MTU stuck at 1460? Can you check yours for me?

[mrapoc]

im gonna keep it there coz jeff recommends it - tweaking for max dsl
unless there is a better setting
and yes i am using it

[Jeff]

 Remember to always reboot equipment and PC after altering any changes, empty out your caches so DSL Reports doesn`t confuse any new tests with earlier ones performed

Tweaking is what the name suggests. It will either slightly increase or decrease your performance. Personally, I think we read too much into tweaking, especially these days with Max. I used to tweak my DUN connection as the difference between a throughput of 4KB/sec and 6 KB/sec could often mean days saved waiting for a download to finish!

If I was to set up 2 identical machines on two identical lines, one with  windows default setting and one with tweaked settings, without performing any speedtests, would you be able to tell the difference? Honestly, I wouldn`t ... it`s a bit like the Pentium 4 2.2GHz vs Pentium 4 2.4GHz, only SiSoft and 3D Mark et al will tell you the difference, if you use `em both normally, not even Bill Gates would know the difference

[Thar]

Well bugger me!

Have recently been reading a post on another board where the poster was asking for RWIN advice. I thought I'd check my settings with DSL Reports as I haven't done it for some time.

Guess what...my MTU is now showing as 1478!

Now the only thing I can think of that I have changed since discovering the problem is Zone Alarm. I recently upgraded from 5. something to 6.1.744. I not 100% certain that it's the cause but after updating ZA I noticed my speeds had increased slightly.

My RWIN figure wasn't the same as I have set in DrTCP but I've re-tweaked that and it's now reporting correctly.

If anyone still has this anomalie, try doing a tweak test and see what you get.

Happy now! 

[Rolacka]

Mine seems fine.

Receive Window (RWIN):    128480
Window Scaling:    1
Path MTU Discovery:    ON
RFC1323 Window Scaling:    ON
RFC1323 Time Stamping:    OFF
Selective Acks:    ON
MSS requested:    1460
TTL:    unknown
TTL remaining:    53
TOS/TOS subfield:    0
TOS/Flags:    

2. Test 1024001 byte download      Actual data bytes sent: 1077101
Actual data packets: 740
Max packet sent (MTU): 1500
Max packet recd (MTU): 1500
Retransmitted data packets: 37
sacks you sent: 147
pushed data pkts: 172
data transmit time: 31.934 secs
our max idletime: 1419.6 ms
transfer rate: 31652 bytes/sec
transfer rate: 253 kbits/sec
This is not a speed test!
transfer efficiency: 95%

[equk]

surely MTU will never be 1500 on ADSL PPPoA as the PPP headers take up a certain number of bytes?

Here's some info I found.

For pppoa/vcmux in the UK the optimal MTU is 1478 - the pppoa overhead is
10. (1478+10) / 48 = 31 whole cells, each which get another 5 bytes ATM
header added.

Windows PPPoE connection supports an IP MTU of 1480 bytes. The 20 bytes of overhead consist of the PPPoE header (6 bytes), the largest possible outer PPP header (4 bytes), the largest possible Multilink PPP header (4 bytes), the largest possible PPP header for compression and encryption (4 bytes), and the PPP header that identifies the actual packet being sent (2 bytes).

A size of 1492 is the highest MTU a PPPoE DSL connection can attain. This is because of the extra 8 bytes required for Encapsulating the PPP protocol to Ethernet

I notice a few ISPs suggest changing MTU to 1492 on PPPoA so not sure 

[mrapoc]

honestly, lol, maybe if it was getting you 10KB/s extra but i doubt it will even get you this...id rather have more stability than a small increase in speed (found this out while tweaking my connection!)

[equk]

I just tried that broadbandreports thing:

Actual data bytes sent: 1077281
Actual data packets: 751
Max packet sent (MTU): 1480
Max packet recd (MTU): 1500
Retransmitted data packets: 37
sacks you sent: 152
pushed data pkts: 104
data transmit time: 33.219 secs
our max idletime: 2821.3 ms
transfer rate: 30245 bytes/sec
transfer rate: 241 kbits/sec
This is not a speed test!
transfer efficiency: 95%

[Thar]

honestly, lol, maybe if it was getting you 10KB/s extra but i doubt it will even get you this...id rather have more stability than a small increase in speed (found this out while tweaking my connection!)

It's never been about the speed.  I just couldn't understand why my MTU was stuck at 1460 despite using various tweaking tools and it reporting correctly in the registy.

I'm still not sure what it was but at least it's reporting correctly now. 

[MoHux]

Thar, I think you may have something re' Zone Alarm.  I had the same thing here.
Reading your post I checked mine, and it now reads correctly.
Like you the only thing different is the latest version of the firewall!! 

BTW those getting 95% 'ish, I think your RWins are too low (if you're on MAX), you should up it to around the low 200,000.  Say 201640 to start.  Then try the test again.

HTH

[Thar]

Thanks for backing up my suspicion MoHux.

Now I have that sorted I can experiment with the RWIN...  

[yamster]

I know this is a very old topic but I am on FTTC and have the exact same issue. I have double checked and taken my network kit and computers to another house and the MTU shows correct but at my house the MTU only comes up as 1460.

The issue with the MTU only being 1460 is gaming lag where I am behind other players and also website will not load correctly. I have contacted IDNet support so I am waiting for a response.