Much more complicated SS7 message routing Global Title Translations are required for Routing Information Request transactions between the MSCs distributed over the entire wireless carrier serving area and the two or more HLRs. As the example illustrates, the MSC routing tables quickly grow much more extensive than the STP tables. The network administration becomes increasingly complex and prone to error. The following example illustrates the issues relating to GSM network routing table administration with multiple HLRs. The STPs route SS7 messages to these HLRs based on the IMSI numbers which are usually provisioned in blocks.
Individual records take precedence over IMSI block entries.