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Compact mDSL Modem
PPP Operational Background
PPP is a protocol used for multi-plexed transport over a
point-to-point link. PPP operates on all full duplex media, and is
a symmetric peer-to-peer protocol, which can be broken into
three main components: 1. A standard method to encapsulate
datagrams over serial links; 2. A Link Control Protocol (LCP) to
establish, configure, and test the data-link connection; 3. A family
of Network Control Protocols (NCPs) to establish and configure
different network layer protocols.
In order to establish communications over a point-to-point
link, each end of the PPP link must first announce its capabilities
and agree on the parameters of the link’s operation. This
exchange is facilitated through LCP Configure-Request packets.
Once the link has been established and optional facilities
have been negotiated, PPP will attempt to establish a network
protocol. PPP will use Network Control Protocol (NCP) to
choose and configure one or more network layer protocols.
Once each of the network layer protocols have been configured,
datagrams from the established network layer protocol can be
sent over the link. The link will remain configured for these com-
munications until explicit LCP or NCP packets close the link
down, or until some external event occurs.
The PPP Bridging Control Protocol (BCP), defined in RFC
1638, configures and enables/disables the bridge protocol on
both ends of the point-to-point link. BCP uses the same
packet exchange mechanism as the Link Control Protocol
(LCP). BCP is a Network Control Protocol of PPP, bridge
packets may not be exchanged until PPP has reached the
network layer protocol phase.
Applications
In situations where a routed network requires connectivity
to a remote Ethernet network, the interface on a router can
be configured as a PPP IP Half Bridge. The serial line to the
remote bridge functions as a Virtual Ethernet interface, effec-
tively extending the routers serial port connection to the
remote network. The bridge device sends bridge packets
(BPDU's) to the router's serial interface. The router will
receive the layer three address information and will forward
these packets based on its IP address.
Figure 1 shows a typical Cisco router with a serial interface
configured as a PPP Half Bridge. The router serial interface uses
a remote device that supports PPP bridging to function as a node
on the remote Ethernet network. The serial interface on the
Cisco will have an IP address on the same Ethernet subnet as
the bridge.
Compact mDSL Modem
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General Information
Thank you for your purchase of this Black Box product. This product has
been thoroughly inspected and tested and is warranted for One Year parts and
labor.
Features
• Provides MAC Level Data Link (Layer 2) connection between two peered
10BaseT Ethernet LANs
• Operates transparently to higher level protocols such as TCP/IP, DECnet,
NETBIOS and IPX
• PPP (Point to Point Protocol, RFC 1661) with Bridge Control Protocol
(RFC 1638)
• Automatically learns, loads and removes MAC addresses
• Point-to-Point Connectivity over 2-Wire mDSL up to 10km
• Plug-and-Play Slave
• HTTP/SNMP Manageable as CP (Customer Premises) Unit with mDSL
CO (Central Office) Rack Card
• Internal or receive recovered clocking between units
• LED indicators for 10BaseT Link, DSL Link, Status, No Signal, Error and
Test Mode
Description
The
Compact 10BaseT mDSL Modem
is a Multi-Rate DSL Modem that
provides seamless MAC Layer connectivity between 2 peered 10BaseT LANs.
Now, Enterprise users no longer need to hassle with a bridge
and
a CSU/DSU
or recurring leased line costs. The Compact mDSL Modem allows users to
add additional nodes to a LAN that has reached its maximum distance limits or
separate high traffic areas of a LAN. The Compact mDSL Modem connects
peered LANs and automatically forwards and receives LAN broadcasts, multi-
casts and frames across a 2-Wire DSL span.
The
Compact mDSL Modem sup-
ports PPP (RFC 1661) and BCP (RFC 1638).
The
Compact 10BaseT mDSL Modem
features include loopback diag-
nostics, inband SNMP/HTTP remote management capabilities using Plug-and-
Play and externally accessible configuration switches. As a symmetric DSL
modem, the
Compact mDSL Modem
offers the same data rates in both direc-
tions over a single pair of regular telephone lines using Carrierless Amplitude
and Phase (CAP) modulation. The Compact mDSL Modem connects to the
DSL line via an RJ-45 jack. Standard power options include 115VAC, 230VAC,
Universal (115/230VAC) and any DC input between 36-60VDC.
