Trunk reservation with automatic alternative routing

The purpose of the study is to review the use of trunk reservation (TR) with automatic alternative routing (AAR). It is found that using TR to give incoming traffic priority over outgoing traffic on the access links can improve network performance under abnormal conditions, whilst doing no harm under normal load. The network under consideration is the UK digital main telephone network. This is a hierarchical network, the top tier of which consists of some 53 fully-interconnected digital main switching units (DMSUs). The lower tier is made up of around 500 local processors (LPs). Each LP has a pair of links (the access links) connecting it to two of the DMSUs, which are referred to as its parent DMSUs. These are usually termed the home (H) and security (S) DMSUs, since a distinction between the two must be made when routing is considered