Re: [PLUG] Experience with Verizon FIOS & wireless installation

[JP Vossen <jp@jpsdomain.org>]

> Date: Sun, 30 Sep 2007 11:42:20 -0700
> From: george@georgesbasement.com
> Subject: [PLUG] Experience with Verizon FIOS & wireless installation

<snip>

> The Smoothwall cuts the download speed in half, but the upload speed
> is about the max. for my account (5Mbps down/2Mbps up).  I downloaded
> about 200 MB of upgrades to the two debian PC's behind the Smoothwall
> with Aptitude in about fifteen minutes (250kBps).  That's six times the
> maximum I was getting with DSL.

I got 15/2 FiOS last summer and it's been good, though I don't want to 
say much more for fear of jinxing myself <g>.  I gave the installers a 
sacrificial W2K box and let them do whatever made them happy, and when 
we tested speeds on that, we got pretty close to 15/2.  But I get 
nowhere near that on an unmodified box because TCP stack settings need 
to be tweaked.

They have a little app to do this on Windows, but nothing for Linux. 
Here are the Windows Registry settings I derived by using that app on a 
test box.

Working for me on W2KSP2+ and XP2+ but *not tested* on Vista:

----- Windows cut here -----
REGEDIT4

# Changes made by the Verizon FiOS Optimizer on a test W2K server

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]

# CHANGED
# ========
# WAS: "TcpWindowSize"=dword:0000faf0
# (0004b270 = 307824)
"TcpWindowSize"=dword:0004b270

# NEW
# ========
# 
http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/regentry/58760.mspx
# (0004b270 = 307824)  AKA DefaultRcvWindow
"GlobalMaxTcpWindowSize"=dword:0004b270

# 
http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/regentry/58797.mspx
# SACK is specified in RFC 2018, TCP Selective Acknowledgment Options
# Default is on
"SackOpts"=dword:00000001

# 
http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/regentry/58800.mspx
# RFC 1323, TCP Extensions for High Performance
# Value		Meaning
# 0 (00)	Timestamps and window scaling are disabled.
# 1 (01)	Window scaling is enabled.
# 2 (10)	Timestamps are enabled.
# 3 (11)	Timestamps and window scaling are enabled. [Default]
"Tcp1323Opts"=dword:00000003
----- Windows cut here -----


And here are the appropriate Linux settings, derived from the above and 
from the URL noted in the comment below.  The location (and possibly 
names?) for these may vary by distribution; I don't know enough to say 
for sure.

AFAIK these work for me for Debian, Ubuntu and Red Hat:

----- Linux (Debian/Ubuntu/Red Hat) cut here -----
# FiOS Settings
# /etc/sysctl.conf
# Adapted from http://www.wildblue.cc/wbforums/archive/index.php/t-1415.html
# Do selective acknowledgment
net.ipv4.tcp_sack = 1
# Don't use timestamping
net.ipv4.tcp_timestamps = 0
# Do TCP window scaling
net.ipv4.tcp_window_scaling = 1
# Disables automatic defragmentation (needed for masquerading, LVS)
#net.ipv4.ip_always_defrag = 1
# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
# recommended to increase this for 1000 BT or higher
net.core.netdev_max_backlog = 2500
# Increase Linux TCP buffer limits
net.core.rmem_default = 307824
net.core.rmem_max = 307824
net.core.wmem_max = 8388608
----- Linux (Debian/Ubuntu) cut here -----


If anyone has anything to add to these, I'd be interested to hear!  I'm 
especially interested to know if these settings might impact LAN speeds 
in any way.


Finally, I will also note that during "normal" GUI browsing (99.9% 
Firefox), I haven't noticed a significant difference from Comcast.  But 
during downloads of large files, from decent servers, during non-busy 
times, it flies.  I also tend to download anything large using 'wget' on 
a Debian box because it feels faster to me (copy & paste link from GUI 
browser or whatever), so YMMV.

Hope this is useful,
JP
----------------------------|:::======|-------------------------------
JP Vossen, CISSP            |:::======|        jp{at}jpsdomain{dot}org
My Account, My Opinions     |=========|      http://www.jpsdomain.org/
----------------------------|=========|-------------------------------
Microsoft has single-handedly nullified Moore's Law.
Innate design flaws of Windows make a personal firewall, anti-virus
and anti-malware software mandatory. The resulting software arms race
has effectively flattened Moore's Law on hardware running Windows.
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