3Com CoreBuilder 7000, Руководство по эксплуатации

Страница: 150 / 264

150 C
HAPTER
7: LAN E
MULATION
V
ERSIONS
1.0
AND
2.0
Figure 50
LES and BUS Connections
Address Resolution When a LEC needs to forward a unicast data frame whose LAN
destination is not found in its local Forwarding Data Base it attempts to
locate a LEC that represents the LAN destination on the ATM network. To
do this, it turns to the LES in a process called
address resolution .
As mentioned above, the LES is the central “directory” service for
verifying LEC ATM addresses on an ELAN (see “LAN Emulation Server
(LES)” on page 140). The LEC submits an
LE_ARP (LE Address Resolution
Protocol) Request to the LES. If an LEC ATM address corresponding to the
submitted LAN destination is found in the LES table it is transmitted back
to the requesting LEC as an
LE_ARP Response. In case the requested
address is not found at the LES, the LES will forward the query to other
LECs to search the non-registered addresses and then return a positive
response back to the requesting LEC. On receipt of an LE_ARP Response
the LEC records the destination LEC ATM address together with the LAN
CoreBuilder 7000