Re: 8159 bytes takes 20 ms, 8160 bytes takes 200 ms?

From: Alexander Nickolov (agnickolov_at_mvps.org)
Date: 10/13/04 

Date: Wed, 13 Oct 2004 10:19:20 -0700

Actually, that would be delayed ACK, since there's no data in
the ACK packet. 

-- 
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================
"Arkady Frenkel" <arkadyf@hotmailxdotxcom> wrote in message 
news:e6dpK2PsEHA.3076@TK2MSFTNGP09.phx.gbl...
> Nagle always with us :) , look for Nagle algorithm in TCP
> Arkady
>
> "Itjalve" <itjalve@hotmail.com.(donotspam)> wrote in message
> news:2E997F61-BFFA-49E0-B0DE-5876E692943C@microsoft.com...
>> Win2k communicating with an embedded system via a point-to-point link
> using
>> tcp winsock. 8159 bytes (7 fragments) takes about 20 milli seconds, 8160
>> bytes (8 fragments) takes about 200 milli seconds.
>>
>> Its looks like that win2k waits about 150 ms before ack the last, 8,
>> fragment. Is this a win2k problem or is it my application that is slow?
>>
>> I have checked my code for delays, but I can't find any problems there,
> i'm
>> waiting for packets and the cpu load is less than 10%.
>>
>> //
>> this is what etheral shows, a packet with ack and push flag set, and 
>> win2k
>> (192.168.125.2) waits 0.15s before sending the ack
>> //
>>
>> No.     Time        Source                Destination           Protocol
> Info
>>   47727 36.458361   192.168.125.1         192.168.125.2         TCP
>> 5515 > 2179 [PSH, ACK] Seq=2400562144 Ack=2286139454 Win=8192 Len=304
>>
>> Frame 47727 (358 bytes on wire, 358 bytes captured)
>>     Arrival Time: Oct 13, 2004 08:13:02.001731000
>>     Time delta from previous packet: 0.000535000 seconds
>>     Time since reference or first frame: 36.458361000 seconds
>>     Frame Number: 47727
>>     Packet Length: 358 bytes
>>     Capture Length: 358 bytes
>> Ethernet II, Src: 00:00:23:08:80:33, Dst: 00:04:76:22:89:fe
>>     Destination: 00:04:76:22:89:fe (00:04:76:22:89:fe)
>>     Source: 00:00:23:08:80:33 (00:00:23:08:80:33)
>>     Type: IP (0x0800)
>> Internet Protocol, Src Addr: 192.168.125.1 (192.168.125.1), Dst Addr:
>> 192.168.125.2 (192.168.125.2)
>>     Version: 4
>>     Header length: 20 bytes
>>     Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
>>         0000 00.. = Differentiated Services Codepoint: Default (0x00)
>>         .... ..0. = ECN-Capable Transport (ECT): 0
>>         .... ...0 = ECN-CE: 0
>>     Total Length: 344
>>     Identification: 0x2384 (9092)
>>     Flags: 0x04 (Don't Fragment)
>>         0... = Reserved bit: Not set
>>         .1.. = Don't fragment: Set
>>         ..0. = More fragments: Not set
>>     Fragment offset: 0
>>     Time to live: 64
>>     Protocol: TCP (0x06)
>>     Header checksum: 0x9ac7 (correct)
>>     Source: 192.168.125.1 (192.168.125.1)
>>     Destination: 192.168.125.2 (192.168.125.2)
>> Transmission Control Protocol, Src Port: 5515 (5515), Dst Port: 2179
> (2179),
>> Seq: 2400562144, Ack: 2286139454, Len: 304
>>     Source port: 5515 (5515)
>>     Destination port: 2179 (2179)
>>     Sequence number: 2400562144
>>     Next sequence number: 2400562448
>>     Acknowledgement number: 2286139454
>>     Header length: 20 bytes
>>     Flags: 0x0018 (PSH, ACK)
>>         0... .... = Congestion Window Reduced (CWR): Not set
>>         .0.. .... = ECN-Echo: Not set
>>         ..0. .... = Urgent: Not set
>>         ...1 .... = Acknowledgment: Set
>>         .... 1... = Push: Set
>>         .... .0.. = Reset: Not set
>>         .... ..0. = Syn: Not set
>>         .... ...0 = Fin: Not set
>>     Window size: 8192
>>     Checksum: 0x91d9 (correct)
>> Data (304 bytes)
>>
>>
>> No.     Time        Source                Destination           Protocol
> Info
>>   47728 36.609320   192.168.125.2         192.168.125.1         TCP
>> 2179 > 5515 [ACK] Seq=2286139454 Ack=2400562448 Win=17216 [CHECKSUM
>> INCORRECT] Len=0
>>
>> Frame 47728 (54 bytes on wire, 54 bytes captured)
>>     Arrival Time: Oct 13, 2004 08:13:02.152690000
>>     Time delta from previous packet: 0.150959000 seconds
>>     Time since reference or first frame: 36.609320000 seconds
>>     Frame Number: 47728
>>     Packet Length: 54 bytes
>>     Capture Length: 54 bytes
>> Ethernet II, Src: 00:04:76:22:89:fe, Dst: 00:00:23:08:80:33
>>     Destination: 00:00:23:08:80:33 (00:00:23:08:80:33)
>>     Source: 00:04:76:22:89:fe (00:04:76:22:89:fe)
>>     Type: IP (0x0800)
>> Internet Protocol, Src Addr: 192.168.125.2 (192.168.125.2), Dst Addr:
>> 192.168.125.1 (192.168.125.1)
>>     Version: 4
>>     Header length: 20 bytes
>>     Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
>>         0000 00.. = Differentiated Services Codepoint: Default (0x00)
>>         .... ..0. = ECN-Capable Transport (ECT): 0
>>         .... ...0 = ECN-CE: 0
>>     Total Length: 40
>>     Identification: 0xf909 (63753)
>>     Flags: 0x04 (Don't Fragment)
>>         0... = Reserved bit: Not set
>>         .1.. = Don't fragment: Set
>>         ..0. = More fragments: Not set
>>     Fragment offset: 0
>>     Time to live: 128
>>     Protocol: TCP (0x06)
>>     Header checksum: 0x0000 (incorrect, should be 0x8671)
>>     Source: 192.168.125.2 (192.168.125.2)
>>     Destination: 192.168.125.1 (192.168.125.1)
>> Transmission Control Protocol, Src Port: 2179 (2179), Dst Port: 5515
> (5515),
>> Seq: 2286139454, Ack: 2400562448, Len: 0
>>     Source port: 2179 (2179)
>>     Destination port: 5515 (5515)
>>     Sequence number: 2286139454
>>     Acknowledgement number: 2400562448
>>     Header length: 20 bytes
>>     Flags: 0x0010 (ACK)
>>         0... .... = Congestion Window Reduced (CWR): Not set
>>         .0.. .... = ECN-Echo: Not set
>>         ..0. .... = Urgent: Not set
>>         ...1 .... = Acknowledgment: Set
>>         .... 0... = Push: Not set
>>         .... .0.. = Reset: Not set
>>         .... ..0. = Syn: Not set
>>         .... ...0 = Fin: Not set
>>     Window size: 17216
>>     Checksum: 0x7b6f (incorrect, should be 0x5689)
>>
>>
>>
>>
>>
>>
>>
>>
>
>

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