Intel ER8100STUS - Express 8100 Router, Справочное руководство

Страница: 89 / 150

Reference.bok : Chapter09 77 Wed Apr 22 10:58:08 1998
77
Novell Routing Concept
Novell IPX Routing
Negotiation over a WAN
link
When the WAN link is initialized, the IPX WAN protocol running in the routers
at either end of the WAN Link negotiates various parameters to ensure that the
routers are communicating on the same terms. Negotiation proceeds as follows:
1. Role Determination
During this part of the negotiation, one router is designated as the ‘Slave’
and the other becomes the ‘Master’. If only one of the routers is configured
for a numbered WAN Link, this router becomes Master. If both routers are
configured for the same link type (numbered or unnumbered) the router with
the highest Internal Net Number becomes the Master.
2. Parameter Negotiation
When the roles of the routers have been determined, the Master attempts to
find a protocol (numbered, unnumbered or static) which is acceptable to
both the routers. If it succeeds, it informs the Slave of the protocol selected.
If a numbered link is selected during negotiation, the Master also informs
the Slave of the network number assigned to the link, ensuring that both
routers use the same number for the link.
The Master also informs the Slave of the delay used on the link.
IPX Watchdog Packets
Connections to a server
When a client is connected to a server, the session is registered in a table. It is a
function of the server to keep this table up to date when client sessions are estab-
lished and terminated.
Watchdog packets
When a client has not communicated with a server within a predefined time in-
terval, the server sends out a message to the client to ask if it is still connected.
This message is known as a watchdog packet. Watchdog packets can be sent by
the IPX protocol (IPX watchdog packets) or the SPX protocol (SPX keep-alive
packets—see
“Sequenced Packet Exchange (SPX)”, p. 79 ).
If a client fails to respond to a predefined number of watchdog packets, the ses-
sion is terminated at the server.