Date: Wed, 6 Jun 2012 14:35:11 -0700 (PDT) From: alan bryan <alan.bryan@yahoo.com> To: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Slow transfers at higher latencies with high BW - RFC 1323 related? Message-ID: <1339018511.22423.YahooMailNeo@web130101.mail.mud.yahoo.com>
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(also posted to FreeBSD forums) I think I may be having an issue with window scaling (RFC 1323) and am hoping that someone can enlighten me on what's going on. Server: FreeBSD 9, apache22, serving a static 100MB zip file. 192.168.18.30 Client: Mac OS X 10.6, Firefox 192.168.17.47 Network: Only a switch between them - the subnet is 192.168.16/22 Questions: #1: Does this look normal? #2: Is packet #2 specifying a window size of 65535 and a scale of 512? #3: Is packet #5 then shrinking the window size so it can use the 512 scale and still keep the overall calculated window size near 64K? #4: Why is the scale so high? Here's the first 6 packets from wireshark. For packets 5 & 6 I've included the details showing the window size and scaling factor being used for the data transfer. No. Time Source Destination Protocol Length Info 108 6.699922 192.168.17.47 192.168.18.30 TCP 78 49190 > http [SYN] Seq=0 Win=65535 Len=0 MSS=1460 WS=8 TSval=945617489 TSecr=0 SACK_PERM=1 115 6.781971 192.168.18.30 192.168.17.47 TCP 74 http > 49190 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=512 SACK_PERM=1 TSval=2617517338 TSecr=945617489 116 6.782218 192.168.17.47 192.168.18.30 TCP 66 49190 > http [ACK] Seq=1 Ack=1 Win=524280 Len=0 TSval=945617490 TSecr=2617517338 117 6.782220 192.168.17.47 192.168.18.30 HTTP 490 GET /utils/speedtest/large.file.zip HTTP/1.1 118 6.867070 192.168.18.30 192.168.17.47 TCP 375 [TCP segment of a reassembled PDU] Details: Transmission Control Protocol, Src Port: http (80), Dst Port: 49190 (49190), Seq: 1, Ack: 425, Len: 309 Source port: http (80) Destination port: 49190 (49190) [Stream index: 4] Sequence number: 1 (relative sequence number) [Next sequence number: 310 (relative sequence number)] Acknowledgement number: 425 (relative ack number) Header length: 32 bytes Flags: 0x018 (PSH, ACK) Window size value: 130 [Calculated window size: 66560] [Window size scaling factor: 512] Checksum: 0xd182 [validation disabled] Options: (12 bytes) No-Operation (NOP) No-Operation (NOP) Timestamps: TSval 2617517423, TSecr 945617490 [SEQ/ACK analysis] TCP segment data (309 bytes) 119 6.867131 192.168.18.30 192.168.17.47 TCP 1514 [TCP segment of a reassembled PDU] Details: Transmission Control Protocol, Src Port: http (80), Dst Port: 49190 (49190), Seq: 310, Ack: 425, Len: 1448 Source port: http (80) Destination port: 49190 (49190) [Stream index: 4] Sequence number: 310 (relative sequence number) [Next sequence number: 1758 (relative sequence number)] Acknowledgement number: 425 (relative ack number) Header length: 32 bytes Flags: 0x010 (ACK) Window size value: 130 [Calculated window size: 66560] [Window size scaling factor: 512] Checksum: 0xe5cf [validation disabled] Options: (12 bytes) No-Operation (NOP) No-Operation (NOP) Timestamps: TSval 2617517423, TSecr 945617490 [SEQ/ACK analysis] TCP segment data (1448 bytes)
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