Subject: www.rfc-editor.org and www.ietf.org TCP window scaling

From: Mikael Abrahamsson <[email-masked]>
Date: Wed, 20 Mar 2013 14:04:18 +0100 (CET)

Hello.

As far as I can tell, www.rfc-editor.org doesn't support TCP window 
scaling. It also doesn't support ftp on its IPv6 address:

swmike@uplift:~$ telnet -4 www.rfc-editor.org 21
Trying 64.170.98.47...
Connected to rfc-editor.org.
Escape character is '^]'.
220 "FTP Server Ready"
quit
221 Goodbye.
Connection closed by foreign host.
swmike@uplift:~$ telnet -6 www.rfc-editor.org 21
Trying 2001:1890:126c::1:2f...
telnet: Unable to connect to remote host: Connection refused

14:00:38.045593 IP (tos 0x10, ttl 64, id 33826, offset 0, flags [DF], 
proto TCP (6), length 60) xxx.xxx.xxx.xxx.36300 > 64.170.98.47.21: Flags 
[SEW], cksum 0xc541 (correct), seq 1822128746, win 5840, options [mss 
1460,sackOK,TS val 3080584776 ecr 0,nop,wscale 7], length 0

14:00:38.224653 IP (tos 0x0, ttl 57, id 0, offset 0, flags [DF], proto TCP 
(6), length 56) 64.170.98.41.21 > xxx.xxx.xxx.xxx.36300: Flags [S.], cksum 
0x9c17 (correct), seq 831902177, ack 1822128747, win 5792, options [mss 
1460,sackOK,TS val 332539598 ecr 3080584776], length 0

I get 124 kilobyte/s when I download 
<ftp://ftp.rfc-editor.org/in-notes/tar/RFC-all.tar.gz>. That seems quite 
slow by todays standards. Since I have 179ms delay, it doesn't really hit 
me as indicating 16 or 32 kilobyte window size, but somewhere in between.

www.ietf.org doesn't seem to support TCP window scaling either:

13:58:13.565917 IP xxx.xxx.xxx.xxx.41603 > 12.22.58.30.80: Flags [SEW], 
seq 3844537042, win 5840, options [mss 1460,sackOK,TS val 3080548657 ecr 
0,nop,wscale 7], length 0

13:58:13.746501 IP 12.22.58.30.80 > xxx.xxx.xxx.xxx.41603: Flags [S.], seq 
4206253981, ack 3844537043, win 5792, options [mss 1460,sackOK,TS val 
357513706 ecr 3080548657], length 0

Any specific reason for this? My host connects with "wscale 7".

-- 
Mikael Abrahamsson    email: [email-masked]