MTU value won't change among other things.

Shagster · Post by **Shagster** » Sun Oct 26, 2003 12:52 pm

Right now it has been 2 weeks since our retarded IT department has gotten me and everyone else anything better than 56k speeds over the 3 t3 lines they have.

I just need to know two things. First, trying to set an mtu of 1500 will not stick. If I restart the stupid value of 1420 is still there no matter what program I use. Can the campus network force that on every user?

Second, Im not sure of what rcv window to use. There is 2 T3 lines and the rest of the stuff equals exactly that of a third T3 line distributed over about 7,500 campus computers including personal.

I've been trying to use cablenut's MTU fixer and that didn't work so I went to the SGO and that didn't work.

MTU = 1420
MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput.
MSS = 1380
MSS is not fully optimized for broadband (although it might work well for slower connections). Consider increasing your MTU value.

Default Receive Window (RWIN) = 64240
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 64240

For optimum performance, consider changing RWIN to a multiple of MSS.
Other values for RWIN that might work well with your current MTU/MSS:
507840 (MSS x 46 * scale factor of 8)
253920 (MSS x 46 * scale factor of 4)
126960 (MSS x 46 * scale factor of 2)
63480 (MSS x 46)
bandwidth * delay product:

Your RcvWindow limits you to: 2569.6 kbps (321.2 KBytes/s) @ 200ms
Your RcvWindow limits you to: 1027.84 kbps (128.48 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = OFF
Time to live left = 50 hops

TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 01011100

Precedence (priority) = 100 (flash override)
Delay = 1 (low delay)
Throughput = 1 (high throughput)
Reliability = 0 (normal reliability)
Cost = 1 (low cost)

I'd appreciate any help. Thankyou.

mccoffee · Post by **mccoffee** » Sun Oct 26, 2003 12:56 pm

Are you running any virtual private network software on those computers???

Yeah they can force that on every user if the routers are using 1420

Shagster · Post by **Shagster** » Sun Oct 26, 2003 1:21 pm

I haven't been using any VPN. I guess the router is forcing 1420. Do you know of any reasons they would have for setting that?

mccoffee · Post by **mccoffee** » Sun Oct 26, 2003 2:04 pm

vpn is my theory.

mnosteele52 · Post by **mnosteele52** » Sun Oct 26, 2003 2:55 pm

Hey Shaggy try searching your registry for the value 1420 just to make sure it's not something on your pc. Aslo have a friend do a TCP/IP Analyzer test and see what his MTU reports as, that way you can narrow down the problem. Once you set it right, at 1500, we can optimize everything else.

Andrzej · Post by **Andrzej** » Sun Oct 26, 2003 3:00 pm

school server (also routers) can limited MTU=1420 internet connection
in both services:
ICS = internet connection sharing
VPN = virtual private network
mentioned campus network MTU=1420 limitation
can be changed ONLY in MTU settings in server (router) by IT people

BTW some MTU limitations (means additional encapsulation)
are from sq reason (customer identification)

you can INFORM yours OS about mentioned limitation in two ways:
- install access manager prg (if not essential - not recomended)
+ OS registry setting modyfication manualy or prg + last one recomended

on SG TCP/IP Analyzer result MTU=1420 for eg laptop one can see:
--laptop wOS default MTU (not present by default means value MTU=1500 for plain TCP/IP)

++laptop MTU value equal 1420 registry setting & plain TCP/IP - strongly recomended
--laptop MTU value more than limited - NOT recomended
with MTU registry settings above limitted value you can see same problems
eg unable reach same www; fragmentation lanMTU & slow down your speed

OTOH for shure laptop registry value MTU one can see on SG Analyzer
if OS registry setting will be less than limitted MTUvalue
in this case less than MTU=1420
+ can be try for confirmation of registry inscription

IMVHO if realy needed ... check exact laptop settings
compare both:
1. actual mentioned campus network SG TCP/IP Analyzer result
2. diferent connection - laptop directly connection to modem

PS re: rwin value
should be from acctual MSS value (1380)
acording to acctual MAL & dwl results
:2cool: see mnosteele52 PLEASEread
http://forums.speedguide.net/showthread ... did=113043 MAL

Shagster · Post by **Shagster** » Sun Oct 26, 2003 3:05 pm

Originally posted by mccoffee
vpn is my theory.

Do you mean that I'm setup as a vpn or that the campus is or what?

