Table of Contents
Advertisement
DM240-DVB High-Speed Digital Modulator
User Interfaces
4.9.7 RLLP Summary
The RLLP is a simple send-and-wait protocol that automatically re-transmits a packet
when an error is detected, or when an acknowledgment (response) packet is absent.
During transmission, the protocol wrapper surrounds the actual data to form information packets.
Each transmitted packet is subject to time out and frame sequence control parameters, after
which the packet sender waits for the receiver to convey its response. Once a receiver verifies
that a packet sent to it is in the correct sequence relative to the previously received packet, it
computes a local checksum on all information within the packet excluding the <SYN> character
and the <CHECKSUM> fields. If this checksum matches the packet <CHECKSUM>, the receiver
processes the packet and responds to the packet sender with a valid response (acknowledgment)
packet.
The response packet is therefore either an acknowledgment that the message was received
correctly. If the sender receives a valid acknowledgment (response) packet from the receiver, the
<FSN> increments and the next packet is transmitted as required by the sender.
If an acknowledgment (response) packet is lost, corrupted, or not issued due to an error and is
thereby not returned to the sender, the sender re-transmits the original information packet; but
with the same <FSN>. When the intended receiver detects a duplicate packet, the packet is
acknowledged with a response packet and internally discarded to preclude undesired repetitive
executions. If the M&C computer sends a command packet and the corresponding response
packet is lost due to a system or internal error, the computer times out and re-transmits the same
command packet with the same <FSN> to the same receiver and waits once again for an
acknowledgment.
4.9.8 DM240 Opcode Command Set
Refer to Appendix A for Modem Remote Communications.
4.10 Ethernet Port User Interface
The Ethernet Port of the DM240 allows for complete control and monitoring of all DM240
parameters and functions via a 10 Base-T or 100 Base-T Ethernet Connection.
4.11 Simple Network Management Protocol (SNMP)
Simple Network Management Protocol (SNMP), as its name suggests, is a relatively simple
protocol by which management information for a network device may be inspected and/or altered
by remote administrators.
TM083 – Rev. 3.0
4-23
Advertisement
Table of Contents
