 boondoggleCogni, Ergo Sum
join:2001-03-26
Caledonia, MI | RWIN, MTU, MSS in NIC vs RT314? Okay -- I've mostly been lurking out here since I got my cable connection & RT314. MUCH help & great advice from many of the regulars here. Thanks!
My connection quality & line speeds are great for the most part, but I'm still trying to twist a little more out -- being a technical type by day  , and I remain a little confused of some of the tweak settings. First, here's my latest tweak test:
»monitor.dslreports.com/tweak/blo···a=normal
This is a cable connection (@home) through their 3com tailfin modem into my RT314, and then on to a 3com NIC in the computer for what it's worth. I've set the RWIN in the NIC to 32k using DrTCP, and let everything else default. [Also, I've got DrTCP's filters in place in addition to the defaults, so I'm not pingable.] Apparently, that gets me an MTU of 1500, and an MSS of 1460. What I don't quite understand is when I list the autoexec.net in the RT314, the canned command is ip tcp mss 512. See below. Where does the MSS 1460 come from if it's set to 512 in the router?
RT314-> sys view autoexec.net
sys errctl 0
sys trcl level 5
sys trcl type 1180
sys trcp cr 96 128
sys trcl sw on
ip tcp mss 512
ip tcp limit 2
ip tcp irtt 65000
ip tcp window 2
ip tcp ceiling 6000
ip rip activate
ip rip merge on
ip icmp disc enif0 off
ppp ipcp com off
sys mbuf debug off
sys wdog sw on
RT314->
--
Si Quaeris Geek Amoenam Circumspice |
|
 SentinelPremium
join:2001-02-07
Florida
kudos:1 | As far as I know you set the Rwin & MTU on the workstation PC and the MTU & RWIN on the router you don't touch unless you are PPPoE. If you are cable you don't adjust the settings in the router. Leave the MTU as Auto on the PC's and set your RWIN. That should be it.
--
~AL~ |
|
 bbarreraPremium,MVM
join:2000-10-23
Sacramento, CA
kudos:1
 ·SureWest Internet
| Speed up FTP firmware updates boonie, your MSS=1460 and RWIN are set in PC's TCP/IP stack and are configured using DrTCP program (on tweak section of this website) or manually editing registry.
The router has it's own TCP/IP stack, and is only used when connecting to the router's internal servers (HTTP, FTP, Telnet). I changed router's TCP MSS and Window after reading a post a couple of months ago (from DrTCP I think). The reason? To speed up FTP firmware updates -- with these tweaks uploading the firmware via FTP should only take ~2 seconds. The default MSS (512) and TCP Receive Window (2xMSS) slow the firmware upload process. I don't notice any speed difference with telnet or web interface.
To change "Router to Internet MSS" you must issue the command "ip adj wanif0 1452." This specific tweak is used for PPPoE, because router's default for PPPoE is MSS=1400 and MTU=1440. It expires after PPPoE session is dropped, and there is a new command in latest Zyxel firmware to make it persistant (ip adjmss 1452).
I don't recommend this, but if you want to tweak MTU for Ethernet/cable modem just replace wanif0 with enif1. For Ethernet encapsulation you can check interfaces with command "ip ifconfig" or "ip ifconfig enif0" or "ip ifconfig enif1."
Checkout this great FAQ on tweaking:
»Tweaking FAQ |
|
AOTMA
join:2001-04-13
Florissant, MO | I'm using my RT311 with PPPoE, and when I type ip ifconfig I get the following:
enif0: mtu 1500
wanif0: mtu 1492
Does this mean my MSS is not the default 1400? |
|
|
|
 DrTCPYours trulyPremium,ExMod 1999-04
join:1999-11-09
Round Rock, TX | You guys are confusing a lot of settings. The first post confused the MSS/Window settings for the internal TCP stack for telnet/ftp/web connections to the router itself with PC settings. These settings are not used when communicating with remote sites.
You found the interface MTU settings alright but additionally there is a separate TCP MSS limit of 1400 despite MTU of interface is 1492 (maximum MSS is 1452). Note that this for TCP connections only and when using PPPoE.
It works like this: If the MSS option in TCP connection establishment packets is greater than the limit set router modifies it down to 1400. Router does it to both SYN and SYN-ACK packets so both sides think the other side has a lower MSS and adjusts its send packet size accordingly. In other words, router is fooling both ends to achieve smaller packet size. UDP or ICMP does not carry MSS in header so they are not bound by this operation.
You can adjust MSS limit via:
ip adj wanif0 1452
This command is only effective after PPPoE connected.
Upcoming firmware has "ip adjmss 1452" command which sets the default MSS and it can be added to autoexec.net to make it permanent. |
|
boondoggleCogni, Ergo Sum
join:2001-03-26
Caledonia, MI
| reply to boondoggle
Re: RWIN, MTU, MSS in NIC vs RT314? Eureka! I'm getting it. I was clearly not snapped-in to how the setting in the router played versus the PC NIC. Also, since I'm not PPPoE, much of the discussion does not apply.
I'm getting more dangerous all the time. Thanks, DrTCP for clarifying my confusion points. 
[looking at the fact that I ended up replying to myself -- I guess I still need work on posting. Back to the books...]
[text was edited by author 2001-04-28 06:44:16] |
|
| reply to DrTCP
Re: Speed up FTP firmware updates I wrote GearMinder, and want to upgrade the software to enter the
MSS limit adjustment automatically every time it renews the WAN.
How can I tell that the command was entered properly? In other
words, what config screens do I view to verify the command?
Thank you.
Dr. Edward Cheung - Author of GearMinder
»www.edcheung.com |
|
bbarreraPremium,MVM
join:2000-10-23
Sacramento, CA
kudos:1 Reviews:
·SureWest Internet
| Here is a menu 24.8 session, typing "ip adj wanif0" will tell you current MSS on WAN:
314>
314> ip adj wanif0
adjust TCP mss on wanif0 to 1400
314>
314> ip adj wanif0 1452
adjust TCP mss on wanif0 to 1452
314>
314> ip adj wanif0
adjust TCP mss on wanif0 to 1452
314> |
|
| Thank you!
»www.edcheung.com |
|
