Selective Multicast Groups; New Elan Id; New Frame Size; Llc Multiplexing For The Data Direct Vcc - 3Com CoreBuilder 7000 Operation Manual

168 C 7: LAN E V 1.0 2.0
HAPTER MULATION ERSIONS AND
Selective Multicast LANE version 2.0 has the ability to have multiple multicast groups on a
Groups particular ELAN. In LANE 1.0 there is only a single BUS which is used for
the transmission of all broadcast, unknown and multicast traffic. Every
LEC has to receive all traffic from the BUS, whether it is interested in it or
not. LANE version 2.0 allows for the establishment of multicast servers to
be established in the network in addition to the standard LANE BUS.
For example, if a user wanted to have a multicast video server on the
network it would be put into a selective multicast group. The group
would have its own Selective Multicast Server (SMS) and different LECs
could register to be members of this group when they are configured.
Only the clients who have registered to receive that video stream by
joining the multicast group would receive it. The SMS provides a MAC
layer multicast scoping function.
In the CoreBuilder 7000 registration to a multicast group is supported
through the ARP, but traffic is directed via the BUS.

New ELAN ID

In order to allow the new frame encapsulation format (described below)
to work, a new frame size and format was developed. In the new frame
size, 12 octates are added to include an ELAN ID. If frames from multiple
LECs are being multiplexed on a single VC, the device on the receiving
end of the VC need only to check the ELAN ID field to determine which
LEC to deliver the frames to.

New Frame Size

A new frame size of 1580 is supported. The ELAN and LES are defined to
have this size. Note that if a V1 LEC of a smaller frame size tries to join a
LEC of the large size it will be rejected unless the X5-Adjustment TLV is
added to its configuration and join requests. If the LANE version is
changed to 1.0, no LECs can join ELANs of 1580.
LLC Multiplexing for In LANE 1.0, each LEC creates a single data direct VC with every other
the Data Direct VCC LEC it communicates with on an ELAN. If a single edge device has
multiple LECs configured on it, and each LEC was communicating with a
similar edge device across multiple ELANs, each LEC is therefore required
to have its own data VC for each and every ELAN. If two edge devices
each had five LECs configured on them, they would require five separate
VC's to be established between them and so on.
LANE 2.0 allows a single data direct VC to be used by multiple LECs on an
edge device. Two edge devices with five LECs each would only require
one VC to be established between them. To distinguish between the