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marctronixx

join:2003-09-08
Los Angeles, CA

MTU of 1300...

all,

so i did the ping test on this site and came up with 1272 as the lowest before fragmented packets. so i put in the MTU of 1300 (adding the 28 bits for header).

i had no issues with the line (22/6 comcast) but was curious to do the tweak.

i have a linksys e4200 and had its MTU set to auto. now i have it set to MANUAL and 1300 since 1272 is the lowest packet size (1273 was the start of the DF messages in the cmd window).

so i know my packets are probably more since i am reducing the packets over time, but should i use the 1300 MTU of just go back to auto and/or 1500?

i just did a speed test thru the laptop here wireless n and got 81.93 and 7.88 and ping of 5. last night with the "auto" setting (before i did this tweak/ping/dr tcp test) i had 77.61 down and 7.07 up, 6ms ping. i used the comcast speed test link.

would appreciate any feedback. keep at 1300 which is lowest packet size b4 fragmenting, or set it back to auto?

thank you.


Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
kudos:3

• What OS are you running?

• A Cable connection uses 1500 as the MTU.

• A DSL connection uses 1492 as the MTU.

• The box and the router has the same MTU.
--
"You can observe a lot by watching". Yogi Berra


marctronixx

join:2003-09-08
Los Angeles, CA

Irish, you answered my question, or rather you confirmed it.

I'M using old school xp.

If you are still around to answer, why even do this speed test on cable users of the MTU should be 1500. Just some clarification...



Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
kudos:3

I do not have the foggiest why to do the ping test here in the US with a cable connection. Some DSL connections and some providers may use different MTU's. So if your provider does not tell you what to set the MTU to, then the ping test can be useful.

In the Tweaks Forum, the FAQ gives you the "normal" settings for the MTU. However, the ISP may not follow these "normal" settings.


(TCP, IP, MTU and MSS magic numbers)

1500 The biggest-sized IP packet that can normally traverse the Internet without getting fragmented.
Typical MTU for non-PPPoE, non-VPN connections.

1492 The maximum MTU recommended for Internet PPPoE implementations.

1472 The maximum ping data payload before fragmentation errors are received on non-PPPoE, non-VPN connections.

1460 TCP Data size (MSS) when MTU is 1500 and not using PPPoE.

1464 The maximum ping data payload before fragmentation errors are received when using a PPPoE-connected machine.

1452 TCP Data size (MSS) when MTU is 1492 and using PPPoE.

576 Typically recommended as the MTU for dial-up type applications, leaving 536 bytes of TCP data.

48 The sum of IP, TCP and PPPoE headers.

40 The sum of IP and TCP headers.

28 The sum of IP and ICMP headers.



--
"You can observe a lot by watching". Yogi Berra


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