Subject: Bad implementation of TCP fast retransmit by Microsoft ?

From: Ragon Philippe <[email-masked]>
Date: Sun, 30 Apr 2000 17:47:52 +0200

Being involved in the development of a radio network, I had to study the 
trace of an HTTP session that performed very badly in order to assess 
whether it was due to the radio part of the network. I am attaching the 
trace captured on the server, because I would like to have the opinion of 
experts on this list to confirm / infirm my conclusions.

Context :
The client (Internet Explorer) is running on a Windows 95 laptop connected 
to a radio mobile phone.
The server (Internet Information Server 4) is running on a Windows NT 4 SP6 
desktop on an Ethernet LAN.
A tunneling protocol is used between intermediate nodes physically 
connected by an Ethernet network ==> MTU is set to 1450 on the client 
discounting for the tunnel overhead, in order to avoid fragmentation and 
re-assembly at tunnel end-points ==> the client proposes an MSS of 1410
The radio link introduces an important latency that results in a measured 
RTT of 9s for a full-size downlink (server to client) packet that is well 
over the initial RTO of 3s of TCP implementation of Microsoft. In order to 
study the downloading of a large image without being annoyed by this 
discrepancy between the assumed RTT and the real one, a persistent HTTP 
connection is opened to request a short page first (frame 1 to 14) to train 
TCP. Like that, when the request for the large image is issued (frame 15) 
the RTO for the TCP connection  is 12s i.e. above the real RTT (9s).
Frame numbers appearing in the text below refer to numbers in the attached 
trace.

Question / Problem 1 :
The ACK for frame 19 has been lost by the network. Therefore, the content 
of frame 19 is repeated 12s later in frame 23. Then ACK for frame 21 
arrives (of course also acknowledging frame 19)
The server reacts by sending a packet in sequence with what has been ACKed, 
(i.e. SN = end of frame 21 + 1) instead of in sequence with the last packet 
sent (i.e. SN = end of frame 22 + 1),  hence  repeating this packet. Is 
this correct, considering that packet in frame 22 was not (for some reason) 
a full-size one ?
Remark : from this point the RTO is around 24 s

Question / Problem 2 :
Frame 32 is a repetition of frame 26 after 7s. Because RTO at that moment 
is close to 24s we have either :

a buggy early re-transmission but it should not be the case because this 
known Windows problem is supposed to be corrected in SP6 for NT 4 that is 
in use for the server

or :

a buggy fast retransmit. There are two reasons for which I am saying buggy :
- fast retransmit has been triggered by a second duplicate ACK instead of a 
third as mandated by RFC 2581. A confirmation of this lack of compliancy on 
the part of Microsoft appears again with frame 43 which repeats frame 37 
after the reception of a second duplicate ACK
- the second duplicate ACK is not a duplicate ACK. The ACK sequence we have 
is ACK 48714, ACK 48714 and ACK 48855.
I am right on this point ?

Question / Problem 3 :
After frame 26 has been repeated by frame 32, the ACK for frame 26 arrives 
(on time). This triggers the repetition of frames 28 and 30 with frames 34 
and 35 instead of continuing in sequence with the last packet sent (frame 
30). Said otherwise, I would expect the sending of a packet starting with 
SN 53085 instead of 50265 for frame 34

Conclusion :
A single lost ACK  triggers a cascade of unnecessary repetitions that are 
due to :
- a bad implementation of fast retransmit,
- the left side of the window that does not progress as it should.
The problem is self-sustaining as demonstrated by the end of the trace (not 
provided in the file attached which has been cut to a reasonable size) due 
the following pattern :
- early fast retransmit triggers undue repetitions
- undue repetitions trigger early fast retransmit
Between undue repetitions, the left side of the window progress a little 
bit, thanks to what the transfer of the image reaches its end, but only 
after a very looong time.

Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
1       42.845  TCP       ....S., len:   24, seq:   3467580-3467603, ack:         0, win: 8192 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0x9E04; Proto = TCP; Len: 64
+ TCP: ....S., len:   24, seq:   3467580-3467603, ack:         0, win: 8192, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
2       42.846  TCP       .A..S., len:    4, seq:     41191-41194, ack:   3467581, win: 8460,  Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA115; Proto = TCP; Len: 44
+ TCP: .A..S., len:    4, seq:     41191-41194, ack:   3467581, win: 8460, src:   80  dst: 1041 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
3       45.726  TCP       ....S., len:   24, seq:   3467580-3467603, ack:         0, win: 8192 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA004; Proto = TCP; Len: 64
+ TCP: ....S., len:   24, seq:   3467580-3467603, ack:         0, win: 8192, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
4       45.726  TCP       .A...., len:    0, seq:     41192-41192, ack:   3467581, win: 8460,  Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA215; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:     41192-41192, ack:   3467581, win: 8460, src:   80  dst: 1041 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
5       45.804  TCP       .A..S., len:    4, seq:     41191-41194, ack:   3467581, win: 8460,  Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA315; Proto = TCP; Len: 44
+ TCP: .A..S., len:    4, seq:     41191-41194, ack:   3467581, win: 8460, src:   80  dst: 1041 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
6       50.503  TCP       .A...., len:    0, seq:   3467581-3467581, ack:     41192, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA104; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3467581-3467581, ack:     41192, win: 8460, src: 1041  dst:   80 

