IBM 8285 Nways, Installation And User Manual

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Centralized LES/BUS
The ATM Workgroup Switch LAN servers are centralized, such that each emulated LAN belongs to only
one LES/BUS. Distributed, or multiple, emulated LAN servers are not yet standardized.
The LAN emulation function translates LAN (MAC) addresses to ATM addresses, and performs broadcast
and multicast LAN services.
While the ATM Workgroup Switch does support two separate emulated LANs, the two emulated LANs
cannot communicate directly with each other; a router or bridge is required. This configuration is not
currently recommended.
If desired, you can disable the LAN emulation functions of the ATM Workgroup Switch and use ‘external’
LAN emulation servers, attached, for example, to an 8260 hub.
Integrated LAN Emulation Components
LAN Emulation Server (LES)
The LES provides control and address resolution functions.
Broadcast and Unknown Server (BUS)
The BUS provides broadcast and multicast functions.
No separate configuration commands are required to start the BUS, as it is started automatically
when starting the LES.
LAN Emulation Client (LEC)
An integrated ‘Lite’ LAN Emulation Client is also provided in the Control Point, which allows TFTP,
TELNET and SNMP functions to be run over an 802.3 or Ethernet V.2 (DIX) emulated LAN. This
client may work with the integrated LES/BUS or with an external ATM Forum compliant LES/BUS.
The maximum length of PING and TELNET messages depends on the maximum SDU size
supported on the corresponding emulated LAN. Table 2 lists the correspondence (in bytes):
Table 2. Maximum PING and TELNET Lengths
Maximum SDU -
802.3 ELAN
Maximum Length PING -
802.3 LEC
Maximum Length PING -
DIX LEC
1516 1492 1500
4544 4520 4528
9234 9210 9218
18190 18166 18176
Chapter 1. Introduction to the IBM 8285 Nways ATM Workgroup Switch
15