Overview
This article describes what happens if a packet is lost between Exinda devices when performing packet aggregation, in an environment with traffic acceleration enabled.
Information
- With optimization/acceleration, the TCP connection between the client and server is broken up into three:
- There is one TCP connection between the client and the client-side Exinda.
- One between the two Exindas.
- One from the server-side Exinda to the server.
If a packet is lost between the two Exindas, it is retransmitted by the sending Exinda, as per normal TCP (either due to duplicate ACKs or a timeout).
SNACK is a mechanism to stop retransmitting packets that have been successfully received at the other end. For example, if they have four packets, the second of which is lost, SNACK will stop packets 3 and 4 from being retransmitted, since they arrived correctly.
The other method is to use SACK instead. It fulfills the same role in the opposite direction. SNACK tells the other end which packets have not been received, whereas SACK tells the other end which packets have been received.
Priyanka Bhotika
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