RWIN for ADSL 3 Mbits / 256 kbps

[gonzalo76]

Hello,

I'm a CableNut user since a very long time and I always have the same doubt about these 4 settings:

DefaultReceiveWindow, DefaultSendWindow, GlobalMaxTcpWindowSize, TcpWindowSize.


OS: Windows XP SP3
Internet conexion: ADSL 3 Mbits / 256 kbps
ISP: Arnet (Telecom)
Country: Argentina
Latency: around 300/350 ms

TCP Analyzer Resulst:

« SpeedGuide.net TCP Analyzer Results »
Tested on: 10.29.2009 23:45
IP address: 190.226.xx.xx
Client OS: Windows XP

TCP options string: 020405ac0103030101010402
MSS: 1452
MTU: 1492
TCP Window: 127776 (multiple of MSS)
RWIN Scaling: 1 bits (2^1=2)
Unscaled RWIN : 63888
Recommended RWINs: 63888, 127776, 255552, 511104, 1022208
BDP limit (200ms): 5111kbps (639KBytes/s)
BDP limit (500ms): 2044kbps (256KBytes/s)
MTU Discovery: ON
TTL: 49
Timestamps: OFF
SACKs: ON
IP ToS: 00000000 (0)

So, here are my questions:

1. Are my actual settings correct ?
DefaultReceiveWindow = 127776
DefaultSendWindow = 32768
GlobalMaxTcpWindowSize = 127776
TcpWindowSize = 127776

2. I read that DefaultReceiveWindow, GlobalMaxTcpWindowSize and TcpWindowSize should have the same value if you use Windows XP. Is this correct ?

3. What is or should be the recommended RWIN value for my conexion ?
63888, 127776, 255552, 511104 or 1022208 ?


Thank you very kindly,
Gonzalo

[j79zlr]

I would try these settings:

DefaultReceiveWindow = 393216
DefaultSendWindow = 32768
DisableAddressSharing = 1
InitialLargeBufferCount = 200
InitialMediumBufferCount = 480
InitialSmallBufferCount = 640
LargeBufferSize = 819200
MaxFastTransmit = 64000
MediumBufferSize = 150400
Priority Boost = 0
SmallBufferSize = 12800
TransmitWorker = 32
FastSendDatagramThreshhold = 4096
EnableFastRouteLookup = 1
EnablePMTUDiscovery = 1
IgnorePushBitsOnReceives = 0
GlobalMaxTcpWindowSize = 40656
MaxFreeTcbs = 8000
MaxHashTableSize = 16384
MaxNormLookupMemory = 5000000
SackOpts = 1
SynAttackProtect = 1
Tcp1323Opts = 0
TcpLogLevel = 1
TcpMaxDupAttacks = 3
TcpMaxHalfOpen = 100
TcpMaxHalfOpenRetired = 80
TcpRecvSegmentSize = 1452
TcpSendSegmentSize = 1452
TcpTimedWaitDelay = 30
TcpUseRFC1122UrgentPointer = 0
TcpWindowSize = 40656
MaxConnectionsPer1_0Server = 20
MaxConnectionsPerServer = 10
DefaultTimeToLive = 64
DefaultUserTOSSetting = 0
TcpMaxDataRetransmissions = 6
DefaultTOSValue = 240

[gonzalo76]

I would try these settings:

DefaultReceiveWindow = 393216
DefaultSendWindow = 32768
GlobalMaxTcpWindowSize = 40656
TcpWindowSize = 40656

Could you please explain me two things ?

1. Why 393216 under DefaultReceiveWindow ?

2. 40656 is lower than 63888 and also is not a recommended value for RWIN.

Many thanks for your help,
Gonzalo

[j79zlr]

The DefaultReceiveWindow is a function of your download speed, 3Mbps = 3072kbps.

The GlobalMaxTcpWindowSize is a function of your download speed and latency and is a multiple of your TcpRecvSegmentSize.