Providers of Media Access Failover Solutions.

MTN NS is pleased to offer greater levels of network reliability through failover services. Failover mandates that a secondary network link be configured on alternate access media to carry data traffic to and from the branch in the event that the primary link fails.

With this added resilience, MTN NS customers are ensured of uninterrupted, seamless communications, allowing their business to continue operations unhindered should any network failures occur.

Many Means of Accessing a Service

MTN NS has developed a core network that distinctly separates its network, access, signalling, control and services functions. This means that VPN services can be deployed regardless of the network access media: 3G/HSDPA; ADSL; Wireless; MTN’s owned fibre optic cable and Diginet (via Telkom).

Greater Reliability

The ability to connect to varied access media also ensures that MTN NS are able to offer resilient services. However the degree of resilience depends on the suite of networks selected. The MTN mobile (GSM) network for example runs on a completely separate infrastructure to that of ADSL or Diginet. This architecture therefore has the highest potential for ensuring a resilient solution. Whereas the ADSL network is in some ways separate to the Diginet network, these networks very often share the same local telkom exchange and, in places, the same core infrastructure. This architecture therefore has a slightly lesser degree of true resilience.

Performance of the particular failover solution is also dependent on the quality of the primary and secondary networks. There are no guarantees on the ADSL or the GSM data networks in terms of availability, throughput, latency and packet loss from the relevant incumbant providers. These are, to a large extent, best-effort services. Depending on the number of users sharing an ADSL exchange or a particular GSM cell, performance on either of these networks can therefore vary.

How it Functions

Figure 1 : Graphical Depiction of Failover

There are two basic architectures for failover and in each of these we use a Cisco 1841 router with additional line interface cards to access the designated redundant network. The router is configured with primary and secondary routes and as a default will send all traffic to the primary route.

Should the primary route (red) become unavailable (in the event of a failure for instance) then all traffic is sent to the secondary route (blue).

The two architectural options for failover include:

1. Diginet to GSM

Figure 2 : Graphical Depiction of Diginet to GSM Failover

2. Diginet to ADSL

Figure 3 : Graphical Depiction of Diginet to ADSL Failover

Support

All these services are manned by the MTN support desk who will respond to a failure on the primary or secondary (or both) circuits and will manage the trouble ticket until both interfaces are once again stable. However, due the nature of the ADSL and GSM networks, only services running on the Diginet network attracts an SLA.