How to Implement Compression in SSL

V42.bis Data Compression in SSL V3.0

Note: To understand this document you need a thorough knowledge of the SSL V3.0 protocol. For more about SSL3, see SSL3 draft number "draft302".

At initialization of SSL V3 the client sends the command "Client hello". The "Client hello" includes a list of compression algorithms supported by the client, ordered according to the client's preference. There are no compression algorithms specified in the SSL3 except the ID 0, which means no compression. The compression ID defined by HOB for V42.bis is Hexa "F4".  Therefore, if the client wants to have V42.bis compression, it will send "F4" as compression ID in the "client hello" command. If the server accepts the V42.bis ID it will send the same ID back in the "Server Hello" command and all data will be compressed. Otherwise, the session will be disconnected.
V42.bis needs two parameters N1 and N2. These parameters are set to N1 = 12 and N2 = 250.

webmaster@hobsoft.com, Last Updated: 03-Jul-07