Internet connection

[klem kedidelhopper]

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45? I now this is not common practice
but if only one computer is using the line at any particular time
would this work? There will never be a time that two computers will
ever be operating on this line at the same time although for that week
in question they both may be plugged into it though. would this be an
issue? I can arrange to have the new location unplugged during this
time if need be. Thanks for any advice. Lenny

 

On Sun, 30 Sep 2012 16:44:16 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45? I now this is not common practice
but if only one computer is using the line at any particular time
would this work? There will never be a time that two computers will
ever be operating on this line at the same time although for that week
in question they both may be plugged into it though. would this be an
issue? I can arrange to have the new location unplugged during this
time if need be. Thanks for any advice. Lenny

Many desktop computers gave a "wake on LAN" feature in their network
card, co that type computer would always be online.

There is a device that can spli a single RJ45 into two lines. You
might want to check into that. ry cyberguys.com as a source.

 

[mike]

On 9/30/2012 4:44 PM, klem kedidelhopper wrote:

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45?
yes, but only one can be plugged in and it will be a nightmare

for the next guy who tries to figger out why it doesn't work like it
should. Put a plug on the extension wire so you can have only one
connected.

Stick an ethernet switch at the location and you can have as many
plugged in as you have ports on the switch.
They're $10 on ebay, free at garage sales.
If you walk outside in a populated area and yell, "I need an
ethernet swtich," people will come out of the woodwork glad to
get rid of them.
You only have to have the switch powered for a week.


I now this is not common practice

but if only one computer is using the line at any particular time
would this work? There will never be a time that two computers will
ever be operating on this line at the same time although for that week
in question they both may be plugged into it though. would this be an
issue? I can arrange to have the new location unplugged during this
time if need be. Thanks for any advice. Lenny

 

[Jeff Liebermann]

On Sun, 30 Sep 2012 16:44:16 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45?

Yes. It's just an exension cable.

I know this is not common practice
but if only one computer is using the line at any particular time
would this work?

Yes, it will work with only one computah connected.

There will never be a time that two computers will
ever be operating on this line at the same time although for that week
in question they both may be plugged into it though. would this be an
issue?

Yes, it's an issue. Twisted pair ethernet is *NOT* a bus arrangement
as in POTS phone lines. It's a star. Just add a cheap 5 port
ethernet switch where everything comes together and you'll be fine.

I can arrange to have the new location unplugged during this
time if need be. Thanks for any advice. Lenny

No need with an ethernet switch.

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

 

[captainvideo462002@yahoo.]

On Sunday, September 30, 2012 7:44:16 PM UTC-4, klem kedidelhopper wrote:

I have to install an Internet connection at a location somewhat

removed from the origination point. The building is very large, spread

out, and difficult to run wire through. Presently there already is a

connection terminated in an Rj45 at a point that is only used for one

week out of every year. All other times there is nothing plugged into

this jack but the connection remains active. In order to make the

connection to the new location about 100 feet away can I tap off the

existing jack and "daisy chain" the wire to the new location and then

terminate that wire in a second R45? I now this is not common practice

but if only one computer is using the line at any particular time

would this work? There will never be a time that two computers will

ever be operating on this line at the same time although for that week

in question they both may be plugged into it though. would this be an

issue? I can arrange to have the new location unplugged during this

time if need be. Thanks for any advice. Lenny

Mike
I really like the idea of a plug on the extension wire. The existing jack is on a wall in a public building in a single gang lock box fed through 1/2 inch EMT. I can figure a way to arrange this so that the extension runs through another length of pipe into the same box and is then plugged into the existing jack and the box locked for the 51 weeks of the year that it isn't used. That way the remote location will be live for those 51 weeks. When they need to use the present location for that one week, they'll simply unlock the box, unplug the extension wire, (similar to what you do to test a CO line at a telephone interface Demarc point), thereby freeing up the line downstream. They can then connect their equipment without an issue. Great idea, Thanks, Lenny

 

[Allodoxaphobia]

On Sun, 30 Sep 2012 18:40:41 -0700, mike wrote:

On 9/30/2012 4:44 PM, klem kedidelhopper wrote:
I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45?
yes, but only one can be plugged in and it will be a nightmare
for the next guy who tries to figger out why it doesn't work like it
should. Put a plug on the extension wire so you can have only one
connected.

