Lantronix ETS Reference Manual - page 24
LAT
Concepts
2-6
In general, all services offered by the ETS are associated with one or more ports; exceptions to this rule will
be noted later. Figure 2-2 shows an example of services offered on a network.
Figure 2-2: Example of Network Services
Nodes advertise their services to the network by broadcasting occasional messages about them. These
messages, referred to as multicasts, contain the node’s name and its list of services. By monitoring
multicast messages, all hosts on the network know what nodes and services are available and can provide
this information to their interactive users. The Show Services and Show Nodes commands display this
information.
LAT multicast messages contain a rating for each service offered. Ratings range from 0 to 255; 0 means
the service is unavailable, while 255 means the service is available and has no current users. Ratings for a
given service may change over time. For example, the rating for a computer accepting logins will generally
change as its workload changes. Conversely, ratings for a modem are typically either 0 (in use) or 255 (not
in use). In the example above, the server with eight modems attached will continue to advertise that the
service “modem” is available (a 255 rating) until all eight modems are in use (a 0 rating).
Service ratings may concern even casual users, since they are used to determine which service a user will
be connected to whenever there is a choice. For example, if a user types
Connect Hub
and five nodes
offer service hub, the user will be connected to the least busy node automatically. In the case mentioned
above, where both the local ETS and a remote node offered the same service, the ratings determine which
node will service the connection attempt.
Another major network management feature of LAT is the concept of service groups. Each port on the ETS
and each service on the network can be thought of as belonging to one or more groups. When a user or
device requests a service connection, the LAT host will check to see if the groups to which the requester
belongs match those of the requested service. If any group number is common to both the requester and the
service, the connection attempt continues. If there are no common group numbers, the connection attempt
fails.
Note:
There may be additional access restrictions on the service, such as password
protection.
Node Vax2, with
service Vax2
(logins to other
users)
Node Phred, a computer
offering services
"LaserPrinter" (for
printing) and "Phred"
(for logins)
Node Server_1, offering
service "modem"
0
1
PWR
OK NET RCV XMT
EPS4
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