
186 CHAPTER 11: DLP (DATA LINK PROTOCOL)
The International Telecommunications Union (ITU) has defined a communications
protocol in Recommendation X.25 that uses a layered architecture. This standard is
widely used around the world in most of the Public Data Networks (PDNs). The
LAPB protocol provides a reliable full-duplex service at high speed. It is also a
bit-oriented protocol, so any kind of data can travel through an LAPB device.
In TUNNEL mode the port can be connected to any kind of device's bit-oriented
protocol. This mode is not a protocol it self; there is no spoofing, instead it serves
to encapsulate the transport protocol (like Frame Relay, X.25, etc.). This special
mode is used when the device to connect to a TXPORT device, does not support
SDLC or LAPB. Figure 11-1 shows a typial use for the DLP protocol. The Banyan
servers use LAPB mode while the CTOS stations use Tunnel mode.
Frame Relay
DOWNLOAD CONFIG
MODE BACKUP NET ALARM POWER
PRISM 9111
TRANSPORT
®
DOWNLOAD CONFIG
MODE BACKUP NET ALARM POWER
PRISM 9111
TRANSPORT
®
DOWNLOAD CONFIG
MODE BACKUP NET ALARM POWER
PRISM 9111
TRANSPORT
®
BNet
BNet
VIP over
HDLC
VIP over HDLC
Unit 001
Unit 002
Banyan Server
Banyan Server
CTOS
CTOS
Figure 11-1
Typical DLP Application
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