What is Synchronous Tunnelling?
In a typical network, routers carry routable protocols from one local area network (LAN) to another, either directly or over wide area links (WAN). In some situations there is a requirement to carry protocols that are non-routable and that are carried over synchronous lines. Synchronous tunnelling is a mechanism for carrying these protocols through a network of routers over another routable protocol. The word tunnelling refers to the fact that the traffic is passed from one point in the network to another, through a tunnel between two routers. Synchronous tunnelling is normally a proprietary option in routers. No standards exist for tunnelling generalised synchronous data through a network. A synchronous protocol such as HDLC is normally supported, since this allows the router to packectise the synchronous data. An example of a situation where synchronous tunnelling might be used is to connect two Esprit statistical multiplexers. Normally the Esprit is connected over a dedicated synchr
