System information

Upper-Layer Protocols
Book Title
11-254
control technique, where the receiver tells the sender how many messages it can accept. NSP can
also respond to congestion notifications from the network layer by reducing the number of
outstanding messages it will tolerate.
Upper-Layer Protocols
Above the transport layer, DECnet supports its own proprietary upper-layer protocols as well as
standard OSI upper-layer protocols. DECnet application protocols use the DNA session control
protocol and the DNA name service. OSI application protocols are supported by OSI presentation-
and session-layer implementations.
Troubleshooting DECnet
This section presents protocol-related troubleshooting information for DECnet Phase IV
connectivity and performance problems. The procedures outlined apply only to environments in
which DECnet routing is enabled on the router, not to environments in which DECnet is being
bridged (that is, bridging is enabled on the router interfaces and EtherType 6003 is being passed).
This chapter does not discuss other Digital protocols, such as Maintenance Operation Protocol
(MOP), local-area transport (LAT), local-area VAX cluster (LAVC), and local-area systems
technology (LAST).
Note For information about troubleshooting ISO CLNS (DECnet Phase V) problems, refer to
Chapter 12, “Troubleshooting ISO CLNS.”
The section “Using DECnet in a Multiprotocol Environment” discusses possible problems when
using DECnet in an internetwork running other protocols as well. The remaining sections describe
specific DECnet symptoms, the problems that are likely to cause each symptom, and the solutions
to those problems.
The following sections outline the most common network issues in DECnet networks:
• DECnet: Connections to DEC Hosts Fail over Router (End Node Problem)
• DECnet: Connections to DEC Hosts Fail over Router (Router Problem)
• DECnet: End Nodes Cannot Find Designated Router
• DECnet: Router or End Node Sees Incorrect Designated Router
• DECnet: Routers Not Establishing Adjacencies
• DECnet: Routing Node Adjacencies Toggle Up and Down
• DECnet: No Phase IV Connectivity over Phase V Backbone
• DECnet: Poor Performance
Note In some of the symptom discussions that follow, Operator Communication Manager
(OPCOM) messages are used to illustrate certain errors. These examples assume that OPCOM is
running and event logging is enabled. For more information about event logging, see the section
“Configuring a DECnet Node to Log DECnet Events” later in this chapter.