ATM QoS type and PCR/SCR/MBS, what to set them to?

My Zyxel routers both have an 'ATM QoS type' setting and settings for
PCR (Peak Cell Rate), SCR (Sustain Cell Rate) and MBS (Maximum Burst
Size) in the Internet Access Setup.

The Zyxel help (and my searches around the internet) have told me a
bit more about what these mean but don't give me a clue about what to
set them to for a 'general use' internet connection.

Our ADSL gets used for:-

Interactive ssh to command line utilities on remote systems.

The usual web browsing etc.

Downloads using FTP and (low priority) bittorrent.

Various other things I've forgotten about I expect.

VIOP SIP phone connections.

Occasional streaming audio and such.


This would seem to need a mix of settings according to the use, what's
the best compromise?

--
Chris Green

(E-Mail Removed) wrote:
> My Zyxel routers both have an 'ATM QoS type' setting and settings for
> PCR (Peak Cell Rate), SCR (Sustain Cell Rate) and MBS (Maximum Burst
> Size) in the Internet Access Setup.
>
> The Zyxel help (and my searches around the internet) have told me a
> bit more about what these mean but don't give me a clue about what to
> set them to for a 'general use' internet connection.
>
> Our ADSL gets used for:-
>
> Interactive ssh to command line utilities on remote systems.
>
> The usual web browsing etc.
>
> Downloads using FTP and (low priority) bittorrent.
>
> Various other things I've forgotten about I expect.
>
> VIOP SIP phone connections.
>
> Occasional streaming audio and such.
>
>
> This would seem to need a mix of settings according to the use, what's
> the best compromise?
>
Can no one even suggest a web site that might help with this?

--
Chris Green

(E-Mail Removed) wrote:
> (E-Mail Removed) wrote:
> > My Zyxel routers both have an 'ATM QoS type' setting and settings for
> > PCR (Peak Cell Rate), SCR (Sustain Cell Rate) and MBS (Maximum Burst
> > Size) in the Internet Access Setup.
> >
> > The Zyxel help (and my searches around the internet) have told me a
> > bit more about what these mean but don't give me a clue about what to
> > set them to for a 'general use' internet connection.
> >
> > Our ADSL gets used for:-
> >
> > Interactive ssh to command line utilities on remote systems.
> >
> > The usual web browsing etc.
> >
> > Downloads using FTP and (low priority) bittorrent.
> >
> > Various other things I've forgotten about I expect.
> >
> > VIOP SIP phone connections.
> >
> > Occasional streaming audio and such.
> >
> >
> > This would seem to need a mix of settings according to the use, what's
> > the best compromise?
> >
> Can no one even suggest a web site that might help with this?
>
> --
> Chris Green

For an ADSL Intenet connection these values won't have any effect. ATM
QoS settings are per PVC and as you only have one PVC you would have
the same QoS for all traffic. Secondly as it is ATM QoS, once the
traffic hits the Internet it won't apply anyway because the Internet
traffic is IP not ATM. In the case of ADSL, ATM is only the layer 2
transport from the router to the DSLAM and partway into the backhaul
depending on your ISP, any QoS/CoS is at layer 3 - IP.

BH

(E-Mail Removed) wrote:
> (E-Mail Removed) wrote:
> > (E-Mail Removed) wrote:
> > > My Zyxel routers both have an 'ATM QoS type' setting and settings for
> > > PCR (Peak Cell Rate), SCR (Sustain Cell Rate) and MBS (Maximum Burst
> > > Size) in the Internet Access Setup.
> > >
> > > The Zyxel help (and my searches around the internet) have told me a
> > > bit more about what these mean but don't give me a clue about what to
> > > set them to for a 'general use' internet connection.
> > >
> > > Our ADSL gets used for:-
> > >
> > > Interactive ssh to command line utilities on remote systems.
> > >
> > > The usual web browsing etc.
> > >
> > > Downloads using FTP and (low priority) bittorrent.
> > >
> > > Various other things I've forgotten about I expect.
> > >
> > > VIOP SIP phone connections.
> > >
> > > Occasional streaming audio and such.
> > >
> > >
> > > This would seem to need a mix of settings according to the use, what's
> > > the best compromise?
> > >
> > Can no one even suggest a web site that might help with this?
> >
>
> For an ADSL Intenet connection these values won't have any effect. ATM
> QoS settings are per PVC and as you only have one PVC you would have
> the same QoS for all traffic. Secondly as it is ATM QoS, once the
> traffic hits the Internet it won't apply anyway because the Internet
> traffic is IP not ATM. In the case of ADSL, ATM is only the layer 2
> transport from the router to the DSLAM and partway into the backhaul
> depending on your ISP, any QoS/CoS is at layer 3 - IP.
>
Thanks, excellent stuff, it has basically 'filled in the holes' so
that the other bits I have read make more sense now. However it does
raise one more question - why are these settings in my ADSL router at
all? Do VPN circuits count as PVCs, if so that would explain it a
bit.

--
Chris Green

[SNIP]

> Thanks, excellent stuff, it has basically 'filled in the holes' so
> that the other bits I have read make more sense now. However it does
> raise one more question - why are these settings in my ADSL router at
> all? Do VPN circuits count as PVCs, if so that would explain it a
> bit.
>
> --
> Chris Green

Think of a PVC as a fixed circuit like a leased line. A PVC is a
connection from point A to point B, in the case of ADSL point A is the
customer router and point B is BT's (or Bulldogs or Easynets) network.

It is technically possible to have multiple PVCs so for example from
the same router you could have a PVC to ISP-A and one to ISP-B (and all
the way to ISP-Z if you wanted). However, for whatever reason only one
PVC is available with UK broadband although some BT services do allow
multiple PVCs on ADSL access but these are expensive business only
services. In countries (can't think of one off hand) or business
services where multiple PVCs are available then these settings come
into play although they have to be supported by the ISP as they need to
be set at both ends of the link.



BH

(E-Mail Removed) wrote:
> [SNIP]
>
> > Thanks, excellent stuff, it has basically 'filled in the holes' so
> > that the other bits I have read make more sense now. However it does
> > raise one more question - why are these settings in my ADSL router at
> > all? Do VPN circuits count as PVCs, if so that would explain it a
> > bit.
> >
> > --
> > Chris Green
>
> Think of a PVC as a fixed circuit like a leased line. A PVC is a
> connection from point A to point B, in the case of ADSL point A is the
> customer router and point B is BT's (or Bulldogs or Easynets) network.
>
> It is technically possible to have multiple PVCs so for example from
> the same router you could have a PVC to ISP-A and one to ISP-B (and all
> the way to ISP-Z if you wanted). However, for whatever reason only one
> PVC is available with UK broadband although some BT services do allow
> multiple PVCs on ADSL access but these are expensive business only
> services. In countries (can't think of one off hand) or business
> services where multiple PVCs are available then these settings come
> into play although they have to be supported by the ISP as they need to
> be set at both ends of the link.
>
OK, thanks, excellent stuff, it's all fairly clear now.

The router help, just like most help, doesn't cover any of this, it
just gives the detail of what each setting does without any help as to
*why* you might want to change it.

--
Chris Green