Minimizing resource protection in IP over WDM networks: Multi-layer Shared Backup Router

This work compares two resilience strategies on multi-layer network dimensioning: dual-plane protection and Multi-Layer Shared Backup Router. Latter provides a significant reduction (up to 24%) on the required IP equipment in comparison with current approach.

Currently, MPLS survability only can be done using pre-stablished links.
Multi-layer Shared Backup Routers • Multi-layer restoration consist on using the increased DWDM layer connectivity and dynamicity to recover both layer failures.
• Multi-layer restoration allows to increase availability due to the higher number of resources to drive traffic available.

Case Study
• Table 1 shows the MTTR for protection and MLSBR schemes assuming a MTBF of 3 years.
• OPEX can be reduced using this protection scheme as MTTR is greater for the same availability.

Multi-Layer Shared Backup Router use case
MLSBR use case consists on providing backup routers, which are available in case of a node fa that there is an optical mesh connection access, transit and interconnection routers.As previou whole IP nodes must be duplicated in order to solve IP router failure.Let us assume a hierarchica three levels, as shown in Fig. 2a.In this example, the transit routers are duplicated to recover t When using MLSBR, a set of Shared Backup Routers (SBRs) are available so, when there is a fa routers, the failed transit router configuration is copied and new connections are created t interconnection nodes.This scheme is presented in Fig. 2b.To create the IP/MPLS adjacencie routers to the backup routers, a new path is requested to the optical layer using UNI.The destinat and the path to be requested via UNI is configured beforehand by the access router.The con similarly from the interconnection to the transit router.As previously mentioned, it is assume optical mesh between access and transit nodes.This is why a new back-up path can be provision happens.
Let us remark that the recovery time using dual-plane protection resilient is faster than a because MLBSR takes similar time to optical restoration.However, as demonstrated in previ network availability when using MLSBR approach is better than traditional dual-plane protection.
Table 1 shows the MTTR for protection and MLSBR schemes assuming a MTBF of 3 years in the scenario presented in Fig. 2 with seven locations for transit routers.Based on the results increasing the MTTR for the same availability.This means that OPEX can be reduced using this p

Impact on CAPEX reduction
The MLSBR concept is proved in the Core Telefónica Spanish Network (Fig. 3).This network ha exposed in the • The number of shared back-up router can vary.
• Two SBRs à 24% of savings in the number of IP ports.Single Failure: Typical Operation: Traffic is moved to backup router.
Multilayer Control: One back-up port per link (optical connection preconfigured) B. Multilayer control: One back-up port per node (dynamic optical connection provisioning) Dual-plane Protection (b) MLSBR Fig. 2. Resilience schemes in a hierarchical topology.
Fig 2a.It is composed by 6 interconnection routers (IX-Level), 14 transit routers several access nodes (AC -Level).For this study only the two upper levels has been taken in numerical results.As depicted in Fig 2b, there is no port saving in the access routers due to th Core Networks Evolution Telefónica I+D CAPEX savings• IP layer is dimension with a maximum occupation of 80% for 1+1 protection.

Table 1 :
Comparison between MLBSR and Protection in terms of MTTR (days)