Custom Optimization

   Custom Optimization is mostly suitable for advanced users. You can optimize important connection settings like MTU (Maximum Transmission Unit), RWIN (TCP Receive Window Size) manually by using Custom Optimization. Some of the important parameters you can optimize with Speed Master are:

MTU (Maximum Transmission Unit)

   MTU (Maximum Transmission Unit) is simply maximum size (in bytes) of a packet that can be transferred over network. When your computer makes a connection with your ISP or another computer, they must agree on the MTU to transfer data.

MSS (Maximum Segment Size)

   MSS (Maximum Segment Size) is the largest amount of data that is put in a packet. This value is usually 40 less than MTU.

RcvWindow (TCP Receive Window Size)

   RcvWindow (TCP Receive Window Size) represents the size of the data (in bytes) a sender may transmit without receiving an acknowledgment. Setting this value too small will cause a slower throughput. For better results RWIN should be an even multiple of the TCP MSS.

Max DupAcks

   Fast Retransmission and Fast Recovery of TCP connections are encountering IP packet loss in the network. These mechanisms allow a TCP sender to quickly infer a single packet loss and resend the packet after receiving duplicate acknowledgments for a previously sent and acknowledged TCP/IP packet. This mechanism is useful when the network is intermittently congested and intervening routers or switches are dropping packets.

TTL (Time To Live)

   A field in the IP header which indicates how long this packet should be allowed to survive before being discarded. It is primarily used as a hop count. If the IP packet does not reach to destination after passing specified number of hops, it is dropped. Due to growth of the internet, the recommended value for TTL is 128.

Session Keep Alive

   Specifies how often to send session keepalive packets on active sessions. The minimum is 60 seconds. The default is 3600 seconds.

PMTU Discovery

   Enabling this feature provides TCP to discover the Maximum Transmission Unit (MTU) over the entire path to the remote host. By discovering the maximum possible transmission unit along the path and restricting TCP messages to this size, fragmentation is eliminated until the message reaches the destination. PMTU Discovery is enabled in Windows by default. The only drawback of enabling this parameter is the delay in discovering the MTU size.

BlackHole Detection

   This setting enables "black hole" routers to be detected. "Black hole" routers do not send back ICMP "Datagram Too Big" messages during PMTU Auto Discovery process. In most cases, it is recommended to disable this feature in order to get a better performance.

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