Stick an ethernet switch at the location and you can have as many
plugged in as you have ports on the switch.
They're $10 on ebay, free at garage sales.
If you walk outside in a populated area and yell, "I need an
ethernet swtich," people will come out of the woodwork glad to
get rid of them.
You only have to have the switch powered for a week.

Ethernet switches can also be found on the back of (unwanted) DSL modems
found on the shelves of second hand stores. Just put some black tape
over the blinking "DSL Fail" LED and you've got yourself an inexpensive
ethernet switch. Many DSL Modems come with 4-way switches. I did that
with an ActionTec DSL Modem for a few years, before I found a 10/100
5-Port LinkSys for $5 on a shelf at a second hand store.

HTH
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

 

[Jeff Liebermann]

On 1 Oct 2012 14:31:03 GMT, Allodoxaphobia
<knock_yourself_out@example.net> wrote:

Ethernet switches can also be found on the back of (unwanted) DSL modems
found on the shelves of second hand stores. Just put some black tape
over the blinking "DSL Fail" LED and you've got yourself an inexpensive
ethernet switch. Many DSL Modems come with 4-way switches. I did that
with an ActionTec DSL Modem for a few years, before I found a 10/100
5-Port LinkSys for $5 on a shelf at a second hand store.
HTH
Jonesy

I just ripped out almost exactly the same great idea and replaced it
with a proper ethernet switch.

No DSL modem comes with more than one ethernet port. The modem is a
bridge between DSL and ethernet and only requires one port each.
However, a DSL *ROUTER* will have a built in ethernet switch as you
describe. However, it will also have a DHCP server, NAT, RIP, and a
mess of other acronyms. If you don't turn these off on the
configuration page, you're going to have problems on the network. For
example, having a second DHCP server running on your LAN will create a
problem when a workstation decides to get its DHCP assigned IP address
from your DSL router, and finds the gateway address pointing to a
device that goes nowhere.

In my case, the DSL router was actually setup correctly with all the
extra services disabled. It also was working well for about a year.
Then, someone punched the reset button on the back of the DSL router,
and the problems started. Since nobody bothered to tell me that they
had added this device to the network, it took some sniffing to find
it.

Maybe some more black tape over the reset switch hole?
Or, just use the correct piece of hardware in the first place.

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

 

[Dave Platt]

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45? I now this is not common practice
but if only one computer is using the line at any particular time
would this work?

It would probably work OK when you connect something to the jack at
the end of the new run of wire.

It may very well *not* work, for devices plugged into the existing
jack, during that one week per year.

The problem is that your new run of wire will create an "un-terminated
stub" in the Ethernet transmission line. This is a no-no - signals
travelling down the wire (from the middle jack to the unused new end
jack) will arrive at the end jack, and will "see" an abrupt change in
the characteristic impedance of the line (jumping up from 100 ohms or
so in the twisted pair, to a very high impedance at the jack). The
signals will be reflected by this impedance discontinuity, and travel
back along the wires towards the existing (middle) jack. When they
arrive there, they will mix with (and interfere with) the signals from
the other end of the line, and it's very likely that the computed
plugged into this jack will see a completely garbled packet as a
result and will discard it.

This is essentially the same problem which can create "ghosts" in an
analog TV system, if you have an extra length of coax daisy-chained
from a coax port.

There are several ways to deal with this problem effectively.

The one I'd recommend (inexpensive, easy, and it should comply with
all of the standards and work fine): convert the existing outlet plate
from one RJ-45, to two RJ-45 jacks. Run the "tap" line to the new
location to the second RJ-45 on the new jack... do *not* hard-wire it
into the existing line or jack!

When you want to use the original location, plug the computer into
RJ-45 #1 (the one which goes to your central location). When you're
not using this location, and want to use the new location, simply plug
a short Ethernet jumper cable into the two RJ-45 jacks.