page 1


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
7       50.858  HTTP      GET Request (from client using port 1041)                            47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA204; Proto = TCP; Len: 302
+ TCP: .AP..., len:  262, seq:   3467581-3467842, ack:     41192, win: 8460, src: 1041  dst:   80 
+ HTTP: GET Request (from client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
8       50.860  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA415; Proto = TCP; Len: 653
+ TCP: .AP..., len:  613, seq:     41192-41804, ack:   3467843, win: 8198, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
9       50.868  TCP       .A...., len:    0, seq:   3467843-3467843, ack:     41192, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA404; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3467843-3467843, ack:     41192, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
10      56.559  HTTP      GET Request (from client using port 1041)                            47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA504; Proto = TCP; Len: 302
+ TCP: .AP..., len:  262, seq:   3467581-3467842, ack:     41192, win: 8460, src: 1041  dst:   80 
+ HTTP: GET Request (from client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
11      56.559  TCP       .A...., len:    0, seq:     41805-41805, ack:   3467843, win: 8198,  Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA515; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:     41805-41805, ack:   3467843, win: 8198, src:   80  dst: 1041 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
12      56.822  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

page 2


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA615; Proto = TCP; Len: 653
+ TCP: .AP..., len:  613, seq:     41192-41804, ack:   3467843, win: 8198, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
13      59.145  TCP       .A...., len:    0, seq:   3467843-3467843, ack:     41805, win: 7847 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA604; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3467843-3467843, ack:     41805, win: 7847, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
14      65.865  TCP       .A...., len:    0, seq:   3467843-3467843, ack:     41805, win: 7847 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA704; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3467843-3467843, ack:     41805, win: 7847, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
15      76.743  HTTP      GET Request (from client using port 1041)                            47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA804; Proto = TCP; Len: 312
+ TCP: .AP..., len:  272, seq:   3467843-3468114, ack:     41805, win: 7847, src: 1041  dst:   80 
+ HTTP: GET Request (from client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
16      76.744  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA715; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     41805-43214, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
17      76.744  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA815; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     43215-44624, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

page 3


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
18      82.187  TCP       .A...., len:    0, seq:   3468115-3468115, ack:     43215, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAA04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     43215, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
19      82.187  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xA915; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     44625-46034, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
20      86.028  TCP       .A...., len:    0, seq:   3468115-3468115, ack:     44625, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAC04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     44625, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
21      86.028  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAA15; Proto = TCP; Len: 1450
+ TCP: .AP..., len: 1410, seq:     46035-47444, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
22      90.976  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAB15; Proto = TCP; Len: 1309
+ TCP: .A...., len: 1269, seq:     47445-48713, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
23      94.381  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

page 4


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAC15; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     44625-46034, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
24      95.629  TCP       .A...., len:    0, seq:   3468115-3468115, ack:     47445, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB104; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     47445, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
25      95.629  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAD15; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     47445-48854, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
26      95.629  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAE15; Proto = TCP; Len: 1450
+ TCP: .AP..., len: 1410, seq:     48855-50264, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
27      97.549  TCP       .A...., len:    0, seq:   3468115-3468115, ack:     48714, win: 7191 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB204; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     48714, win: 7191, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
28      97.549  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xAF15; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     50265-51674, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

page 5


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
29      99.470  TCP       .A...., len:    0, seq:   3468115-3468115, ack:     48714, win: 7191 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB404; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     48714, win: 7191, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
30      99.470  HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB015; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     51675-53084, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
31      102.350 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     48855, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB504; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     48855, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
32      102.394 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB115; Proto = TCP; Len: 1450
+ TCP: .AP..., len: 1410, seq:     48855-50264, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
33      104.750 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     50265, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB804; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     50265, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
34      104.750 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties

page 6


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB215; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     50265-51674, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
35      104.750 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB315; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     51675-53084, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
36      107.150 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     51675, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB904; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     51675, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
37      107.150 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB415; Proto = TCP; Len: 1450
+ TCP: .AP..., len: 1410, seq:     53085-54494, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
38      109.551 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xBB04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
39      109.551 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB515; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     54495-55904, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

page 7


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
40      110.991 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xBD04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
41      110.991 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB615; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     55905-57314, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
42      113.391 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xBE04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
43      113.391 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB715; Proto = TCP; Len: 1301
+ TCP: .AP..., len: 1261, seq:     53085-54345, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
44      115.792 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xBF04; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     53085, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
45      115.792 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol

page 8


Network Monitor trace  Sun 04/30/00 14:44:55  27-04_TCP_Server_3.TXT

+ IP: ID = 0xB815; Proto = TCP; Len: 1167
+ TCP: .AP..., len: 1127, seq:     57315-58441, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
46      118.192 TCP       .A...., len:    0, seq:   3468115-3468115, ack:     54495, win: 8460 47.217.248.130  Srv Guillemot   IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xC104; Proto = TCP; Len: 40
+ TCP: .A...., len:    0, seq:   3468115-3468115, ack:     54495, win: 8460, src: 1041  dst:   80 

*********************************************************************************************************************************
Frame   Time    Protocol  Description                                                          Src Other Addr  Dst Other Addr  Type Other Addr
47      118.219 HTTP      Response (to client using port 1041)                                 Srv Guillemot   47.217.248.130  IP

+ FRAME: Base frame properties
+ ETHERNET: ETYPE = 0x0800 : Protocol = IP:  DOD Internet Protocol
+ IP: ID = 0xB915; Proto = TCP; Len: 1450
+ TCP: .A...., len: 1410, seq:     54495-55904, ack:   3468115, win: 7926, src:   80  dst: 1041 
+ HTTP: Response (to client using port 1041)

page 9


---------------------------------------------------------------------
Philippe Ragon / Tour Atlas / 10, villa d'Este/ 75013 Paris/ FRANCE
Telephone & Fax : (33) 01 45 70 79 53
E-mail                   :   [email-masked]
---------------------------------------------------------------------