Mobile Backhaul

7.1 Introduction

Network resilience is e.g. in [1] used as ‘the maintenance of both the connectivity and the quality of service (QoS) in terms of packet loss and delay during network failures.’ This introduces the key aspects: a) maintaining service when failures occur, and, in addition b) with the defined QoS.

One aspect to start with is to look into each of the backhaul protocol layers and see what they provide in the case of link and node failures. In this chapter the focus is on the protocol layers above the physical layer: Native Ethernet (Section 2), Carrier grade Ethernet (Section 3), IP (Section 4) and MPLS (Section 5).

Resilience in the access tier is discussed in Section 6. Resilience of the radio network - core network interface is a topic for Section 7.

7.1.1 Restoration and Protection

Network recovery can be divided into restoration and protection [2], [3]. Restoration relies on activation of a new path, when a failure occurs, while protection switching uses a path that is pre-configured. Both mechanisms increase resilience of the network and both alternatives are deployed with packet networks.

Figure 7.1 shows the two approaches. In the left-hand side, protection switching occurs on a preconfigured back-up path when the failure is detected. In the right-hand side, a failure causes a routing protocol to reconverge and consequently find a new active path (dashed arrow). The new path is selected with the help of a routing protocol (best path selection).

Figure 7.1