This approach can be extended to allow you to use both locations, at
low expense. Simply buy an inexpensive 10/100 switch (4- or 5-port
type) and place it at the existing location. Connect its upstream
port to jack #1. Connect jack #2 to one of its downstream ports.
When you want to use a computer at this location, simply connect it to
one of the other downstream ports on the switch... no need to
disconnect your new location.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

On Monday, October 1, 2012 2:44:30 PM UTC-4, Dave Platt wrote:

I have to install an Internet connection at a location somewhat >removed from the origination point. The building is very large, spread >out, and difficult to run wire through. Presently there already is a >connection terminated in an Rj45 at a point that is only used for one >week out of every year. All other times there is nothing plugged into >this jack but the connection remains active. In order to make the >connection to the new location about 100 feet away can I tap off the >existing jack and "daisy chain" the wire to the new location and then >terminate that wire in a second R45? I now this is not common practice >but if only one computer is using the line at any particular time >would this work? It would probably work OK when you connect something to the jack at the end of the new run of wire. It may very well *not* work, for devices plugged into the existing jack, during that one week per year. The problem is that your new run of wire will create an "un-terminated stub" in the Ethernet transmission line. This is a no-no - signals travelling down the wire (from the middle jack to the unused new end jack) will arrive at the end jack, and will "see" an abrupt change in the characteristic impedance of the line (jumping up from 100 ohms or so in the twisted pair, to a very high impedance at the jack). The signals will be reflected by this impedance discontinuity, and travel back along the wires towards the existing (middle) jack. When they arrive there, they will mix with (and interfere with) the signals from the other end of the line, and it's very likely that the computed plugged into this jack will see a completely garbled packet as a result and will discard it. This is essentially the same problem which can create "ghosts" in an analog TV system, if you have an extra length of coax daisy-chained from a coax port. There are several ways to deal with this problem effectively. The one I'd recommend (inexpensive, easy, and it should comply with all of the standards and work fine): convert the existing outlet plate from one RJ-45, to two RJ-45 jacks. Run the "tap" line to the new location to the second RJ-45 on the new jack... do *not* hard-wire it into the existing line or jack! When you want to use the original location, plug the computer into RJ-45 #1 (the one which goes to your central location). When you're not using this location, and want to use the new location, simply plug a short Ethernet jumper cable into the two RJ-45 jacks. This approach can be extended to allow you to use both locations, at low expense. Simply buy an inexpensive 10/100 switch (4- or 5-port type) and place it at the existing location. Connect its upstream port to jack #1. Connect jack #2 to one of its downstream ports. When you want to use a computer at this location, simply connect it to one of the other downstream ports on the switch... no need to disconnect your new location. -- Dave Platt <dplatt@radagast.org> AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!

Thanks for all the great ideas guys. I really appreciate them. Lenny

 

"No DSL modem comes with more than one ethernet port. "

Your posts indicate intelligence, are logical and all that, but this one time you erred. Claimed a negative. You know better.

Two 2WIRE modems I know (and actually did the setup) have four RJ45s as well as four channel 802.11. (g I think)

Of course you could argue that these are routers or whatever, but really fastforwarding through the argument which would be fruitless anyway, how different is it ? Isn't the DSL MODEM just a router or switch that connects to a "slightly" bigger network ?

Two ways of thinking about it but I think neither is wrong.

J

 

[Jeff Liebermann]

On Thu, 4 Oct 2012 04:41:52 -0700 (PDT), jurb6006@gmail.com wrote:

"No DSL modem comes with more than one ethernet port. "

Your posts indicate intelligence, are logical and all that, but this one time you erred. Claimed a negative. You know better.

Two 2WIRE modems I know (and actually did the setup) have four RJ45s as well as four channel 802.11. (g I think)

Give me a 2wire model number and my guess(tm) is that it will be
a router inside. All (and I do mean all) 2wire devices that have
built in wireless also have a router inside. Marketing may call is a
"modem", but if it has a router inside, it's really a "DSL router".

Of course you could argue that these are routers or whatever, but really fastforwarding through the argument which would be fruitless anyway, how different is it ? Isn't the DSL MODEM just a router or switch that connects to a "slightly" bigger network ?

