused number. It then uses this number to designate the new route, and moves the ERN from its available pool to its in use pool.

For this protocol, the form of each routing table (RT) entry is:

DSA ERN ERNs TG ITGs LOCAL

IN USE where DSA equals destination sub-area mode: ERN equals explicit route number.

TG equals transmission group.

ITG equals incoming transmission group.

The function of the first four fields is:

If node A receives a message destined for DSA (DSA

not equal to A) with route number ERN, it forwards the

message on TG, after changing the route number to ERNs.

The ITG field is a bit vector of k bits at a node with k incoming TGs (ITGs). The ith bit equals 1 if and only if DSA.ERN is active over the ith incoming TG. LOCAL-IN-USE equals 1 if, and only if, there is a local session using the RT entry. To free ERNs not used by active sessions (by moving them from the in- use pool to the available pool), the route deletion function is needed. If node B has an RT entry with a given DSA and ERN, with LOCAL-IN-US=0 and ITGs=00...0, then no active session uses the RT entry, and it is deleted. This is the route deletion function needed for management of dynamic RT storage. Actually, route deletion means deletion of a RT entry. Route Setup Protocol It is assumed that there is a mechanism for an "ER-SETUP" message to travel in a network from source to destination defining a new route which must be incorporated into the RTs. (see original)

Fig. 1 is an example of an ER-SETUP attempt. Node A wants to set up a route to node D. Due to other routes defined in the network, node A already has a route to node D along the desired path. Furthermore, mediate node RTs. The portion of the route already defined should be used by the new route; defining a new ERN for the same route wastes ER numbers. Thus. one possible resulting configuration (ignoring the asterisks) is: (see original)

Consider, however, the case (with asterisks) that some route A.1 is already defined to node C, and that at node C, A.1 is swapped to a different ERN (A.2)

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and sent out on a different TG. Then, node D may not use A.1 to node C, since that ERN is used. In that case, the desired route definition is shown in Fig. 3, where i is any number in the available...