The bulk of most network traffic is TCP IPv4 traffic, which SteelHeads typically optimize using a TCP proxy architecture. TCP proxy mode optimization separates a TCP connection into three individual connections:

The advantage of TCP proxy mode is that it increases performance, because the SteelHead acts a local proxy to the host. This enables the SteelHead to perform transport streamlining and application streamlining, which results in increased user performance.

However, sometimes you might want to use the SteelHead optimization to reduce the amount of traffic traversing the WAN. Packet mode optimization provides a simple approach in which the SteelHead looks at a packet, or small group of packets, and performs SDR and LZ on the data payload for data reduction. The host and SteelHead do not create an individual TCP handshake, and the SteelHead reduces payload for packets as the traffic flows through.

The advantage of packet mode optimization is that it is a universal method that applies data streamlining to diverse protocols. The disadvantage is the lack of performance benefits from transport streamlining or application streamlining, because the SteelHead does not proxy or perform intelligent application prediction.

Packet mode optimization is unidirectional—from sender to receiver—which is an effect of not acting as a proxy. For example, take two sites with SteelHeads, Site A and Site B. A device at Site A sends SNMP traps over UDP to a server at Site B, and only SteelHead A is configured to optimize UDP traffic to SteelHead B. If the server at Site B, for some reason, responds over UDP to the device at Site A, this traffic is not optimized unless you have configured SteelHead B to optimize UDP traffic to SteelHead A.