session
Glossary
Glossary-8
session
Any connection to a network service. The network service can be an
interactive login to a LAT or TCP/IP host, a connection to a modem on the
Server or another server, or something else. Users on the Server can have more
than one session active at one time, allowing them to quickly switch between
hosts or connections.
Sessions are kept in a list, and can be switched with the Forward and Backward
commands. They can be listed with the Show Session command. There is an
absolute limit of eight sessions per port on the Server; this limit can be lowered
with the Set Server Session and Set Port Session commands.
SLIP
Serial Line Internet Protocol. SLIP runs TCP/IP over serial lines allowing
hosts to dial into the Server via modems, for example, and run TCP/IP
connections to the Server’s attached Ethernet network. The Server in this case
routes packets between the serial lines and the Ethernet, making connections
to all the hosts transparent to the user. Since the serial line is actually carrying
network packets and not plain keyboard data, there is no way to return to the
Server Local> prompt without closing the SLIP session and re-logging into the
server.
SNMP
Simple Network Management Protocol. SNMP allows a TCP/IP host running
an SNMP application to query other nodes for network-related statistics and
error conditions. The other hosts, which provide SNMP agents, respond to
these queries and allow a single host to gather network statistics from many
other network nodes. The Server provides this SNMP agent only; it cannot
generate queries to other hosts. It only responds to them.
subnet mask
A “filter” that tells the Server whether a node is on the local network or a
remote network. The ETS supports Telnet connections across networks
through the use of gateways, using gateway hosts to forward messages across
network boundaries. The ETS uses the subnet mask as a filter; if the ETS’s IP
address and the remote IP address appear the same after the filter, the remote
host is assumed to be on the same local network. Otherwise, the gateway is
used.
The mask itself is a list of bits that should be enabled in the result—a 1 in the
mask means to let that bit in the IP address through, and 0 means do not. For
example, address 192.1.2.22 with mask 255.255.0.0 becomes 192.1.0.0. For
network purposes, host 192.1.5.12 is on the same network, based on the mask
specified. In this case, a gateway would not need to be accessed. A host at
192.8.12.34 would be considered as part of a different network, however, since
the network mask comes out to be 192.8.0.0 which does not match the previous
two masks. In this second case, the gateway host would be used—if it had not
been defined, the connect attempt would fail.
If the subnet mask is not set explicitly with the Set/Define Server Subnet
Mask command, the ETS will assume a mask based on its IP address and thus
the apparent network type. This mask will be 255.255.255.0 for most 19x.x.x.x
and 2xx.x.x.x IP addresses.
