SVC routing in network with static routing tables

• US 20010010681A1
• Filed: 03/22/2001
• Published: 08/02/2001
• Est. Priority Date: 10/25/1995
• Status: Active Grant

• Current Assignee: Nutan Behki, Richard Chan, Shawn Mcallister
• Original Assignee: Nutan Behki, Richard Chan, Shawn Mcallister
• Inventors: McAllister, Shawn, Chan, Richard, Behki, Nutan
• Granted Patent: US 6,560,218 B2
• Time in Patent Office: Days
• US Class Current: 370/228
• CPC Class Codes: H04L 2012/5621 Virtual private network [VPN]; Private-network - network-interface (P-NNI)
• CPC Class Codes: H04L 2012/563 Signalling, e.g. protocols, reference model
• CPC Class Codes: H04L 45/10 Routing in connection-oriented networks, e.g. X.25 or ATM
• CPC Class Codes: H04L 45/18 Loop-free operations
• CPC Class Codes: H04L 45/20 Hop count for routing purposes, e.g. TTL
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/26 Route discovery packet
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections
• CPC Class Codes: H04Q 2213/13141 Hunting for free outlet, circuit or channel
• CPC Class Codes: H04Q 2213/13144 Searching path through number of switching stages or nodes, e.g. revertive blocking
• CPC Class Codes: H04Q 2213/13145 Rerouting upon failure
• CPC Class Codes: H04Q 2213/13146 Rerouting upon blocking/overload, rearrangement
• CPC Class Codes: H04Q 2213/13166 Fault prevention
• CPC Class Codes: H04Q 2213/13217 Cranckback in routing, trombone connection, loopback circuit
• CPC Class Codes: H04Q 2213/13272 Premature release
• CPC Class Codes: H04Q 2213/1329 Asynchronous transfer mode, ATM
• CPC Class Codes: H04Q 2213/13296 Packet switching, X.25, frame relay
• CPC Class Codes: H04Q 2213/13352 Self-routing networks, real-time routing
• CPC Class Codes: H04Q 2213/13353 Routing table, map memory
• CPC Class Codes: H04Q 2213/13399 Virtual channel/circuits
• CPC Class Codes: H04Q 3/66 : Traffic distributors

Abstract

A method is disclosed for establishing a switched virtual circuit in a digital network having network nodes with static routing tables. The static routing tables contain at least primary and alternate routing data. When a node is unable to forward a call over its outgoing primary route due to congestion or physical failure and its alternate route is the same as the route on which a call setup request arrived, it clears the call at that node and sends a crankback message to the preceding node, which responds to the crankback message to attempt to dynamically re-route the call over the alternate route stored in the routing table of the preceding node. If the attempt is unsuccessful, it sends the message back to the next preceding node and so on.

Claims

1. A method of establishing a switched virtual circuit call in a digital communications network comprising a plurality of network nodes, each network node having a local static routing tables providing next hop routing information to adjacent nodes, characterized in that said routing tables define a primary route and an alternate route to adjacent nodes;

a network node receives a setup message for the call and searches its routing table for corresponding routing information;

the node, based on the corresponding routing information, attempts to forward the setup message on the primary route;

if the primary route is not usable due to congestion or physical failure, the node then attempts to forward the setup message on the alternate route; and

if the alternate route is the same route on which the setup message is received, the node cranks the call back to a preceding node which either forwards the setup message over the alternate route defined in that node'"'"'s routing table or again cranks the call back to a further preceding node.

2. A method as claimed in

claim 1

, characterized in that cranking the call back includes sending a release message having a crankback indication from the node to the preceding node;

and, responsive to the crankback indication, the preceeding node either forwards the setup message over an alternate route, if it can do so, or again cranks the call back to another preceding node.

3. A method as claimed in

claim 2

, characterized in that the setup message and crankback indication have a predetermined lifetime to prevent continuous attempts of cranking back the call.

4. A method as claimed in

claim 3

, characterized in that the predetermined lifetime is a count of nodes that can still be visited during the call setup, said count is decremented each time the setup message is forwarded by a network node, and the call is cleared when the count reaches zero.

5. A method as claimed in

claim 2

, characterized in that said call is cleared when the release message with the crankback indication reaches the originating endpoint.

6. A method as claimed in

claim 1

, characterized in that the primary or alternate routes are not usable due to congestion or physical failure, or looping is detected.

7. A method as claimed in

claim 6

, characterized in that looping is detected when the primary route or the secondary route is the same as the route on which the setup message is received by the node.