Not bigger network, but different network. The definition of a router
is a device that connects two DIFFERENT networks at the IP layer (ISO
layer 3). One port is connected to the greater internet network. The
other port is connected to a local area network, that uses
non-routeable IP addresses.

My definitions, which might be different than yours:

DSL Modem: DSL (actually ATM) to ethernet bridge. Everything done at
the MAC layer (ISO Layer 2) with no involvement with IP layer (ISO
layer 3) except for configuration management.

DSL Router: Contains a DSL modem where the ethernet port is connected
to an internal router. Always includes NAT/PAT to allow a single IP
address to serve multiple non-routeable IP addresses on the LAN. The
modem works on the MAC layer, while the router works on the IP layer.
A 5 port (yes 5 ports, not 4) ethernet switch on the router output
allows connections with additional devices. If an optional internal
wireless access point is included, it connects to the 5th ethernet
port allowing additional connections.

Not the greatest definition, but I think it will suffice.

Two ways of thinking about it but I think neither is wrong.
J

Only two ways? In the distant past, I tried to reconcile the various
names for wireless ethernet bridges and gave up. Too much naming
creativity in an industry that can't even get NAT and PAT correct.
<http://wireless.navas.us/index.php?title=Wi-Fi#Wireless_Bridge_Types>
With that much creative naming, I don't want to even think about
cleaning up the descriptions of the various wireless access point,
routers, bridges, gateways, switches, media servers, etc.

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

 

[josephkk]

On Sun, 30 Sep 2012 16:44:16 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I have to install an Internet connection at a location somewhat
removed from the origination point. The building is very large, spread
out, and difficult to run wire through. Presently there already is a
connection terminated in an Rj45 at a point that is only used for one
week out of every year. All other times there is nothing plugged into
this jack but the connection remains active. In order to make the
connection to the new location about 100 feet away can I tap off the
existing jack and "daisy chain" the wire to the new location and then
terminate that wire in a second R45? I now this is not common practice
but if only one computer is using the line at any particular time
would this work? There will never be a time that two computers will
ever be operating on this line at the same time although for that week
in question they both may be plugged into it though. would this be an
issue? I can arrange to have the new location unplugged during this
time if need be. Thanks for any advice. Lenny

The real issue is line length to the next device. 100 meters or 320 feet
depending typical local units. Beyond that function is NOT guaranteed by
the standards. Non-compliant cables, connectors or other connections may
interfere with reliable as well.

?-)

 

[josephkk]

On Thu, 04 Oct 2012 09:20:07 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

Not bigger network, but different network. The definition of a router
is a device that connects two DIFFERENT networks at the IP layer (ISO
layer 3). One port is connected to the greater internet network. The
other port is connected to a local area network, that uses
non-routeable IP addresses.

I mostly agree with your distinction on the difference between modem and
router.

My definitions, which might be different than yours:

DSL Modem: DSL (actually ATM) to ethernet bridge. Everything done at
the MAC layer (ISO Layer 2) with no involvement with IP layer (ISO
layer 3) except for configuration management.

I do not think that what is appearing at the DSL end user terminals is ATM
but closer to VT45 or VT135 with highly compressed data. Moreover you are
looking at data likely being a shared service with a much more broadband
(TV) type service on the same pair.

?-)

 

[Jeff Liebermann]

On Thu, 04 Oct 2012 21:25:59 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

On Thu, 04 Oct 2012 09:20:07 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:


Not bigger network, but different network. The definition of a router
is a device that connects two DIFFERENT networks at the IP layer (ISO
layer 3). One port is connected to the greater internet network. The
other port is connected to a local area network, that uses
non-routeable IP addresses.

I mostly agree with your distinction on the difference between modem and
router.

It's an oversimplified definition, which falls apart on devices like a
brouters (bridge-router) and using a DSL modem to simultaneously
connect to multiple services. Simple definitions never seem to stay
simple.

My definitions, which might be different than yours:

DSL Modem: DSL (actually ATM) to ethernet bridge. Everything done at
the MAC layer (ISO Layer 2) with no involvement with IP layer (ISO
layer 3) except for configuration management.

