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change mss for PPPoE and IP Route users

Posted: Sun Nov 21, 2021 8:31 am
by network99
hello guys
good time

I calculated my network MTU size from ping 4.2.2.4 -l 1455 -f and I realized my network MTU is 1455

now, I have a question aboute change mss for my users
what ch-mss size should I set for PPPoE-client users and IP Route Users ?

IP Route : 1455-40 = 1415 is correct ?
PPPoE : 1455-40-6 = 1409 is correct ?

Re: change mss for PPPoE and IP Route users

Posted: Sun Nov 21, 2021 10:38 am
by network99
my network :
Image

Re: change mss for PPPoE and IP Route users

Posted: Sun Nov 21, 2021 5:41 pm
by network99
I should set ch-mss on interface (all ppp (my user ppooe)) or set ch-mss on interface connected to internet ??

Re: change mss for PPPoE and IP Route users

Posted: Sun Nov 21, 2021 6:08 pm
by Zacharias
MSS = MTU - TCP Header - IP Header ...
What are those 6 Bytes on your second calculation ?

Re: change mss for PPPoE and IP Route users

Posted: Sun Nov 21, 2021 7:21 pm
by tdw
I calculated my network MTU size from ping 4.2.2.4 -l 1455 -f and I realized my network MTU is 1455
Some ping programs the length option specifies just the payload data, others the entire packet.

For Windows it is the payload, so from that if -l 1455 works and -l 1456 fails the MTU is 20 (IP header) + 8 (ICMP header) + 1455 (payload) = 1483, and correspoding MSS is 1483 (MTU) - 20 (IP header) - 20 (TCP header) = 1443.

Re: change mss for PPPoE and IP Route users

Posted: Thu Nov 25, 2021 10:10 am
by network99
What are those 6 Bytes on your second calculation ?
PPPoE overhead = 8 Byte / its incorrect and not should calculated ?

Re: change mss for PPPoE and IP Route users

Posted: Thu Nov 25, 2021 10:15 am
by network99
I calculated my network MTU size from ping 4.2.2.4 -l 1455 -f and I realized my network MTU is 1455
Some ping programs the length option specifies just the payload data, others the entire packet.

For Windows it is the payload, so from that if -l 1455 works and -l 1456 fails the MTU is 20 (IP header) + 8 (ICMP header) + 1455 (payload) = 1483, and correspoding MSS is 1483 (MTU) - 20 (IP header) - 20 (TCP header) = 1443.
thanks

Re: change mss for PPPoE and IP Route users

Posted: Fri Nov 26, 2021 8:40 pm
by Zacharias
What are those 6 Bytes on your second calculation ?
PPPoE overhead = 8 Byte / its incorrect and not should calculated ?
It is 8 Bytes not 6... yes it should be calculated ...