Survivability in IP-over-WDM Networks

Introduction Multilayer network architecture is moving into IP-optimized two-layer architecture. ․ They have same level of availability : % or 5.25 minutes of downtime per year. Network availability is assured through a combination of equipment reliability and the various network survivability approaches.

Introduction (contd.) Network equipment reliability is ensured via built-in redundancy. Survivability is the ability of the network to transfer the interrupted services onto spare network capacity to circumvent a point of failure in the network. ․ Failures can involve fiber cuts and node-related failure.

Importance of survivability in IP-over-WDM networks We take an example to show the importance of survivability. ․ The blocking probability can be formulated using the Erlang B loss formula :, Where W is the number of wavelengths per link. is the offered load in each node.

Importance of survivability in IP-over-WDM networks (contd.) Default value : W=100, =70 - blocking probability before failure = 0.137% increase to 140 Erlangs. - blocking probability after failure = = 51.17%

IP-OVER-WDM ARCHITECTURE (contd.) GMPLS supports two basic network architectures : overlay and peer-to-peer. The main difference between these two models is the IP routers can see the network`s internal topology or not.

IP-OVER-WDM ARCHITECTURE -- Overlay model IP networks form the client layer where WDM networks behave as the physical transport network service provider. There are two separate control planes : one in the core optical network and the other in the LSRs.

IP-OVER-WDM ARCHITECTURE -- Overlay model (contd.) Two alternatives to interface between IP client and WDM server ․ WDM network management system (NMS) - No direct interaction between IP control and WDM control ․ User to network interface (UNI) - IP control can directly talk to WDM control through optical UNI. - Internal network-to-network interface (INNI) - External network-to-network interface (ENNI)

IP-OVER-WDM ARCHITECTURE -- Overlay model (contd.)

IP-OVER-WDM ARCHITECTURE -- Peer to Peer model The reachability information is shared between IP and WDM networks and a single routing protocol instances runs over both the IP and WDM networks. The IP and WDM networks are integrated as a single network. Tightly integration  not practical in the near term

IP-OVER-WDM ARCHITECTURE -- Peer to Peer model (contd.)