Effect of out-of-sequence frames on LLC Type 2 applications

An experimental prototype network was built to study the issues in interconnecting SNA token ring networks using packet-switched services. In particular, the effect of out-of-sequence frames on the Logical Link Control Type 2 (LLC-2) protocol was considered. LLC-2 is the link level protocol used in SNA token rings. The authors show that, if LLC-2 acknowledgement frames are out of sequence, then the logical link and the session(s) will be reset. Terminal access to hosts is not affected if the window size is one and the acknowledgement timer is set to match the wide area network (WAN) maximum packet lifetime. For application-to-application communications, other solutions are proposed and analyzed because the window one solution limits the performance of the applications.<>