From: Albert Lu (albert_ccie@xxxxxxxxx)
Date: Wed Nov 21 2001 - 17:37:27 GMT-3
Scott,
I agree with what you are saying, in the real world you would always know
what the bandwidth you have is on the link. I'm justing saying in a lab
environment where you are using alot of back-to-back connections, and your
serial defaults to T1.
Looking at ISDN, it looks like the link gives you a 64k bandwidth from the
interface command. However, if you have both channels, don't you get bumped
up to 128k?
Albert
-----Original Message-----
From: Scott Morris [mailto:swm@emanon.com]
Sent: Wednesday, November 21, 2001 11:53 PM
To: 'Albert Lu'
Subject: RE: Simple Question on serial interfaces.
ANY time you are doing calculations that need to know real bandwidth.. ie.
routing protocol metrics, load-sharing stuff, CAR, traffic shaping, RSVP,
QoS... Any of that stuff that will make calculations based on the bandwidth
of the line. Then you need to have REAL bandwidth there.
Imaging a serial interface with a fractional T-1, only 128k configured on
it. You want to run VoIP, running G.711 (uncompressed). You will need to
reserve 80k of bandwidth per phone call (64k data + overhead).
Well, like a bad person, you configure your rsvp with no top end
reservation, figuring that gives you flexibility as you increase your t-1
speed, so you don't need to reconfigure stuff.
Well, your first call goes through, the router checks bandwidth and says,
yea, that's cool. Now the second call comes through... According to your
routers' calculations, you've only reserved 80k out of a 1544k line. So,
sure, bring it on! Plenty of calls. Reality is both calls will start to
suck badly.
Use the bandwidth command. It's good design documentation anyway!
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Albert Lu
Sent: Tuesday, November 20, 2001 10:50 PM
To: 'Duy Nguyen'; Charles.Conte@NASD.com
Cc: ccielab@groupstudy.com
Subject: RE: Simple Question on serial interfaces.
On the otherhand, it seems like serial links always default to a T1
1.544Mbps for routing protocol cost calculations.
Another question that has been in the back of my mind is that when should
the bandwidth statement be entered into the interface? From various labs
(eg. fatkid), and sources they say that it is a good idea to always include
the bandwidth statement for all WAN interfaces (FR, Ser, BRI, ATM). But if
there were no specifications for what bandwidth to put on the interfaces,
then what can you do?
I guess if the bandwidth statement was left off, then they would default to
T1 and that should be ok.
Albert
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Duy Nguyen
Sent: Wednesday, November 21, 2001 2:02 PM
To: Charles.Conte@NASD.com
Cc: ccielab@groupstudy.com
Subject: Re: Simple Question on serial interfaces.
whatever you assign the clockrate, that's your total bandwidth. Try to do
tftp w/ 128k than try w/ 2048k you will see the difference. clockrate=bw.
Absolutely Positively Continuously Sincerely,
Duy Nguyen CCNP/CCIE written
net_port@hotmail.com
Cell (817) 707-7451
>From: "Conte, Charles" <Charles.Conte@NASD.com>
>Reply-To: "Conte, Charles" <Charles.Conte@NASD.com>
>To: "'ccielab@groupstudy.com'" <ccielab@groupstudy.com>
>Subject: Simple Question on serial interfaces.
>Date: Tue, 20 Nov 2001 20:31:14 -0500
>
>All,
>
> I have a real stupid question. Anyways to find out what the serial
>interface clockrate what do I have to do. Can I assume that whatever it
>assigns as BW is what the clockrate is set at. I don't think this is true
>because I configured my IGX to run on the clockrate of 2048. Maybe I
>missed
>it when I did the show controller command or show int serial command, but
>help me out guys.
>
>Charles
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