Shagster · Post by **Shagster** » Sun Oct 26, 2003 4:04 pm

Originally posted by Andrzej
school server (also routers) can limited MTU=1420 internet connection
in both services:
ICS = internet connection sharing
VPN = virtual private network
mentioned campus network MTU=1420 limitation
can be changed ONLY in MTU settings in server (router) by IT people

BTW some MTU limitations (means additional encapsulation)
are from sq reason (customer identification)

you can INFORM yours OS about mentioned limitation in two ways:
- install access manager prg (if not essential - not recomended)
+ OS registry setting modyfication manualy or prg + last one recomended

on SG TCP/IP Analyzer result MTU=1420 for eg laptop one can see:
--laptop wOS default MTU (not present by default means value MTU=1500 for plain TCP/IP)
++laptop MTU value equal 1420 registry setting & plain TCP/IP - strongly recomended
--laptop MTU value more than limited - NOT recomended
with MTU registry settings above limitted value you can see same problems
eg unable reach same www; fragmentation lanMTU & slow down your speed

OTOH for shure laptop registry value MTU one can see on SG Analyzer
if OS registry setting will be less than limitted MTUvalue
in this case less than MTU=1420
+ can be try for confirmation of registry inscription

IMVHO if realy needed ... check exact laptop settings
compare both:
1. actual mentioned campus network SG TCP/IP Analyzer result
2. diferent connection - laptop directly connection to modem

PS re: rwin value
should be from acctual MSS value (1380)
acording to acctual MAL & dwl results
:2cool: see mnosteele52 PLEASEread
http://forums.speedguide.net/showthread ... did=113043 MAL

The registry verifies my computer is set as MTU=1500. I can't get an optimized rcv window yet since I don't know what the best mss value is as well as what to enter for my internet capable bandwidth. I guess the normal since the fall semester started is 5.5Mbs down and 5.5Mbs up. But what about mss?

mnosteele52 · Post by **mnosteele52** » Sun Oct 26, 2003 4:10 pm

Have you checked another pc on the college network to verify that it is the college limiting your MTU?

Shagster · Post by **Shagster** » Sun Oct 26, 2003 4:23 pm

Originally posted by mnosteele52
Have you checked another pc on the college network to verify that it is the college limiting your MTU?

Ok, I just checked my roomate computer and a friends down the hall. I reconfigured the registry to be an MTU of 1500. restarted and double checked the registry and it was still set. then I checked the SGanalyser and still indicating 1420.

mnosteele52 · Post by **mnosteele52** » Sun Oct 26, 2003 4:34 pm

If they are all 1420 then it's the university that is limiting it and there is nothing you can do. I would ask your IT department what the deal is and why are they doing this (this can save them money since it lowers your overall bandwidth). For the time being I would suggest using the following settings in CableNut:

DefaultReceiveWindow = 768000
DefaultSendWindow = 768000
DisableAddressSharing = 1
InitialLargeBufferCount = 200
InitialMediumBufferCount = 480
InitialSmallBufferCount = 640
LargeBufferSize = 819200
MaxFastTransmit = 64000
MediumBufferSize = 150400
PriorityBoost = 0
SmallBufferSize = 12800
TransmitWorker = 32
FastSendDatagramThreshold = 4096
EnableFastRouteLookup = 1
EnablePMTUDiscovery = 1
IgnorePushBitsOnReceive = 0
GlobalMaxTcpWindowSize = 60720
MaxFreeTcbs = 8000
MaxHashTableSize = 16384
MaxNormLookupMemory = 5000000
SackOpts = 1
SynAttackProtect = 1
Tcp1323Opts = 0
TcpLogLevel = 1
TcpMaxDupAcks = 3
TcpMaxHalfOpen = 100
TcpMaxHalfRetried = 80
TcpRecvSegmentSize = 1380
TcpSendSegmentSize = 1380
TcpTimedWaitDelay = 30
TcpUseRFC1122UrgentPointer = 0
TcpWindowSize = 60720
MaxConnectionsPer1_0Server = 20
MaxConnectionsPerServer = 10
DefaultTTL = 64
DisableUserTOSSetting = 0
TcpMaxDataRetransmissions = 6
DefaultTOSValue = 240

Shagster · Post by **Shagster** » Sun Oct 26, 2003 4:42 pm

Aright, many thanks. I would find the optimized rcv window but my campus blocks pings and I can't do a tracert. Ill stop by or something because this is rediculous. Paying over $20k a year for this school.

Also, if i'm not mistaken. Cant they give us an mtu of 1500 and just limit the packet size and make everyoen happy?

