@anush3070 wrote:
I have enabled the jumbo frames, i.e set MTU as 9192.
Still no effect.
I have -
workstations --> switch --> SRX300 --> modem(PPPoE) --> FTTC cabinet --> Internet
I have to adjust MTU differently on all these different types of device as more encapsulation occurs at each stage, and each type of device has different capabilities as far as maximum MTU is concerned.
Critically, I had to discover if my Fibre cabinet (and its Exchange connection) had been upgraded to accept BJF (yes, it had to full Jumbo frames), then I had to check the maximum MTU the modem could handle, then the maximum that PPPoE would pass through, and so on back to the switch and workstation.
SO the MTU increases as packets pass from workstation to the internet, matching the increase in packet size. Simply adjusting the size on one device in isolation is not sufficient.
I use
admin@MartyMcFly#set security flow tcp-mss all-tcp mss 1350
as a starting point.
When you have it right you know because web pages "snap" rather than dawdle. But it all depends on the specific equipment and how the internet provider has configured your connection, and the ability of the modem to work with different frame sizes. So it would be misleading for me to give you my sizes, because they are not universally applicable. If one device is a bottleneck all the devices connecting to it have to be adjusted.
A lot of people have blogged about this.
Ensure MTU settings in router & PC (if you ever changed it) are 1500.
ping with
ping -f -l nnnn bbc.co.uk
Find largest nnnn for which it doesn't need fragmentation.
Then add 28 to get MTU.
Vigor 130 is RFC 4638 compliant (Baby Jumbo Frames) MTU = 1508
BT uses (VLAN) tag 101
therefore, PC Ethernet interface is set to 1500
My result 1464 + 28 = 1492 (Workstation IPv4 Ethernet MTU is 1500) where are the missing 8 bytes? PPPoE encapsulation.
Assume MTU is 1508, then 1464 + 8 + 28 = 1504 (??4 bytes for VLAN tag??)
Calculation
MTU = PPPoEWrapper + MSSOverhead + MSS
1508 = 4 + 40 + 1464