piranha
07-07-01, 08:36 AM
I have a debate with a buddy in a french forum. He affirm that his MTU is 576 for his dial-up connexion. But his best results is with a RWIN of 4087 (????) and TTL at 128. In my opinion, his REAL MTU is not 576 because (see his TCP/IP results below) :
- MTU results = 576 BUT most performant RWIN is 4087 and 4087 is not a multiple of 536 (576-40).
- that seems to be confirm by "maximum useful data in each packet = 524, which is less than MSS because of Timestamps, or other TCP/IP options used". Suspect, isnt it ??
- and by this : "For optimum performance, consider changing RWIN to a multiple of MSS." If dial-up optimum settings is MSS at 536, this comments reveals that his connexion DONT HAVE MSS at 536... What do you think of that ?!
- why his manuel TTL is 128 and the results below shows a "Time to live left = 114 hops" ???
Your comments and conclusion please !!!! In your opinion what is his MTU ???????
His TCP/IP analyser results :
MTU = 576
MTU value seems to be optimized for dial-up. Consider increasing your MTU to 1500 for better throughput.
MSS = 536
Maximum useful data in each packet = 524, which is less than MSS because of Timestamps, or other TCP/IP options used.
MSS is not fully optimized for broadband (although it might work well for slower connections). Consider increasing your MTU value.
Default Receive Window (RWIN) = 4087
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 4087
For optimum performance, consider changing RWIN to a multiple of MSS.
Other values for RWIN that might work well with your current MTU/MSS:
523136 (MSS x 122 * scale factor of 8)
261568 (MSS x 122 * scale factor of 4)
130784 (MSS x 122 * scale factor of 2)
65392 (MSS x 122)
bandwidth * delay product:
Your RcvWindow limits you to: 163.48 kbps (20.435 KBytes/s) @ 200ms
Your RcvWindow limits you to: 65.392 kbps (8.174 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.
MTU Discovery (RFC1191) = OFF
Time to live left = 114 hops
TTL value is ok.
Timestamps (RFC1323) = ON
Note: Timestamps add 12 bytes to the TCP header of each packet, reducing the space available for useful data.
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349)= 00000000
Thanks.
- MTU results = 576 BUT most performant RWIN is 4087 and 4087 is not a multiple of 536 (576-40).
- that seems to be confirm by "maximum useful data in each packet = 524, which is less than MSS because of Timestamps, or other TCP/IP options used". Suspect, isnt it ??
- and by this : "For optimum performance, consider changing RWIN to a multiple of MSS." If dial-up optimum settings is MSS at 536, this comments reveals that his connexion DONT HAVE MSS at 536... What do you think of that ?!
- why his manuel TTL is 128 and the results below shows a "Time to live left = 114 hops" ???
Your comments and conclusion please !!!! In your opinion what is his MTU ???????
His TCP/IP analyser results :
MTU = 576
MTU value seems to be optimized for dial-up. Consider increasing your MTU to 1500 for better throughput.
MSS = 536
Maximum useful data in each packet = 524, which is less than MSS because of Timestamps, or other TCP/IP options used.
MSS is not fully optimized for broadband (although it might work well for slower connections). Consider increasing your MTU value.
Default Receive Window (RWIN) = 4087
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 4087
For optimum performance, consider changing RWIN to a multiple of MSS.
Other values for RWIN that might work well with your current MTU/MSS:
523136 (MSS x 122 * scale factor of 8)
261568 (MSS x 122 * scale factor of 4)
130784 (MSS x 122 * scale factor of 2)
65392 (MSS x 122)
bandwidth * delay product:
Your RcvWindow limits you to: 163.48 kbps (20.435 KBytes/s) @ 200ms
Your RcvWindow limits you to: 65.392 kbps (8.174 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.
MTU Discovery (RFC1191) = OFF
Time to live left = 114 hops
TTL value is ok.
Timestamps (RFC1323) = ON
Note: Timestamps add 12 bytes to the TCP header of each packet, reducing the space available for useful data.
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349)= 00000000
Thanks.