I do not think that what is appearing at the DSL end user terminals is ATM
but closer to VT45 or VT135 with highly compressed data. Moreover you are
looking at data likely being a shared service with a much more broadband
(TV) type service on the same pair.

?-)

Ok, you got me. What is V45 and V135? Google wasn't particularly
helpful by suggesting that VT meant vacuum tube. Are you thinking of
AT&T U-Verse IPTV service which uses VDSL? If so, I know nothing
because AT&T doesn't offer it in my area.

The DSL modem with diagnostics include "ATM Ping" which should be a
clue. Articles on how DSL works always mention ATM as the underlying
virtual circuit mechanism to connect to the DSLAM (ATM switch) which
does the IP packet reassembly from the tiny ATM pieces.
<http://www.eetimes.com/electronics-news/4140135/ADSL-Technology-Explained-Part-2-Getting-to-the-Application-Layer>
See section "ADSL and ATM".

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

 

[josephkk]

On Fri, 05 Oct 2012 09:12:14 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Thu, 04 Oct 2012 21:25:59 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

On Thu, 04 Oct 2012 09:20:07 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:


Not bigger network, but different network. The definition of a router
is a device that connects two DIFFERENT networks at the IP layer (ISO
layer 3). One port is connected to the greater internet network. The
other port is connected to a local area network, that uses
non-routeable IP addresses.

I mostly agree with your distinction on the difference between modem and
router.

It's an oversimplified definition, which falls apart on devices like a
brouters (bridge-router) and using a DSL modem to simultaneously
connect to multiple services. Simple definitions never seem to stay
simple.

My definitions, which might be different than yours:

DSL Modem: DSL (actually ATM) to ethernet bridge. Everything done at
the MAC layer (ISO Layer 2) with no involvement with IP layer (ISO
layer 3) except for configuration management.

I do not think that what is appearing at the DSL end user terminals is ATM
but closer to VT45 or VT135 with highly compressed data. Moreover you are
looking at data likely being a shared service with a much more broadband
(TV) type service on the same pair.

?-)

Ok, you got me. What is V45 and V135? Google wasn't particularly
helpful by suggesting that VT meant vacuum tube. Are you thinking of
AT&T U-Verse IPTV service which uses VDSL? If so, I know nothing
because AT&T doesn't offer it in my area.

VT45 is the payload portion of an STS-1 (about equal to a DS-3), likewise
VT135 is the payload portion of an STS-3.

The DSL modem with diagnostics include "ATM Ping" which should be a
clue. Articles on how DSL works always mention ATM as the underlying
virtual circuit mechanism to connect to the DSLAM (ATM switch) which
does the IP packet reassembly from the tiny ATM pieces.
http://www.eetimes.com/electronics-news/4140135/ADSL-Technology-Explained-Part-2-Getting-to-the-Application-Layer
See section "ADSL and ATM".

Thanks for the link. It ties up a lot of loose ends for me. But the
signal coming down the wire to my modem-router does not seem to include
the ATM overhead.

?-)

 

"Give me a 2wire model number and my guess(tm) is that it will be
a router inside. All (and I do mean all) 2wire devices that have
built in wireless also have a router inside. Marketing may call is a
"modem", but if it has a router inside, it's really a "DSL router". "

It's a 2WIRE RG2701HG-00. One link calls it a modem and switch, another a modem switch/router and another a modem/router.

Talk about definitions.

In the old days I got the gist of electronics, and I mean to where I could do a little bitt of designing. That was all analog. Even then some of the definitions were not memorized by me, like even though I know the names Colpitts and Hartley I couldn't tell you the (dis)advantages of either right now. I can look it up of course but I really only committ(ed) to memory what I need(ed).

I see no difference between a switch and a router, but of course there is.

What I see is that a router can have a hardware firewall, but I've never seen it on a switch. I may need to know these things soon if I go to get the network at work running again.

I know where to come.

J

 

[Jeff Liebermann]

On Sun, 07 Oct 2012 10:48:46 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

The DSL modem with diagnostics include "ATM Ping" which should be a
clue. Articles on how DSL works always mention ATM as the underlying
virtual circuit mechanism to connect to the DSLAM (ATM switch) which
does the IP packet reassembly from the tiny ATM pieces.
http://www.eetimes.com/electronics-news/4140135/ADSL-Technology-Explained-Part-2-Getting-to-the-Application-Layer
See section "ADSL and ATM".

