Nortel Networks Corporation

Bruce D Keats

Peter J Barry

Guy L Grenier

Trevor D Corkum

Brian E Stanke

A method of detecting signal degrade in an ATM network, and a network element using such method are disclosed. Signal degrade at the ATM layer of the network is detected by monitoring signal degrade at the physical layer of the network. In response, ATM cells indicative of the signal degrade may be generated at the ATM layer, and protection switching may be effected. Preferably, signal degrade at the physical layer may be monitored by determining a bit-error-rate at the physical layer. ATM alarm indication signal ('AIS') cells or ATM protection switching coordination protocol ('CP') cells may be generated to effect the protection switching.

ATM protection switching method and apparatus

An modified router provides for routing of data packets in heterogeneous networks and provides particular benefit to networks that comprise network elements transmitting predominately IP messages. These modified routers may, in some instances, run software implementing portions of the OSI routing protocol and software implementing the IP routing protocol simultaneously. Further, these modified routers provide for the exchange of routing information between software implementing these two protocols. This exchange of information enables a modified router to run both protocols with limited overhead. The modified routers may initially run only the IP routing protocol and only commence simultaneous use of the OSI routing protocols if, and when, the router receives an OSI trigger (e.g., an ES-IS Hello or IS-IS Hello). On receipt of an OSI trigger, the router may determine its nearest OSI neighbors using the IP routing table. Whenever there is a change in the IP routing table or, if desired, after a specified time out period, a router running the OSI routing protocol may re-determine its nearest neighbors or cease running the OSI routing protocol.

Routing of data packets in heterogeneous networks

Networks, network elements and methods providing a name resolution protocol which performs name resolution from a flat name space, such as the TL1 name space, to an address space, such as the IP address space are provided. Request functionality involves processing a requested name by determining if the requested name is the local name or a name of a previously resolved name-to-address mapping, and if not by sending a request message to a group of network elements which have joined the group, the request message containing the requested name for which a corresponding address is required. The group of addresses might for example be a multicast group of IP addresses. The reporting functionality involves responding to requests generated as outlined above and consists of joining a group of addresses, and processing the request message containing a requested name for which a corresponding address is required by comparing the requested name with the local name, and if there is a match, to reply with a response message specifying the local address. In embodiments employing the IP address space, the network elements have a stack interface between IP packets and physical layer frames which might for example be SONET frames. The stack interface might for example be adapted to insert the IP packets in a channel defined by predetermined byte locations in the physical layer frames. In the event the physical layer frames are SONET frames, such predetermined byte locations might for example be SONET D to D overhead bytes.

Name resolution protocol, system and method for resolving a flat name space to an address space

A method of switching between groups of working and protection channels/paths in the presence of signal degrade in an ATM network is disclosed. Signal degrade is monitored on a subset of virtual paths (&ldquo;VP&rdquo;s) within a VP group or within a subset of virtual channels within a VC group. If signal degrade is detected on this subset of VPs or VCs, all VPs or VCs within the VPG or VCG are switched from a working entity to a protection entity. Network elements and software embodying such a method are also disclosed.

Growing community of inventors

Kanata, Canada

Bruce D Keats