Comtech EF Data turboIP-G2 - Manual (Page 34)

turboIP-G2 Performance Enhancement Proxy Revision 2
Introduction CD-TURBOIP-G2
1–12
• 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).
1.2.4.4 Data and Header Compression
The turboIP-G2 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-G2 has compression
enabled, and if the peer turboIP-G2 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:
• The uncompressed payload length is greater than 90 octets, and
• The compressed length is not larger than two octets smaller than the uncompressed
length.
1.2.4.5 Minimum Compression Ratio
The compression ratio is defined as the ratio of the sum of the sizes of all TCP segments in an
uncompressed session to the sum of the sizes of the TCP segments if that same session were
compressed. Note that this is different from the definition used in the compression ratio statistic.
A minimum compression ratio of 1.91:1 shall be achieved with the Canterbury corpus and 1.63:1
with the Calgary corpus, when the data is transferred through the turboIP-G2 using FTP.
The turboIP-G2 shall never produce a compression ratio less than 1 with any data, that is, the size
of the compressed flows shall always be less than or equal to the size that the flow would have
been if compression were disabled for that flow.
1.3 Software Update
The turboIP-G2 is factory-shipped with the latest version of operating software. If a software
update is needed, it can be downloaded from Comtech EF Data’s Web site
(
www.comtechefdata.com ) or obtained from Comtech EF Data Customer Support during normal
business hours via e-mail or on CD by standard mail delivery.
The turboIP-G2 Software Update process is as follows: