3Com 3CRWE554G72TU | WDS

Archived from groups: (More info?)

On Thu, 22 Sep 2005 22:52:10 -0400, "John Smith"
<jsmith1970@charter.net> wrote:

>My wireless setup, consisting of two 3CRWE554G72TU, routers is as follows:

| http://www.3com.com/products/en_US/detail.jsp?tab=featu...

>Router 1...
>
>IP Address: 192.168.1.1
>SSID: routerU (U for upstairs)
>DHCP server: enabled
>MAC filtering: enabled
>64-bit WEP: enabled
>Firewall: enabled
>WDS: enabled (with wireless mac address of 2)
>Router is connected to Cable modem Motorola SB5120 which gets signal from
>Charter Pipeline.
>
>Router 2...
>
>IP Address: 192.168.1.2
>SSID: routerD (D for downstairs)
>DHCP server: DISABLED
>MAC filtering: enabled
>64-bit WEP: enabled
>Firewall: enabled
>WDS: enabled (with wireless mac address of 1)
>Vonage adapter Linksys PAP2 is connected to this router.
>
>The routers are setup at two corners of my house and this wireless setup is
>working very nicely.
>
>Questions:
>1. the time shown by Router 2 is "Internet time: Thu Jan 1 00:34:43 1970".
>Time shown by Router 1 correct. What do I need to change so that router 2
>has the correct time?

Nice description. I'm not familiar with this model wireless router.
If it has an NTP/SNTP (simple network time protocol) client, then it
needs to be set to point to a timer server. The data sheet at:
| http://www.3com.com/products/en_US/detail.jsp?tab=featu...
shows that SNTP is supported, but I can't tell if it's a server or a
client. I couldn't find anything on the 3com web pile which shows the
specific pages of the config. Look for NTP or SNTP client setup.

If router #1 is getting its time from an NTP server correctly, it
might be possible for router #2 to point the SNTP client to router #1.

>2. router 2 shows the following in hardware status: LAN Port #4 10 Half
>Duplex
>This is for the Linksys PAP2 vonage adapter. Should it be full duplex? Does
>it matter? Do I need to make a change?

Leave it alone. The Linksys PAP2 probably default to 10baseT-HDX
(half duplex). It really doesn't matter for VoIP because the data
rates for voice are so slow compared to the ethernet speeds.
10baseT-HDX should give about 6Mbits/sec thruput. VoIP using G.729
codec needs about 54Kbits/sec. Unless you have over 1500 simultaneous
conversations going, raising the 6Mbits/sec to something faster isn't
going to do anything.

>3. what tools can I use the monitor the traffic between the two units?

Just *BETWEEN* router 1 and router 2? Well, that's a wireless link.
You could sniff the wireless traffic with a passive sniffer such as
Kismet (under Linux). You could capture the wireless traffic with
Ethereal. Unfortunately, both routers do not support SNMP so you can
use any of the standard SNMP traffic monitors (MRTG, RRDTool, etc).
What are you trying to measure? Number of connections? Traffic?
Intrusion detection?

>Thanks in advance.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice Skype: JeffLiebermann
# http://www.LearnByDestroying.com AE6KS
# http://802.11junk.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com

Archived from groups: (More info?)

Jeff, thanks for your response. Please see inline.

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:63s6j1pe3d9qs87ij6fmla6qdg0bhccemh@4ax.com...
> On Thu, 22 Sep 2005 22:52:10 -0400, "John Smith"
> <jsmith1970@charter.net> wrote:

<deleted> my n/w config...see original post </deleted>

>>Questions:
>>1. the time shown by Router 2 is "Internet time: Thu Jan 1 00:34:43
>>1970".
>>Time shown by Router 1 correct. What do I need to change so that router 2
>>has the correct time?
>
> Nice description. I'm not familiar with this model wireless router.
> If it has an NTP/SNTP (simple network time protocol) client, then it
> needs to be set to point to a timer server. The data sheet at:
> |
> http://www.3com.com/products/en_US/detail.jsp?tab=featu...
> shows that SNTP is supported, but I can't tell if it's a server or a
> client. I couldn't find anything on the 3com web pile which shows the
> specific pages of the config. Look for NTP or SNTP client setup.
>
> If router #1 is getting its time from an NTP server correctly, it
> might be possible for router #2 to point the SNTP client to router #1.

The client setup does not have a place where NTP server can be set up.
Router 1 is displaying the correct time. I would assume that Router 2 would
mirror that somehow. I'll poke around the interface some more.


>>2. router 2 shows the following in hardware status: LAN Port #4 10 Half
>>Duplex
>>This is for the Linksys PAP2 vonage adapter. Should it be full duplex?
>>Does
>>it matter? Do I need to make a change?
>
> Leave it alone. The Linksys PAP2 probably default to 10baseT-HDX
> (half duplex). It really doesn't matter for VoIP because the data
> rates for voice are so slow compared to the ethernet speeds.
> 10baseT-HDX should give about 6Mbits/sec thruput. VoIP using G.729
> codec needs about 54Kbits/sec. Unless you have over 1500 simultaneous
> conversations going, raising the 6Mbits/sec to something faster isn't
> going to do anything.

Agreed. Vonage seems to need 90kbps for best connection (at least that's
what the config on their web-site says). I have even used Skype and Gizmo on
a laptop "wirelessly" connected to Router 2. They all work PERFECTLY.

My concern was regarding the network working at the "lowest common multiple"
of the devices connected, which in this case would be 10Mbps (this is pure
speculation...I would be perfectly happy to be wrong on this). I would hate
for that to happen. Hence the question.

>>3. what tools can I use the monitor the traffic between the two units?
>
> Just *BETWEEN* router 1 and router 2? Well, that's a wireless link.
> You could sniff the wireless traffic with a passive sniffer such as
> Kismet (under Linux). You could capture the wireless traffic with
> Ethereal. Unfortunately, both routers do not support SNMP so you can
> use any of the standard SNMP traffic monitors (MRTG, RRDTool, etc).
> What are you trying to measure? Number of connections? Traffic?
> Intrusion detection?

This question came about after I read through your posts (as well as Steve
Berry's) in the thread entitled "Extending a wireless network". I was
interested in knowing the throughput, # of collisions, and any other
parameters which should be measured on a n/w!! Can you recommend? I'll try
the tools you recommend and see what metrics they have to offer.

Thanks again.

Archived from groups: (More info?)

On Fri, 23 Sep 2005 03:17:27 GMT, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:

>If it has an NTP/SNTP (simple network time protocol) client, then it
>needs to be set to point to a timer server.

Oops. That's a time server, not a timer server.
See:
http://www.clock.org
http://ntp.isc.org




--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice Skype: JeffLiebermann
# http://www.LearnByDestroying.com AE6KS
# http://802.11junk.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com

Archived from groups: (More info?)

On Thu, 22 Sep 2005 23:46:06 -0400, "John Smith"
<jsmith1970@charter.net> wrote:

>The client setup does not have a place where NTP server can be set up.
>Router 1 is displaying the correct time. I would assume that Router 2 would
>mirror that somehow. I'll poke around the interface some more.

In that case, the NTP time server is imbedded in the firmware
somewhere. Google is your friend:
| http://www.cabling-design.com/forums/Re-How-to-set-the-...
See page 81 of the manual at:
| http://support.3com.com/infodeli/tools/wireless/3crwe55...
which mumbles somemthing about:
The Router reads the correct time from NTP servers on the Internet
and sets its system clock accordingly. The Daylight Savings option
merely advances the system clock by one hour. It does not cause the
system clock to be updated for daylight savings time automatically.
I can't read the screen shots in the manual for some odd reason. It's
in there somewhere. Perhaps you need to forward port 123 from the
router #1 to the IP address of router #2. I'm not sure this will work
but it's easy enough to try.

>Agreed. Vonage seems to need 90kbps for best connection (at least that's
>what the config on their web-site says). I have even used Skype and Gizmo on
>a laptop "wirelessly" connected to Router 2. They all work PERFECTLY.

Skype uses the more efficient (and better sounding) iLBC codec.
Again, with the huge difference in required versus available
bandwidth, just about any voice codec will work. What would be more
intersting is watching high bandwidth streaming video with a small
read-ahead buffer from a locally attached server. You should see the
effects of store and forward plus interference with that. Connect via
wireless to each router and compare.

>My concern was regarding the network working at the "lowest common multiple"
>of the devices connected, which in this case would be 10Mbps (this is pure
>speculation...I would be perfectly happy to be wrong on this). I would hate
>for that to happen. Hence the question.

I have no idea what you mean by "lowest common multiple".

>This question came about after I read through your posts (as well as Steve
>Berry's) in the thread entitled "Extending a wireless network". I was
>interested in knowing the throughput, # of collisions, and any other
>parameters which should be measured on a n/w!! Can you recommend? I'll try
>the tools you recommend and see what metrics they have to offer.

Well, access to that level of information requires either SNMP support
with a proper MIB file, or command line access to the radio directly,
as is available in the various Linux mutations for the WRT54G. For
example, the "wl" command is what I use:
| http://wrt-wiki.bsr-clan.de/index.php?title=Wl_command
Lots of detail and plenty of options to tweak. However, the 3com
until may not support such low level tweaking and counters.

Thruput, you can measure with a connecting PC using any of the
"bandwidth meter" programs available. I use Netstat Live:
| http://www.analogx.com/contents/download/network/nsl.ht...

It's possible that 3com has some better wireless diagnostic and
optimization tools. Google didn't find any but it might be worth a
call to support or a question in the appropriate newsgroups or weblog.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice Skype: JeffLiebermann
# http://www.LearnByDestroying.com AE6KS
# http://802.11junk.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com

Archived from groups: (More info?)

Jeff, thanks again.

1. forwarding port 123 did not help. I think that this is a bug in their
firmware.
2. using the tool that you recommened (Netstat), I did the following tests.

Machine 1: Dell laptop with Intel PRO/Wireless 2200BG wireless
Machine 2: Dell desktop with D-Link G520 (used D-Link drivers and windows
wireless config)
Router 1: 3COM 3CRWE554G72TU (with DHCP, 64bit WEP, firewall, MAC filtering,
WDS, WAN)
Router 2: 3COM 3CRWE554G72TU (no DHCP, 64bit WEP, firewall, MAC filtering,
WDS)

Activity: copy a 1GB VOB file from Machine 2 to Machine 1

Setup 1:
Machine 1 ---(wired)--- Router1 ---(wireless)--- Machine 2 (all three
in same room)
Setup 2:
Machine 1 ---(wireless)--- Router1 ---(wireless)--- Machine 2 (all
three in same room)
Setup 3:
Machine 1 ---(wireless)--- Router2 ---(wireless)---
Router1 ---(wireless)--- Machine 2 (Machine 1 and Router 2 in one room,
Machine 2 and Router 1 in same room, rooms about 30ft apart)

Monitoring the following - Netstat "Incoming" Current, Average, Max in
Kbps (bits not bytes). I think that average and max are not good metrics in
this case. What might be more useful may be the mode (most frequently seen
speed). The number I am writing below is the modal value.

Setup 1: 25 Mbps (max 26Mbps, low variance)
Setup 2: 9 Mbps (max 11Mbps, very high variance)
Setup 3: 5 Mbps (max 5.5Mbps, medium variance)

I was surprised to see that Setup 1 was as fast as it was. Expecting setup 2
to be faster.

Your thoughts?

