Mobile Backhaul

7.8 Summary

In the mobile backhaul, resilience to link and node failures is achieved by features that depend on the technology used. In the base station first mile access, redundant physical links are seldomly available, due to cost and difficulties in provisioning these links to the compact base station sites.

Microwave radio is the most commonly used access media for base stations. Microwave rings have traditionally provided resilience against path failures. With high capacity base station sites, capacity in the ring easily becomes an issue. In this case, the aggregation tier supports path and node resilience and individual base stations access the aggregation network with a single or few hops only.

With packet networking, IP routing can mitigate network failures by routing around a failed link or node. OSPF is a widely deployed link-state routing protocol. It is well suited for a fast recovery, as changes in link states trigger link state advertisements (LSAs) which cause a recalculation of the shortest path tree to the destination networks. This allows recovery from a link or node failure. Recovery time depends on the size of the network (in terms of links and nodes) and on the failure detection. With fast detection, subsecond recovery can be achieved. In addition to resilience that IP routing provides, MPLS supports a fast recovery by MPLS Fast re-route (FRR).

With MEF services, availability is an attribute of the service, defined in SLA and SLS (Service Level Specification). ...