1-Meg Modem Service Supported Protocols; Dbic - Nortel DMS-100 Series Maintenance Manual

4-8 Signaling for RLCM

1-Meg Modem Service supported protocols

The 1-Meg Modem Service uses several protocols to carry data from the
subscriber to the service provider. The following figure illustrates the
1-Meg Modem Service architecture.
1-Meg Modem Service architecture
10BaseT
or
100BaseT

DBIC

DBIC
The following section describes the protocols used by the DBIC, xLC,
subscriber loop, and 1-Meg Modem.
Ethernet
The DBIC has a half-duplex Ethernet interface on the network side. The
DBIC stores downstream frames and transmits the frames to the user. The
DBIC only sends frames with MAC addresses that match the MAC
addresses of the active users. Similarly, the DBIC stores frames from the
user side. The DBIC sends these frames to the network when it receives the
whole frame.
The DBIC sends all user traffic out at the Ethernet port. The DBIC does not
route traffic between users. This method has the following advantages.
The 1-Meg Modem Service does not process data above Layer 2. The
1-Meg Modem Service remains at the MAC layer and only uses the Ethernet
address. Since the DBIC does not look at the payload carried in the Ethernet
frames, except for ARP and BOOTP messages, the DBIC can carry Layer 3
data, such as internet protocol (IP), Internet Packet Exchange (IPX), and
Appletalk. However, 1-Meg Modem Service only supports TCP/IP. The
1-Meg Modem Service can support other protocols, such as IPX, if MAC
translation is turned off. When you turn MAC translation off, you reduce
297–8351–550 Standard 04.01 August 1999
LCM Line Drawer
xLC
Back
xLC
plane
xLC
makes sure that all traffic goes to the correct service provider
reduces the bandwidth overhead for broadcasts
improves network security
1280 kbit/s
2w loop
1-Meg
Modem
320kbit/s
10BaseT