Specifications

LAN Emulation
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SNMP is defined by RFC-1157 and published by the Internet Engineering
Task Force. Full details of the ATM UNI MIB and of generic SNMP are
beyond the scope of this publication. The essential parameters are, however,
as follows:
❑ Physical layer type (SONET), medium (UTP, fiber, coaxial cable and
more), unique index number, status (normal or looped) and relevant
specifications.
❑ Number of ATM virtual paths and connections allowed. Numbers
active. How much of each address field is being used.
❑ ATM statistics: cells received, sent or dropped. Traffic descriptors and
the values that define the Sustainable Cell Rate, burst tolerance,
quality of service and more.
❑ MIB-II system group values that are required. This includes the
length of time since the last reset.
Note that while a unique LES and BUS pair must exist for each ELAN/
VLAN, only one LECS is required in the network itself.
Connections
Each LEC has separate VCCs to control address resolution requests and
data traffic. While each VCC carries traffic for only one ELAN, the VCCs
form a mesh of connections between the LECs and the other LANE entities
including the LECS, LES and the BUS.
Control
Connections
LEC ↔ LECS. A Configuration Direct VCC is a bi-directional VCC set up
by the LEC to be used to obtain configuration information such as the
address of the LES.
LEC ↔ LES/LEC ← LES. A Control Distribute VCC means VCCs will be
set up between a LEC and a LES. First, the LEC sets up a bi-directional
point-to-point VCC to the LES for sending control frames. In turn, the LES
may optionally set up a unidirectional point-to-point or point-to-multipoint
VCC for distributing control traffic from LES to LEC.
Data Connections Data VCCs are used to carry data frames between LECs or between an LEC
and the BUS. These carry data frames as well as flush messages. Apart from
flush messages, data VCCs never carry control traffic.
LEC ↔ LEC. A Data Direct VCC is set up to carry the unicast frames
between two LECs. When there are data packets to send, but the ATM
address of the destination MAC address is unknown, the LEC will forward
the packets to the BUS to broadcast them to all devices in the ELAN and, in
the meantime, query the LES of the ATM address for the destination
address.