GKN@SDSC.BITNET (Gerard K. Newman) (08/30/86)
From: lzaz!jmc@seismo.CSS.GOV Subject: X.25 Negotiation Date: Mon, 25 Aug 86 10:45:51 EDT There is some disagreement, at our particular site, over what OSI layer is responsible for packet size negotiation. The transport layer is the first layer which is responsible for determining frame size, and provides segmenting and blocking to meet the restrictions imposed by station/network management. The network layer also provides blocking and segmenting to meet network frame size requirements. Generally the link layer does not do blocking or segmentation. So, typically the network layer provides "efficient" frame sizes to the link layer. If the link layer has adjustable frame sizes the network layer and station/network management would be responsible for them. X.25 can be considered both as a network and a transport level service. In the context of most full-service networks X.25 provides only link level services, hiding intermediate X.25 nodes from the larger network's routing tables. In lieu of a "strong" station/network management layer the network layer would be responsible for selecting the link layer frame size. gkn --------------------------------------- Arpa: GKN%SDSC.BITNET@WISCVM.WISC.EDU USPS: Gerard K. Newman San Diego Supercomputer Center P.O. Box 85608 San Diego, CA 92138 AT&T: 619.534.5076