User Guide

38 Chapter 1 Overview
320818-A
Communication channels
Communications between the Nortel SNAS 4050 and key elements of the Nortel
SNA solution are secure and encrypted. Table 1 shows the communication
channels in the network.
Telnet or SSH can be used for management communications between remote PCs
and the Nortel SNAS 4050 devices.
About SSH
The Secure Shell (SSH) protocol provides secure and encrypted communication
between the Nortel SNAS 4050 and the network access devices, and between
Nortel SNAS 4050 devices and remote management PCs not using Telnet.
SSH uses either password authentication or public key authentication. With public
key authentication, pairs of public/private SSH host keys protect against “man in
the middle” attacks by providing a mechanism for the SSH client to authenticate
the server. SSH clients keep track of the public keys to be used to authenticate
different SSH server hosts.
SSH clients in the Nortel SNA network do not silently accept new keys from
previously unknown server hosts. Instead, they refuse the connection if the key
does not match their known hosts.
Table 1
Communication channels in the Nortel SNA network
Communication Communication protocol
Between Nortel SNAS 4050 and edge
switches
SSH
Between Nortel SNAS 4050 devices in a
cluster
TCP and UDP
Between Nortel SNAS 4050 and client PC
(TunnelGuard applet)
SSL/TLS
Between Nortel SNAS 4050 and SREM SSH
From edge switch to EPM SNMPv3 Inform
From EPM to edge switch Telnet over SSH
From authorized endpoint to DHCP server UDP