RELIABLE TRANSMISSION OF DATA OVER A SEMI-FIFO ROUTING LAYER

In computer networks there is usually a trade-off between the performa nce and implementation complexity of the routing protocol, and those o f the protocol for reliable transmission of data. Often, the routing p rotocol can perform better if it is not required to retain the FIFO or der of the routed data units. However, in such a case the protocol for reliable transmission of data has to maintain many logical timers and to have accurate estimate of the round trip delay. The paper introduc es a new notion: semi-FIFO service, which means that the routing layer retains the FIFO order in part. The paper shows that sometimes a non- FIFO routing layer may provide for semi-FIFO service, without substant ial changes in the routing concept. Then, the paper proposes a new pro tocol for reliable transmission of data over an unreliable semi-FIFO r outing layer. The protocol uses only one logical timer and does not re quire an estimate of the round trip delay in order to operate with ful l capacity. Therefore, the contribution of the paper is eliminating th e deficiencies associated with non-FIFO routing schemes that may offer semi-FIFO service.