Specifications

Operations Manual
117
A BUS is the multicast server for an ELAN. It handles all broadcast,
multicast and unknown unicast traffic. Packets to be broadcast from the LEC
are sent to the BUS. The BUS then sends the packets back to all the LECs
using the point-to-multipoint connection.
LECs also send packets with unknown destinations to the BUS. The BUS
forwards these packets to every LEC on the ELAN, including the source
LEC where the packet originated.
In the meantime, the LEC also sends an ARP request to the LES for address
resolution. After the associated ATM address is resolved, the LEC sets up a
data direct VCC to carry the traffic. After the data VCC is set up the
following data to the destination address will be forwarded via the data VCC
instead of the BUS.
LAN Emulation Configuration Server (LECS). The primary function
of the LECS is to provide LES addresses to the LECs.
The LECS implements the assignment of individual LE clients to different
emulated LANs. A LEC can either obtain the information from the LECS
using the configuration protocol, or from its own database. It assigns any
client which requests configuration information to a particular emulated LAN
service by giving the client the LES’s ATM address. This method supports
the ability to assign a client to an emulated LAN based on the client’s location
(ATM address).
It is optional for the LEC to obtain information from the LECS using the
configuration protocol. The LECS allows the LEC to configure automatically.
The LECS is also used to keep track of all the emulated LANs and the LECs
which belong to them. When a LEC is initialized, one of its first actions is to
set up a connection to the LECS. It then sends a request for its configuration,
including the ATM address of the LES it should contact to join an ELAN. The
database in the LECS would typically be initialized by the network
administrator and managed through SNMP management applications.