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Standard User glossywhite
(newbie) Tue 07-Feb-12 22:29:22
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Orange Bright Box: Set the MTU value to anything you like!


[link to this post]
 
Here is how you bypass the restriction to disallow MTU values higher than 1492, that Orange placed on the "Bright Box":

http://www.youtube.com/watch?v=yKmbDiyh4_8
Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 01:43:18
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
As a matter of interest, in the BB Settings section I presume you manually blanked out the BB Password?

Cuz one of my quibbles with the BrightBox is that it shows all passwords in clear, thereby making it awkward to demonstrate my other settings to someone else without giving the game away.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 08:30:38
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
But can you be sure that you have allowed the router to operate with MTU > 1492 everywhere? All you have shown is that the user can input such values and that they are stored, but how do you know that the router does not restrict the MTU elsewhere in its operation, like packaging packets?

You showed earlier that the code contains 11 tests for MTU > 1492 spread over 3 files. I would expect that the field input and storage of the MTU value, which you address here, would require no more than 2 tests. So what are the other 9 tests restricting?

The only way to prove that you have successfully allowed that you can have MTU > 1492 is:
  1. With MTU at its default "max" of 1492, run ping -f -l 1472 bbc.co.uk. It should fail with "Packet needs to be fragmented but DF set."
  2. With MTU = 1500 (which is the max it can be, in case you don't know) by your method, again run ping -f -l 1472 bbc.co.uk. It should no longer fail.
FYI: The number in the ping is required MTU-28.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC


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Standard User glossywhite
(newbie) Wed 08-Feb-12 13:57:39
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: XRaySpeX] [link to this post]
 
In reply to a post by XRaySpeX:
But can you be sure that you have allowed the router to operate with MTU > 1492 everywhere? All you have shown is that the user can input such values and that they are stored, but how do you know that the router does not restrict the MTU elsewhere in its operation, like packaging packets?

You showed earlier that the code contains 11 tests for MTU > 1492 spread over 3 files. I would expect that the field input and storage of the MTU value, which you address here, would require no more than 2 tests. So what are the other 9 tests restricting?

The only way to prove that you have successfully allowed that you can have MTU > 1492 is:
  1. With MTU at its default "max" of 1492, run ping -f -l 1472 bbc.co.uk. It should fail with "Packet needs to be fragmented but DF set."
  2. With MTU = 1500 (which is the max it can be, in case you don't know) by your method, again run ping -f -l 1472 bbc.co.uk. It should no longer fail.
FYI: The number in the ping is required MTU-28.


Hey, I only showed you how to hack the values. Here's a question: why don't you try it? I've done so, and after changing to "1500", all pings timed out (using Windows CMD... I'm an Ubuntu guy).

However, I went to http://www.speedguide.net:8080 and it correctly reports my MTU as 1500 when I set it to 1500, and 1492 when I set it to 1492.

Edited by glossywhite (Wed 08-Feb-12 14:09:47)

Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 14:31:56
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
I've no interest in switching browsers just for a minor experiment; easier for me to switch routers!
In reply to a post by glossywhite:
after changing to "1500", all pings timed out
They shouldn't! Then I guess you've proved your mod doesn't work. I trust you were able to translate my Windows pings to your OS.

wink I thought this was a collaboration. I provided the Theory of the MTU, which you didn't appear to know, and you provided your hardware hacking expertise.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 14:42:11
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
In reply to a post by glossywhite:
after changing to "1500", all pings timed out (using Windows CMD... I'm an Ubuntu guy).
Ah, I see! On Linux ping -D -s 1472 bbc.co.uk should run OK!

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User glossywhite
(newbie) Wed 08-Feb-12 15:06:35
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: XRaySpeX] [link to this post]
 
In reply to a post by XRaySpeX:
In reply to a post by glossywhite:
after changing to "1500", all pings timed out (using Windows CMD... I'm an Ubuntu guy).
Ah, I see! On Linux ping -D -s 1472 bbc.co.uk should run OK!


