Survivability in IP-over-WDM Networks

Introduction Multilayer network architecture is

moving into IP-optimized two-layer architecture.

․They have same level of availability : 99.999% 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 :

w

k

k

w

k

W

0

!/

!/

, 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.)

2

3

1

- Default value : W=100 , =70

- blocking probability

before failure = 0.137%

increase to 140 Erlangs.

- blocking probability

after failure

=

= 51.17%

230.12%)-(1-1

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-- 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.)