Winsock MTU values
- For the best performance of Trumpet winsock,
please set the MTU, MSS and RWIN values accordingly:
| Parameter | Value |
|---|---|
| MTU | 576 |
| MSS | 536 |
| RWIN (if you do not have a 16550 UART) | 1608 |
| RWIN (if you do have a 16550 UART) | 4288 |
- The formulas used to calculate these numbers
are as follows:
- MSS = MTU - 40
- RWIN = MSS * 3 for systems without a 16550 UART
- RWIN = MSS * 8 for systems with a 16550 UART
| Term | Definition |
|---|---|
| MTU | Maximum Transfer Unit
The maximum number of bytes that can be sent in a single packet |
| MSS | Maximum Segment Size
The maximum number of user data bytes that can be included in the packet without fragmentation. This is 40 less than the MTU because the IP header occupies these 40 bytes. |
| RWIN | Receive WINdow
The maximum number of bytes that can be received before an acknowledgement is required. By setting a very large RWIN, performance is increased because one acknowledgement packet can acknowledge multiple received packets, however if one packet is in error (i.e. data overrun) then the entire RWIN block must be restransmitted, thus degrading performance. |
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| Last Updated: 2002-08-16 |
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