Local Area Transport (Lat) Protocol; Advertised Services; Learned Services; Group Codes - Bay Networks 5390 Administering

Network Protocols

Local Area Transport (LAT) Protocol

The Local Area Transport (LAT) protocol multiplexes low-speed user data over a high-speed local
area network (LAN). The LAT protocol bypasses the LAN's session, transport, and routing layers.
the Model 5390 implementation of LAT provides communications service management and
load-balancing over many LAT machines advertising the same named-service.

Advertised Services

Advertised services are the announcements of resources (modems, printers, etc.) that LAT machines
have available for use by the network clients. These messages are called service announcements. A
service announcement carries the name and Ethernet address of the server offering the service, along
with a current service rating. Any host that accepts session requests is a service provider. All service
providers broadcast service announcements periodically (typically once per minute).
A host can provide multiple services. When a user broadcasts a service request and there are multiple
providers of that service, the Model 5390 server logs the user onto the host with the highest service
rating.

Learned Services

Learned services are the services that a LAT machine hears and stores from the network. All services
received by a LAT machine are filtered based on the group codes in the service announcement and
the access group code of the LAT receiving machine.
Each LAT machine has a group code mask that represents the allowable groups for users of that
machine. To store a service announcement, there must be at least one group code common between
the advertising machine and the receiving machine.

Group Codes

Service providers can be assigned a LAT group code. Group codes partition the LAT network
logically into subsets. The Model 5390 server restricts clients to the assigned group code(s). Group
codes can enhance both network security and network management.
C5-8 893-741-B