Comtech EF Data CDM-570 - Manual (Page 447)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Appendix G MN/CDM570L.IOM
G–11
G.3.4.3 Router Mode (Brouter Enabled) – Point-to-MultiPoint with VLAN
Matching Filters
Brouter Point-to-MultiPoint Mode with VLAN Matching Filters applies only to
CDM-570/L-IPs and CDD-564/L-IPs operating with IP Module Firmware Version
1.6.10 or later. The entire network must be configured to operate in the same
mode – either entirely configured to use VLAN Matching Filters, or entirely
configured with Filtering Disabled.
In previous network configurations, ALL remote CDM-570/L-IP modems were required to
process all VLAN packets, and then decide whether to forward or discard. In some user
applications, this could result in very high processor utilization numbers and possibly result in
‘overdriving’ the processor, thereby causing poor network performance.
The Brouter (Bridged + Router Traffic) Working Mode with VLAN Filtering is a special mode of
operation where VLAN traffic is bridged and non-VLAN traffic is routed using static route table
information. This allows the user to optimally configure the networks to ensure that the remote
modem’s IP module is not ‘overdriven’. IP Module Firmware Versions 1.6.9 and earlier do not
support the Brouter Working Mode with VLAN Filtering feature.
The sections that follow illustrate how the Brouter Working Mode with VLAN Filtering provides
optimal performance of the customer network and its CDM-570/L-IP and CDD-564/L-IP
equipment.
G.3.4.3.1 Sample Network #1 – VLAN Filtering Disabled
This case study is derived from the monitoring of user installations, based on
approximately 386 bytes per packet, over a three-year period.
Sample Network #1
Characteristic
Network Size
20 remotes
Operating Mode Brouter Mode
Shared TDM Outbound 4096 Mbps
Average Return Channel Size 512 kbps
Remote CDM-570/L-IP processor utilization in Sample Network #1 is as follows:
Without VLAN Filtering: Assuming that 95% of the outbound traffic is VLAN encapsulated
(5% is intended for all sites, most likely Network Service provider management traffic), for a
typical mix of traffic, each CDM-570/L-IP remote modem will consume approximately 60-80%
of the IP Module’s processor capacity while inspecting the VLAN packets. For the return
channels averaging 512 kbps, in most cases the additional packet-per-second processing load
keeps operations under the IP Module’s capabilities.
From cumulative test and field data, an additional 10% per processor utilization per 512 kbps has
been observed. Note that, while this is a typical number with an average of 386 bytes per packet,
traffic mixes running lower than this will observe processor utilization increase above this ratio.