You guys want to change the MTU, not me. I simply showed you how to alter the HTTP post info, to change the setting. If you want something modifying in the free software/open-source world, the source is there, and you are free to do it yourself. Am I to sit here all day, working out why an MTU setting is incorrect? *I* don't care, nor do I want to change mine. You guys do, and I provided as much as I know how, thus far, to get you started.

How about I let you try it yourself, and test it at: http://www.speedguide.net:8080/



SG TCP/IP Analyzer

IP Address: 95.148.XXXXXXX (95.148.XXXXXXX)
Client OS: Linux
Browser: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:10.0) Gecko/20100101 Firefox/10.0
Please Read the Analyzer FAQ if the above is not your IP address.
TCP options string = 020405b40402080a0019424f0000000001030307
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1448, which is less than MSS because of Timestamps, or other TCP/IP options used.
Default TCP Receive Window (RWIN) = 14720
RWIN Scaling (RFC1323) = 7 bits (scale factor: 2^7=128)
Unscaled TCP Receive Window = 115

Under many Linux distributions, the Analyzer only shows the Current TCP Window. FAQ
RWIN seems to be set to a very small number. If you're on a broadband connection, consider using a larger value.
For optimum performance, consider changing RWIN to a multiple of MSS.
Other RWIN values that might work well with your current MTU/MSS:
64240 (up to 2 Mbit lines, depending on latency. MSS * 44)
128480 (1-5 Mbit lines, depending on latency. MSS * 44 * 2)
256960 (2-14 Mbit lines, depending on latency. MSS * 44 * 2^2)
513920 (8-30 Mbit lines, depending on latency. MSS * 44 * 2^3)
1027840 (25-60 Mbit lines depending on latency. MSS * 44 * 2^4)
bandwidth * delay product (Note this is not a speed test):

Your TCP Window limits you to: 589 kbps (74 KBytes/s) @ 200ms
Your TCP Window limits you to: 236 kbps (29 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.
MTU Discovery (RFC1191) = ON
Time to live left = 47 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 (0)


Let me ask this: Why would Orange lock the Bright Box MTU to 1492, were it meant to go higher?

Edited by glossywhite (Wed 08-Feb-12 15:14:45)

Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 16:21:47
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
It was you who claimed that you had cracked the restriction that MTU cannot be > 1492, both in OP of this thread and in other thread. No one asked you to; you did it out of your interest in such matters and more power to your elbow.

It is not sufficient to just be able to input and store such values, they need to take effect in all subsequent operations, particularly in view of the numerous IF MTU > 1492 tests in the code. It is also not sufficient to code something without testing it thoroughly.

All I was asking you for is to show the results of that simple ping in the 2 circumstances I outlined. This is the accepted way of measuring MTUs; see http://www.kitz.co.uk/adsl/MTU2.htm

There is no need to rely on an involved webpage. For all we know it is just making some TCP/IP request for the target system to return its MTU setting rather than measuring it explicitly.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User glossywhite
(newbie) Wed 08-Feb-12 16:59:31
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: XRaySpeX] [link to this post]
 
I seek to remove this post, as it turns out that the method used is not working... yet.


I shall update the thread, once the proper method has been tested and confirmed. How does this thread become removed? There is no report option... a weird forum layout.

Edited by glossywhite (Wed 08-Feb-12 17:12:57)

Standard User XRaySpeX
(eat-sleep-adslguide) Wed 08-Feb-12 18:14:41
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Re: Orange Bright Box: Set the MTU value to anything you lik


[re: glossywhite] [link to this post]
 
In reply to a post by glossywhite:
How does this thread become removed?
It can't! Just because it may be technically incorrect, it does not break any forum rules. Posts may be edited and deleted by the author for up to 12 hours but that has elapsed. Sufficient that you posted a retraction here.

NP. I'm glad we are now able to agree and hope we can work together in future to get on top of this smile

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
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