Patton electronics 2701/I User Manual page 3

2.0 GENERAL IN.ORMATION
Thank you for your purchase of this Patton Electronics product.
This product has been thoroughly inspected and tested and is warrant-
ed for One Year parts and labor. If any questions or problems arise
during installation or use of this product, please do not hesitate to con-
tact Patton Electronics Technical Support at (301) 975-1007.
2.1 FEATURES
• Terminates G.703 and G.704, E1/fractional E1 service
• Available in low-cost standalone or rack-mountable versions
• n x 64 kbps data rates to 2.048 Mbps
• 10Base-T Ethernet bridge
• PPP (Point to Point Protocol, RFC 1661) with Bridge Control
Protocol (RFC 1638)
• 75-ohm dual coax and 120-ohm twisted-pair G.703 connections
• Local and remote loopback diagnostics
• Internal and G.703 network timing
• CE and BABT approvals
• 90-260VAC & 48VDC power options
• Conforms to ONP requirements CTR 12 and CTR 13 for connec-
tion to international Telecom networks
2.2 DESCRIPTION
The Model 2701/I receives channelized G.704 (n x 64kbps) or
clear channel E1/G.703 (2.048-Mbps) data from the telco's digital data
network. The Model 2701/I terminates the G.703 telco interface and
converts the data for transmission to a user-oriented 10Base-T (802.3)
Ethernet interface.
The Model 2701/I supports an integrated 10Base-T (802.3)
Ethernet port with transparent bridging capability for IP, IPX, DECnet,
NetBIOS and other layer-3 protocols. The 2701/I attaches to the LAN
and intelligently bridges data traffic to the large central site router
through the telco's leased line network. The 2701/I supports PPP (RFC
1661) and BCP (RFC 1638).
The Model 2701/I is a 10Base-T bridge that operates over
G.703/G.704 lines. It uses MAC learning and forwarding to provide
seamless LAN-to-LAN connectivity. As a result, corporate enterprises
can connect their servers to a pair of NTUs and automatically forward
data packets that are meant for the remote network. Local packets are
filtered and passed only to the local LAN.
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3.0 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 sym-
metric 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, con-
figure, and test the data-link connection; 3. A family of Network
Control Protocols (NCPs) to establish and configure different net-
work 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 con-
figure one or more network layer protocols. Once each of the net-
work 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 communications 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.
3.1 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.
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