Comtech EF Data turboIP-G2 - Manual (Page 33)

turboIP-G2 Performance Enhancement Proxy Revision 2
Introduction CD-TURBOIP-G2
1–11
• Explicit Congestion Notification (ECN). Traditionally, TCP/IP networks signal
congestion by dropping packets. When ECN is successfully negotiated, an ECN-aware
router may set a mark in the IP header instead of dropping a packet in order to signal
impending congestion. The receiver of the packet echoes the congestion indication to the
sender, which must react as though a packet was dropped.
• Rate Pacing. turboIP-G2 meters out bursty traffic at a rate not to exceed the configured
transmission rate of the satellite channel. This prevents the satellite channel from
becoming congested.
• Per-Connection. turboIP-G2 allows Per-Connection Mode to support dynamic
bandwidth paths, where the bandwidth may be different for any of the paths being
accelerated by the turboIP-G2. Treats any loss as an indication of congestion and reduces
the throughput by half
• Error Tolerance. turboIP-G2 allows Error Tolerance Mode to support dynamic
bandwidth paths, where the bandwidth may be different for any of the paths being
accelerated by the turboIP-G2. Will tolerate 1/12 amount of loss in a window before
reducing the throughput to half.
When Rate Pacing Mode, Pre-Connection Mode or Error Tolerance Mode are
selected to optimize TCP acceleration performance:
• Rate Pacing Mode should be used when the bandwidth path for accelerated
TCP traffic remains constant with the set WAN Transmission Rate.
• Per-Connection Mode should be used to support dynamic bandwidth paths,
where the bandwidth may be different for any of the paths being accelerated by
the turboIP-G2 and there is low congestion in networks.
• Error Tolerance Mode should be used to support dynamic bandwidth paths,
where the bandwidth may be different for any of the paths being accelerated by
the turboIP-G2 and there is high congestion in networks.
1.2.4.3 Selective Acceleration
Selective Acceleration implemented by the Comtech turboIP-G2 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-G2. The rules have three parts:
1) An accounting part that specifies the location and status of the rule in the table;
2) A filter part that matches the datagram’s passing through the turboIP-G2 to each rule;
3) 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: