Comtech EF Data turboIP-45 - Manual (Page 17)

turboIP-45 Performance Enhancement Proxy Revision 0
Introduction CD/TURBOIP45.IOM
1–5
1.4 Selective Acceleration
Selective Acceleration implemented by the Comtech turboIP-45 is a mechanism for providing different
quality of service (QoS) for different datagrams. Selective Acceleration only applies to IPv4 datagrams
that are received on the LAN interface and forwarded to the WAN interface.
Selective Acceleration is implemented as an ordered table of rules that determine the QoS to be
provided for traffic passing through the turboIP-45. The rules have three parts: an accounting part that
specifies the location and status of the rule in the table, a filter part that matches the datagram’s passing
through the turboIP-45 to each rule, and a QoS part that determines how the data that matches the rule is
to be treated. Each rule can specify that either all packets matching the rule be dropped or the following
QoS parameters be applied:
• A priority level
• A maximum data rate (bandwidth) for all traffic matching the rule
• Whether or not to accelerate TCP sessions matching the rule (i.e., invoke SCPS-TP)
1.5 Data and Header Compression
The turboIP-45 supports header and payload compression of accelerated TCP traffic. Compression is
enabled or disabled by a global setting. If it is enabled, both header and data compression will be
attempted on all new accelerated sessions. Compression will be negotiated during the TCP connection
establishment. Therefore, even if the turboIP-45 has compression enabled, and if the peer turboIP-45
does not also have compression enabled, then the session will not be compressed.
Data compression on accelerated TCP flows will be handled on a segment-by-segment basis. The
compressibility of each segment payload will be evaluated individually and only those segments where
the impacts would be beneficial will be compressed.
If a session is to be compressed, then the segments corresponding to that session will be compressed
only if:
1. The uncompressed payload length is greater than 90 octets
and
2. The compressed length is not larger than two octets smaller than the uncompressed length.