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:at47j19e4ea0ic247ag6knjrrbupt2rk7u@4ax.com...
> On Thu, 22 Sep 2005 23:46:06 -0400, "John Smith"
> <jsmith1970@charter.net> wrote:
>
>>The client setup does not have a place where NTP server can be set up.
>>Router 1 is displaying the correct time. I would assume that Router 2
>>would
>>mirror that somehow. I'll poke around the interface some more.
>
> In that case, the NTP time server is imbedded in the firmware
> somewhere. Google is your friend:
> |
> http://www.cabling-design.com/forums/Re-How-to-set-the-...
> See page 81 of the manual at:
> |
> http://support.3com.com/infodeli/tools/wireless/3crwe55...
> which mumbles somemthing about:
> The Router reads the correct time from NTP servers on the Internet
> and sets its system clock accordingly. The Daylight Savings option
> merely advances the system clock by one hour. It does not cause the
> system clock to be updated for daylight savings time automatically.
> I can't read the screen shots in the manual for some odd reason. It's
> in there somewhere. Perhaps you need to forward port 123 from the
> router #1 to the IP address of router #2. I'm not sure this will work
> but it's easy enough to try.
>
>>Agreed. Vonage seems to need 90kbps for best connection (at least that's
>>what the config on their web-site says). I have even used Skype and Gizmo
>>on
>>a laptop "wirelessly" connected to Router 2. They all work PERFECTLY.
>
> Skype uses the more efficient (and better sounding) iLBC codec.
> Again, with the huge difference in required versus available
> bandwidth, just about any voice codec will work. What would be more
> intersting is watching high bandwidth streaming video with a small
> read-ahead buffer from a locally attached server. You should see the
> effects of store and forward plus interference with that. Connect via
> wireless to each router and compare.
>
>>My concern was regarding the network working at the "lowest common
>>multiple"
>>of the devices connected, which in this case would be 10Mbps (this is pure
>>speculation...I would be perfectly happy to be wrong on this). I would
>>hate
>>for that to happen. Hence the question.
>
> I have no idea what you mean by "lowest common multiple".
>
>>This question came about after I read through your posts (as well as Steve
>>Berry's) in the thread entitled "Extending a wireless network". I was
>>interested in knowing the throughput, # of collisions, and any other
>>parameters which should be measured on a n/w!! Can you recommend? I'll try
>>the tools you recommend and see what metrics they have to offer.
>
> Well, access to that level of information requires either SNMP support
> with a proper MIB file, or command line access to the radio directly,
> as is available in the various Linux mutations for the WRT54G. For
> example, the "wl" command is what I use:
> | http://wrt-wiki.bsr-clan.de/index.php?title=Wl_command
> Lots of detail and plenty of options to tweak. However, the 3com
> until may not support such low level tweaking and counters.
>
> Thruput, you can measure with a connecting PC using any of the
> "bandwidth meter" programs available. I use Netstat Live:
> | http://www.analogx.com/contents/download/network/nsl.ht...
>
> It's possible that 3com has some better wireless diagnostic and
> optimization tools. Google didn't find any but it might be worth a
> call to support or a question in the appropriate newsgroups or weblog.

Archived from groups: (More info?)

On Sun, 25 Sep 2005 20:03:54 -0700, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:

>>Setup 2: 9 Mbps (max 11Mbps, very high variance)
>
>That's wireless client to client with no WDS. That should be almost
>exactly half of of the above 25Mbits/sec thruput. The loss is
>probably due to interference between the two wireless clients, which
>cannot legally be operated synchronously and only one transmitter may
>be on at a time. You might wanna try to enable CTS/RTS flow control
>in the 3com router. That will help with some of the collisions. The
>thruput will be somewhat reduced but so will the collisions.

There's another possible reason for the dismal thruput performance.
Most wireless clients treat the presence of other clients as
interference. I find it difficult to maintain a 54Mbit/sec connection
in the same room as other active wireless clients. In this benchmark
arrangement, you are guaranteed to have both wireless clients
simultaneously active, so the these clients may decide that there's
some interference. The usual reaction is to slow down the connection
to improve reliability. That may also explain the slowdown and
erratic speed variations.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558