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VoOP over DSL problems and solutions?

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Anonymous
February 14, 2005 3:18:39 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

My small company has ADSL through Pacbell, which we are using for VoIP.
Sometimes you will be talking to someone and they will have trouble hearing
us. The opposite never happens.

We think it is because our upload does not provide us with reliable
bandwidth.

We were thinking that switching to SDSL would help. Any thoughts both on the
problem and whether you think switching to SDSL might help? Is SDSL a
different, more reliable technology? It certainly is priced higher than
ADSL.


thanks.

--
Robert Anderson
Anonymous
February 14, 2005 7:10:35 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

In comp.dcom.voice-over-ip Robert Anderson <rbanderson@nospamnwlink.com> wrote:
: My small company has ADSL through Pacbell, which we are using for VoIP.
: Sometimes you will be talking to someone and they will have trouble hearing
: us. The opposite never happens.

: We think it is because our upload does not provide us with reliable
: bandwidth.

It certainly sounds like your outgoing link could be congested. Your
ADSL equipment may have counters that you can access that will help you
decide. Look for dropped packets and/or lot of packets being queued to
send.

: We were thinking that switching to SDSL would help. Any thoughts both on the
: problem and whether you think switching to SDSL might help? Is SDSL a
: different, more reliable technology? It certainly is priced higher than
: ADSL.

Reliability for either is probably close to the same, but it sounds like
your problem is related to a *full* pipe rather than an *unreliable* one.
See if your service provider can provide for more upstream bandwidth (as
ADSL or SDSL). That will probably solve your problem.
Anonymous
February 15, 2005 3:05:26 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

In comp.dcom.xdsl Robert Anderson <rbanderson@nospamnwlink.com> wrote:
> My small company has ADSL through Pacbell, which we are using
> for VoIP. Sometimes you will be talking to someone and they
> will have trouble hearing us. The opposite never happens.

> We think it is because our upload does not provide us with
> reliable bandwidth.

Are you sure your uplink isn't saturated? Somebody serving out
pages or P2P? ADSL often underprovides uplink. Sniffer time!

-- Robert
Related resources
Anonymous
February 15, 2005 12:15:48 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

Increasing your outgoing bandwidth with SDSL or a speed change of your ADSL
is a temporary fix. More bandwidth fixes everything in the short term.



What you want to implement is QoS, giving your VoIP traffic a higher
priority over all other outbound traffic. A simple TOS bit should be
sufficient, and most VoIP

hard-phones already set the TOS bit to a higher priority.



If the xDSL is your aggregate device, PacBell may not allow you to turn QoS
on in their modem. So you may need another router in front of the xDSL to
use QoS.



Just remember that this will not improve end to end traffic. QoS will be
ignored by any device that is not configured to use it. The priority will
not be used throughout the PacBell network, it will be ignored past the
aggregation point.

"Robert Anderson" <rbanderson@nospamnwlink.com> wrote in message
news:11121tfd7vi9f0e@corp.supernews.com...
> My small company has ADSL through Pacbell, which we are using for VoIP.
> Sometimes you will be talking to someone and they will have trouble
> hearing us. The opposite never happens.
>
> We think it is because our upload does not provide us with reliable
> bandwidth.
>
> We were thinking that switching to SDSL would help. Any thoughts both on
> the problem and whether you think switching to SDSL might help? Is SDSL a
> different, more reliable technology? It certainly is priced higher than
> ADSL.
>
>
> thanks.
>
> --
> Robert Anderson
>
Anonymous
February 15, 2005 5:35:02 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

On Mon, 14 Feb 2005 12:18:39 -0800, "Robert Anderson"
<rbanderson@nospamnwlink.com> wrote:

>My small company has ADSL through Pacbell, which we are using for VoIP.
>Sometimes you will be talking to someone and they will have trouble hearing
>us. The opposite never happens.

Personally, I've found that using VoIP through a provider that's a
company other than the one you also use for access makes for
unreliablity. To explain, I have VoIP through Time Warner, who's also
my cable and ISP provider. My VoIP connection is flawless and the
quality is great.

A person who I work with on projects has a VoIP connection through
another provider and his connection is garbage. He cuts out
continually and has to call me back on a cell phone.

I realize this is only one example, but I really do think that quality
is the reason all the forecasts are saying that cable providers are
going to come to dominate VoIP. They have the network and
connectivity, along with technical expertise, to make it happen.
Anonymous
February 15, 2005 5:35:03 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

Cyrus Afzali wrote:
....
> Personally, I've found that using VoIP through a provider that's a
> company other than the one you also use for access makes for
> unreliablity. To explain, I have VoIP through Time Warner, who's also
> my cable and ISP provider. My VoIP connection is flawless and the
> quality is great.
>
> A person who I work with on projects has a VoIP connection through
> another provider and his connection is garbage. He cuts out
> continually and has to call me back on a cell phone.
>

I 'hear' that some VoIP providers use compression algorithms that do not
work well with the compression/decompression algorithms on the other end!

