I just tried a Colchester proxy - and it does seem faster on a miss:
D:\temp\wget>wget -S -Yon
http://www.supernews.com/stats/active.txt
--19:40:37--
http://www.supernews.com/stats/active.txt
=> `active.txt.16'
Resolving colc-cache-3.server.ntli.net... 213.107.224.11
Connecting to colc-cache-3.server.ntli.net[213.107.224.11]:8080... connected.
Proxy request sent, awaiting response...
1 HTTP/1.0 200 OK
2 Date: Sat, 02 Apr 2005 18:40:40 GMT
3 Server: Apache/1.3.31 (Unix) DAV/1.0.3 mod_perl/1.29 mod_ssl/2.8.19 OpenSSL/0
.9.7d
4 Last-Modified: Sat, 02 Apr 2005 00:00:27 GMT
5 ETag: "cb9610-160471-424de09b"
6 Accept-Ranges: bytes
7 Content-Length: 1442929
8 Content-Type: text/plain
9 Age: 1
10 Via: HTTP/1.1 ntl_site (Traffic-Server/5.2.4-59306 [cMsSfW])
100%[====================================>] 1,442,929 261.36K/s ETA 00:00
19:40:47 (163.81 KB/s) - `active.txt.16' saved [1442929/1442929]
But this is an Inktomi cache (others were Netapps) - so it might have had its RWIN tweaked higher.
So then I tried a Bromley one (also Inktomi) and it exhibits the same - but even faster!
D:\temp\wget>wget -S -Yon
http://www.supernews.com/stats/active.txt
--19:46:05--
http://www.supernews.com/stats/active.txt
=> `active.txt.20'
Resolving cache2-bmly.server.ntli.net... 80.1.224.5
Connecting to cache2-bmly.server.ntli.net[80.1.224.5]:8080... connected.
Proxy request sent, awaiting response...
1 HTTP/1.0 200 OK
2 Date: Sat, 02 Apr 2005 18:46:07 GMT
3 Server: Apache/1.3.31 (Unix) DAV/1.0.3 mod_perl/1.29 mod_ssl/2.8.19 OpenSSL/0
.9.7d
4 Last-Modified: Sat, 02 Apr 2005 00:00:27 GMT
5 ETag: "cb9610-160471-424de09b"
6 Accept-Ranges: bytes
7 Content-Length: 1442929
8 Content-Type: text/plain
9 Age: 0
10 Via: HTTP/1.1 ntl_site (Traffic-Server/5.2.4-59306 [c sSf ])
100%[====================================>] 1,442,929 316.95K/s ETA 00:00
19:46:12 (265.17 KB/s) - `active.txt.20' saved [1442929/1442929]
So it is looking rather like the Inktomis have had their max RWIN size increased but not the Netapps.