Thanks for the link. It ties up a lot of loose ends for me. But the
signal coming down the wire to my modem-router does not seem to include
the ATM overhead.

Note that the article was from 2001. That was intentional as
improvements and additions to DSL have added some complexity.

ATM overhead is the "ATM Tax". With 5 extra bytes of header for every
53 bytes of payload, that's:
5/53 = 9.4%
of overhead. The ATM Tax and the additional header overhead for
various layers totals about 15% which is why a 1.5Mbit/sec DSL line
actually delivers only 1.3Mbits/sec.

The header include the VCI (virtual circuit identifier) so that the
packets can be disassembled into multiple VC's (virtual circuits),
thus allowing a single DSL modem to support multiple IP data streams.
DSL could theoretically connect to multiple ISP's at the same time,
over the same phone line, but AT&T doesn't allow that in the US.

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

 

[Jeff Liebermann]

On Sun, 7 Oct 2012 12:34:53 -0700 (PDT), jurb6006@gmail.com wrote:

It's a 2WIRE RG2701HG-00. One link calls it a modem and switch,
another a modem switch/router and another a modem/router.
Talk about definitions.

I think you see the problem.

I have a pile of 2701HG wireless routers in the office. The routers
work fine, but the power supplies suck.
<http://802.11junk.com/jeffl/pics/repair/slides/2Wire-power-supplies.html>
<http://802.11junk.com/jeffl/pics/repair/slides/2Wire-power-supply.html>
Fortunately, they're easy to crack open and repair. When yours quits,
reboots erratically, or acts weird, crack open the PS and fix it
rather than tossing the router.

Incidentally, try:
<http://192.168.1.254/mdc>
on your 2701HG.
<http://www.dslreports.com/faq/twowire/10._Troubleshooting>

The 2701HG routers have an additional problem in that it is impossible
to update the firmware. I've identified about 12 different firmware
versions with little clue as to the differences. Now that 2-wire is
part of Pace, they won't even talk to me about firmware. Fortunately,
the most disgusting problem (failure to reconnect after connecting to
another access point with Apple iPads) isn't very common. Also,
there's no way to save the restore the settings, so everyone needs to
be setup from scratch. Still, I kinda like them (probably the white
color).

Anyway, if you want to be technically correct, the description has to
include all the major features. So the 2710HG would be a:
"DSL modem wireless firewall IP router and switch". Somehow, I don't
think marketing would like that.

In the old days I got the gist of electronics, and I mean to where I
could do a little bitt of designing. That was all analog. Even then
some of the definitions were not memorized by me, like even though
I know the names Colpitts and Hartley I couldn't tell you the
(dis)advantages of either right now. I can look it up of course
but I really only committ(ed) to memory what I need(ed).

The old daze are gone. I read sci.electronics.repair and must admit
that I have never heard of some of the devices, acronyms,
nomenclature, software, etc. So, I use Google to search for clues,
read what I find, and sometimes actually learn something new. I
suggest you do the same.

I see no difference between a switch and a router, but of course there is.

Easy. A switch works at the MAC address layer. It directs packets
based on the destination MAC address. No IP addresses are involved.

A router connects two different IP networks and works on the IP layer.
It directs packets based on the destination IP address. Although the
MAC layer is involved, no MAC addresses are passed through a router.

All 802.11 wireless works on the MAC address layer. Packets are
directed by the destination MAC address layer. With an encrypted
wireless network, these MAC addresses are sent unencrypted and can be
easily sniffed. However, the relevant IP addresses, encapsulated and
encrypted inside 802.11 packets, are not sniffable.

Also, a bridge is a two port ethernet switch.

What I see is that a router can have a hardware firewall, but I've
never seen it on a switch. I may need to know these things soon
if I go to get the network at work running again.

Firewalls work on the IP layer and therefore require a router.

I know where to come.

Groan. There are better newsgroups and forums to obtain information
on networking.

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