Load Switching; Bandwidth Allocation And Load Switching By The Stdma Controller - Comtech EF Data Vipersat CDM-570 User Manual

Load Switching

The next sections describe the principles behind Load Switching and Rate
Adjustment (Step Up/Step Down).
Bandwidth Allocation and Load Switching by the
STDMA Controller
As part of normal STDMA processing, the Hub monitors the traffic levels from
each of the Remotes for which it is allocating bandwidth. This is done using the
STDMA ACK management message (table B-1) that is transmitted at the begin-
ning of each burst from the Remote. The STDMA ACK contains two metrics
that are used by the Hub:
The number of bytes received for transmission (Queued Bytes) since the last
1.
cycle.
2. The number of bytes currently waiting to be transmitted (Bytes In Queue).
These metrics are used by the Hub for three purposes:
Determine the amount of STDMA bandwidth (slot size) to allocate in the
1.
next cycle.
2. Provide statistics of the amount of activity at each Remote (Average Bytes
Received).
3. Determine if a load switch is needed.
Data
Type
Unsigned
Unsigned
Unsigned
Unsigned
A p p e n d i x A u t o m a t i c S w i t c hi n g
B -
Table B-1
Size in
Bytes
IP 4 IP address of Remote
4
4 Bytes in Queue
1
1 Dropped Buffers
STDMA ACK Message
Unit of
Description Measure
Queued Bytes Bytes
Bytes
Group Number
Packets
L o a d S w i t c h in g
Notes:
N/A Used by Remote to identify itself
Total number of bytes queued
since last cycle (includes possible
buffer overflow)
Number of bytes currently queued
N/A
Number of packets dropped (due
to limited bandwidth)
B-3