Andrzej · Post by **Andrzej** » Sun Oct 26, 2003 4:59 pm

with speed 5.5/5.5 MBps MAL is minimal
so not such important for you

Shagster · Post by **Shagster** » Tue Oct 28, 2003 11:57 am

Originally posted by mnosteele52
If they are all 1420 then it's the university that is limiting it and there is nothing you can do. I would ask your IT department what the deal is and why are they doing this (this can save them money since it lowers your overall bandwidth). For the time being I would suggest using the following settings in CableNut:

DefaultReceiveWindow = 768000
DefaultSendWindow = 768000
DisableAddressSharing = 1
InitialLargeBufferCount = 200
InitialMediumBufferCount = 480
InitialSmallBufferCount = 640
LargeBufferSize = 819200
MaxFastTransmit = 64000
MediumBufferSize = 150400
PriorityBoost = 0
SmallBufferSize = 12800
TransmitWorker = 32
FastSendDatagramThreshold = 4096
EnableFastRouteLookup = 1
EnablePMTUDiscovery = 1
IgnorePushBitsOnReceive = 0
GlobalMaxTcpWindowSize = 60720
MaxFreeTcbs = 8000
MaxHashTableSize = 16384
MaxNormLookupMemory = 5000000
SackOpts = 1
SynAttackProtect = 1
Tcp1323Opts = 0
TcpLogLevel = 1
TcpMaxDupAcks = 3
TcpMaxHalfOpen = 100
TcpMaxHalfRetried = 80
TcpRecvSegmentSize = 1380
TcpSendSegmentSize = 1380
TcpTimedWaitDelay = 30
TcpUseRFC1122UrgentPointer = 0
TcpWindowSize = 60720
MaxConnectionsPer1_0Server = 20
MaxConnectionsPerServer = 10
DefaultTTL = 64
DisableUserTOSSetting = 0
TcpMaxDataRetransmissions = 6
DefaultTOSValue = 240

Alrighty, sorry for the late reply but I was waiting for a slow time to test out those settings. It is really hard to know if theirs a difference because the tests still show sporadic results. However I will keep them since I totally trust what you say to be fact

Thanks again for your help.

Andrzej · Post by **Andrzej** » Tue Oct 28, 2003 3:15 pm

would you kind explain your acctual results:
SG TCP/IP Analyzer
dwl speed test

Shagster · Post by **Shagster** » Tue Oct 28, 2003 5:07 pm

Originally posted by Andrzej
would you kind explain your acctual results:
SG TCP/IP Analyzer
dwl speed test

It is irrelevent to post anything since the tests are too sporadic to mean anything.

Shagster · Post by **Shagster** » Thu Oct 30, 2003 1:27 pm

Called IT and they didn't know what an MTU value was and they said rcv window doesn't effect anything. Instead of saying anything I hung up.

A little off topic but what college department would you go to to get a refund for random services (such as falsified high speed internet

)

mnosteele52 · Post by **mnosteele52** » Thu Oct 30, 2003 1:38 pm

Well that's par for the course for an IT dept. Most IT people are morons if you ask me. Our IT guy for the Fire Department is a moron, our network is so unsecure and the way the whole system is setup is backwards ass.

Shagster · Post by **Shagster** » Thu Oct 30, 2003 2:08 pm

Originally posted by mnosteele52
Well that's par for the course for an IT dept. Most IT people are morons if you ask me. Our IT guy for the Fire Department is a moron, our network is so unsecure and the way the whole system is setup is backwards ass.

I hear you, I worked for my colleges hardware department and quit since I didn't like having a boss that knew less than me

The speeds over the summer were 13 up and 13 down. At my work place they were 20 up and 20 down. Now the **** hit the fan.

j79zlr · Post by **j79zlr** » Thu Oct 30, 2003 8:02 pm

college networks are highly congested, little you can do. You get those high speeds in the summer because they aren't using the bandwith.

Shagster · Post by **Shagster** » Thu Oct 30, 2003 8:44 pm

Originally posted by j79zlr
college networks are highly congested, little you can do. You get those high speeds in the summer because they aren't using the bandwith.

Yeah I know, but they are doing a horrible job organizing it.

Andrzej · Post by **Andrzej** » Fri Oct 31, 2003 12:22 pm

Shaggy : ... I didn't like having a boss that knew less than me ...
who like them ?
but IMVHO the most important is to be more pragmatic
than answers to questions: like & disslike sth or sb