Comtech EF Data CDM-570 - Manual (Page 448)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Appendix G MN/CDM570L.IOM
G–12
For the typical 512 kbps remote, this equates to approximately 15% processor utilization.
Therefore, when VLAN Filtering is not used, the ‘typical’ Brouter Mode installation can support
the Network Example #1 as defined here.
G.3.4.3.2 Sample Network #2 – VLAN Filtering Enabled
Sample Network #2
Characteristic
Network Size
20 remotes
Operating Mode Brouter Mode
Shared TDM Outbound 4096 Mbps
Average Return Channel Size 1024 kbps
Remote CDM-570/L-IP processor utilization in Sample Network #2 is as follows:
Without VLAN Filtering: Assuming once more that 95% of the outbound traffic is VLAN
encapsulated (5% is intended for all sites, most likely Network Service provider management
traffic), the previous analysis indicates that the processor utilization for each remote has increased
from approximately 15% to 30%. This means that most remote CDM-570/L-IP modems are now
very near, or have exceeded, their processing capacity.
With VLAN Filtering: Continuing under the assumption that 95% of the outbound traffic is
VLAN encapsulated (5% is intended for all sites, most likely Network Service provider
management traffic), the previous analysis indicates that the processor utilization for each remote
was 60% to 80% due to the VLAN packet processing in a non-filtered operating mode. However,
with VLAN hardware filtering enabled, the IP Module for each remote CDM-570/L-IP modem
processes only the VLAN destination packets. Therefore, for the Sample Network #2, the
processing load for each remote CDM-570/L-IP modem (in a properly configured network)
decreases to approximately 10% (again assuming 5% traffic is not encapsulated in VLANs). This
means that the maximum bit rate of the return channel can increase dramatically before the IP
Module exceeds its processing capacity. On average, in the Sample Network #2 defined here,
each remote would be running at approximately 25% utilization.
G.3.4.3.3 Brouter Mode with VLAN Filtering Configuration
1. Use of the VLAN Filtering feature requires operation in Large Network
Mode to support the full 12-bit VLAN IDs field.
2. A maximum of 10 VLAN ID matches are supported. Unused VLAN ID
match fields must be set to values that DO NOT match any network VLAN
IDs.
Figure G-5 shows a Brouter Working Mode, Point-To-MultiPoint network using VLAN
Filtering.
At the Hub side, the only new configuration item required for the CDM-570/L-IP Hub Modem is
to enable VLAN Filtering. When enabled, the CDM-570/L-IP Hub Modem will transfer the first
VLAN ID to the 2-byte HDLC field.