Comtech EF Data CDM-570/L Vipersat Parameter Editor - Manual (Page 28)

Network
2-12 CDM-570/L, CDD-56X Parameter Editor User Guide
Enable SAR
Packet Segmentation and Reassembly (SAR) can be enabled for QoS. With this
feature, packets are made smaller to speed them through the network and
because of specified packet size restrictions for a given path.
SAR is an adaptive process; it will trigger only if the packet latency exceeds the
threshold value (default is 20 msec). Latency value is calculated based on the
satellite transmission bandwidth. The minimum segment size is limited to 480
bytes—excluding satellite HDLC header information—in order to avoid satel-
lite overhead and consumption of CPU cycles.
Rules Table
The Rules table appears in the lower portion of the QoS dialog. Just above the
table is a button set that acts on the table, and consists of the Add, Remove,
Modify, Up/Down Arrow, and Clear buttons. When an existing rule is
selected, that rule can be repositioned in the table listing through the use of the
Up/Down Arrow buttons. Note, however, that the Default rule always occupies
the first row of the table and can not be repositioned.
Developing QoS Rules in a VMS Network
The optional QoS capabilities available in each modem/router may be utilized
whenever a modem will be handling high-priority traffic, such as video or
voice. While developing the QoS Rules to be applied to the unit, the type of traf-
fic the modem is expected to handle must be considered.
Defining QoS Rules
The QoS mode that is chosen will determine the settable parameters for defining
QoS rules. An example of a dialog for adding a rule is shown below in
figure 2-10.
QoS Rules can be assigned to up to 32 different types of flows defined by the
user. Flows can be defined by any combination of Protocol (FTP, UDP, RTP,
etc.), Source/Destination IP (specific or range), and/or Layer 3 Source/Destina-
tion Port.