Comtech EF Data CDM-840 - Manual (Page 211)

CDM-840 Remote Router Revision 2
Appendix D MN-CDM840
D–5
The supported refresh rates are based on the runtime characterization that there will be, at
most, 600 packets seen between refreshes. Additionally, even though the runtime supports
64,000 Tx compression sessions, it is only necessary to have context storage for a small number
over those 600 packets. Based on this specification, the CDM-840’s compression performance is
defined in Table D-3 (±5% with different compression refresh rates).
Table D-3. Compression Performance
Packet Size
% Savings per Compression Refresh Rate
1 25 50 300 600
40 23% 50% 53% 53% 55%
420 40% 51% 51% 51% 51%
800 46% 53% 53% 53% 53%
1200 49% 54% 54% 53% 54%
1472 50% 55% 55% 55% 55%
While some compressed header traffic can be lost during deteriorated satellite link
conditions, the CDM-840 tries to minimize that when Adaptive Coding and
Modulation (ACM) is enabled (Figure D-3). Sending a full packet allows the return
of the traffic stream; you may increase the Refresh Rate (smaller value) when poor
satellite link conditions are prevalent or, conversely, decrease the rate (larger
value) under clear sky condition operations.
Figure D-3. Configuration | WAN | MOD | ACM page