> I realize this is only one example, but I really do think that quality
> is the reason all the forecasts are saying that cable providers are
> going to come to dominate VoIP. They have the network and
> connectivity, along with technical expertise, to make it happen.
>

That could come true for a varity of reasons, e.g. LD issues vanish!
Anonymous
February 15, 2005 9:02:44 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

"Brian LaVallee" <poing@REMOVE-NO_SPAM-THIS.comcast.net> writes:
> If the xDSL is your aggregate device, PacBell may not allow you to turn QoS
> on in their modem. So you may need another router in front of the xDSL to
> use QoS.

Putting a router (or NAT box) in front of the dsl modem won't solve
much. The dsl modem has packet buffers inside it. If your uplink is
saturated, even briefly, this packet buffer is going to be stuffed
with full of other, low-priority traffic. Sure the packets were
ordered when they left the QoS capable router (or nat box), but after
the voip packets got loaded into the dsl modem, the other packets were
stuffed in there until no more fit. The next voip packet that hits
the dsl modem is going to be dropped. If you need QoS on your uplink,
the only place it is going to work is in the last buffer *right*
before your choke-point. That choke point is inside the dsl modem.

Think of it this way, the local router's connection to your dsl modem
is going to be either 10Mbits/sec or 100Mbits/sec. There is always
going to be bandwidth on this link to shove packets at the dsl modem.
The choke point is the dsl uplink which is going to be 128kbits/sec to
600kbits/sec typically. The local router is going to be able to shove
packets in at a much higher rate than they can drain out. The dsl
modem's output buffers for the dsl uplink are going to be packed full.

The only way to do meaningful QoS is to do the final QoS reordering in
the modem itself.

-wolfgang
--
Wolfgang S. Rupprecht http://www.wsrcc.com/wolfgang/
Hate software patents? Sign here: http://thankpoland.info/
Anonymous
February 16, 2005 8:04:12 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

Wolfgang S. Rupprecht wrote:

>
> Putting a router (or NAT box) in front of the dsl modem won't solve
> much.

No. Putting a router (REAL router, not a nat box) in there WOULD resolve
the issue if it was set up properly. a decent router is going to have
several megs of cache and the ability to specify the ougoing line rate.
So if the dsl line has a 384kbps uplink speed, you set the router to
limit outgoing packets to that rate. Then the router only sends 284kb of
data per second to the dsl modem. You would likely get some of the lower
priority packets dropped, but of cours ethat is exactly what you want to
have happen in this case.

> The dsl modem has packet buffers inside it. If your uplink is
> saturated, even briefly, this packet buffer is going to be stuffed
> with full of other, low-priority traffic. Sure the packets were
> ordered when they left the QoS capable router (or nat box), but after
> the voip packets got loaded into the dsl modem, the other packets were
> stuffed in there until no more fit. The next voip packet that hits
> the dsl modem is going to be dropped. If you need QoS on your uplink,
> the only place it is going to work is in the last buffer *right*
> before your choke-point. That choke point is inside the dsl modem.
>
> Think of it this way, the local router's connection to your dsl modem
> is going to be either 10Mbits/sec or 100Mbits/sec. There is always
> going to be bandwidth on this link to shove packets at the dsl modem.
> The choke point is the dsl uplink which is going to be 128kbits/sec to
> 600kbits/sec typically. The local router is going to be able to shove
> packets in at a much higher rate than they can drain out. The dsl
> modem's output buffers for the dsl uplink are going to be packed full.
>
> The only way to do meaningful QoS is to do the final QoS reordering in
> the modem itself.

wrong.

>
> -wolfgang
Anonymous
February 17, 2005 2:42:13 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.xdsl (More info?)

"T. Sean Weintz" <strap@hanh-ct.org> writes:
> Wolfgang S. Rupprecht wrote:
>
>> Putting a router (or NAT box) in front of the dsl modem won't solve
>> much.
>
> No. Putting a router (REAL router, not a nat box) in there WOULD
> resolve the issue if it was set up properly. a decent router is going
> to have several megs of cache and the ability to specify the ougoing
> line rate. So if the dsl line has a 384kbps uplink speed, you set the
> router to limit outgoing packets to that rate. Then the router only
> sends 284kb of data per second to the dsl modem. You would likely get
> some of the lower priority packets dropped, but of cours ethat is
> exactly what you want to have happen in this case.

What you propose doesn't allow you to send 384kbps out of your
384kbit/sec DSL connection. Using your own numbers you end up only
getting 284kb -- if it works.

Like I said, if you want to have your voip packets moved to the head
of the queue when the uplink is saturated (eg. 384kbits are being sent
up the 384kbit/sec link) then you'd better have the TOS logic right
before the choke point.

If you want to keep the modem unsaturated by throwing away 1/4 of your
bandwidth then we clearly aren't talking about using the whole link
are we? We are talking about some hack that only lets you use 3/4s of
it.

-wolfgang
--
Wolfgang S. Rupprecht http://www.wsrcc.com/wolfgang/
Hate software patents? Sign here: http://thankpoland.info/
!