Data link layer processor system for a local exchange system

A data link layer processing (DLLP) system comprising a physical link connected to a plurality of user ports each providing a packet data on said physical link, an access network system having a first interface for multiplexing logical links on said physical link, a local exchange system having a second interface for layer 2 processing said packet data supplied through said logical links, and a transmission line for coupling said access network system and said local exchange system for implementing a part of said logical link,

• at least one of said first and second interfaces comprising a plurality of DLLPs including an in-service DLLP and a spare DLLP, a switch for switching between said in-service DLLP and said spare DLLP for connection with said transmission line said switch having a multi-coupling function for coupling said transmission line to both said in-service DLLP and said spare DLLP, said in-service DLLP transfers said logical links to said spare DLLP one by one, while frame multiplexing, said packet data from said spare DLLP with data from said in-service DLLP, said switch decoupling said in-service DLLP from said transmission line to leave said spare DLLP coupled with said transmission line for transmission of data on said plurality of logical links.