Nortel Networks 4050 manual Communication channels, About SSH

38Chapter 1 Overview

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.

Table 1 Communication channels in the Nortel SNA network

Communication	Communication protocol
Between Nortel SNAS 4050 and edge	SSH
switches
Between Nortel SNAS 4050 devices in a	TCP and UDP
cluster
Between Nortel SNAS 4050 and client PC	SSL/TLS
(TunnelGuard applet)
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

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.

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