From: Brian Lodwick (xpranax@xxxxxxxxxxx)
Date: Thu Oct 18 2001 - 16:02:07 GMT-3
Thanks Neill, I appreciate it!
The document I have has exactly the commands you mentioned, except for when
doing VoIP over Frame-Relay it says to add the ip rtp header compression on
the interface, and frame-relay ip rtp priority 16384 16383 <bandwidth> on
the frame relay map-class.
>>>Brian
>From: "R.J.Neill Craven" <ncraven@cravenworks.com>
>To: "Brian Lodwick" <xpranax@hotmail.com>
>CC: ccielab@groupstudy.com
>Subject: Re: QOS configs
>Date: Thu, 18 Oct 2001 11:51:52 -0400
>
>10ms is 1/100 of a second, so the simple answer is you divide the CIR
>by 100 to find the Bc. Therefore, CIR 64000bps implies Bc of 640
>bits. Be sure to pick a fragment size which is consistent with the 10
>ms rule as well. For example, a 1500 byte packet takes 187.5 ms to
>process on a 64Kbps interface. Obviously, we cannot allow a big
>packet to block the head of the line for such a long time. Somewhat
>like you wanting to get cash from an ATM but the person currently at
>the machine reaches for an envelope. So you will want to make sure no
>fragment takes longer than 10 ms to transmit. For a 64Kbps interface,
>this is 80 bytes which coincidentally, is 640 bits. (The
>fragmentation rule is based on the clock rate of the interface; the
>Bc is based on the CIR. When the clock rate and the CIR are the same,
>the Bc and fragment size will be the same, but remember, Bc is in
>bits and fragment is in bytes.)
>
>For VoFR be sure to add the "frame-relay voice bandwidth" command,
>otherwise voice calls will fail. The default voice bandwidth is 0;
>unless you set it to a value (usually a multiple of 12000), you will
>not be able to set up any VoFR calls. Note, though, this command is
>not needed or wanted if you are carrying VoIP traffic over a Frame
>Relay network.
>
>But don't stop there. You should enforce traffic shaping (that is,
>not adaptively), and enable fair queueing. The following would be my
>recommendation for releases 12.0(7)XK and later. We use 12.1(2)T in
>our labs.
>
>interface serial 0
> ip address ...
> encapsulation frame-relay
> frame-relay traffic-shaping
> class ccie
>
>map-class frame-relay ccie
> frame-relay cir 64000
> frame-relay bc 640
> no frame-relay adaptive-shaping
> frame-relay fair-queue
> frame-relay fragment 80
> frame-relay voice bandwidth 48000 ! This is needed for VoFR
> ! but not for VoIP over FR
>
>By the way, you could attach the map-class to each DLCI instead and
>have different map-classes for different DLCIs if you needed to.
>
>Notice I have not configured Be. I don't want to borrow from my
>future "allowance" and then be forced to delay a voice packet because
>I had borrowed. Data works on the principle of "better late than
>never", but voice (or any real time traffic, for that matter)
>operates on the principle of "better never than late"; I want to pace
>myself.
>
>Cheers,
>Neill
>
>
>At 12:59 PM +0000 18/10/01, Brian Lodwick wrote:
>>Ron,
>> It sounds like you have quite a grasp on this information. I'd like
>>to run something by you and see if you can help clear something up
>>I've been having difficulties with?
>> In the best documentation I have found on VoIP over Frame-Relay QOS
>>it notes the ideal Tc value is 10ms. It also says that 10ms is the
>>lowest configurable value. I understand this is optimum because it
>>will provide for very small time gaps between packets. The problem I
>>am encountering is how to mathmatically calculate this formula.
>>I found something saying something saying it was Tc = Bc/CIR
>>But then it goes on to say In this example we have a CIR to 64000,
>>and have set the Bc to 600 (forcing the Tc to it's minumum
>>configurable value)
>>Wouldn't that give you a Tc of 106.66....?
>>
>>>>>Brian
>>
>>>From: "Ron Royston" <ccie6824@hotmail.com>
>>>Reply-To: "Ron Royston" <ccie6824@hotmail.com>
>>>To: John.K.Feuerherd@WellsFargo.COM, ccielab@groupstudy.com
>>>Subject: Re: QOS configs
>>>Date: Wed, 17 Oct 2001 17:20:20 -0500
>>>
>>>No. I believe they are different. Scott Keagy talks about this in
>>>"Integrating Voice and Data Networks". CIR is typically expressed in Bps
>>>and is the AVERAGE rate of traffic guaranteed by the carrier; Bc and Be
>>>are
>>>expressed per unit of time, Tc, and are the ACTUAL number of bits that
>>>the
>>>carrier commits to transport. Cisco routers take CIR as Bps, and Bc as
>>>Bits.
>>>
>>>The only practical reason that you should use the latter of your examples
>>>is
>>>to malipulate the value of Tc, which plays an important role in
>>>controlling
>>>pausing time (which can manifest itself as jitter and delay in real-time
>>>apps.) You don't explicitly configure Tc, you configure Bc and CIR and
>>>IOS
>>>implies the Tc from there.
>>>
>>>I believe that these are the same (note the Be, not Bc):
>>>
>>>map-class frame-relay sample1
>>> frame-relay traffic-rate 9600 19200
>>> no frame-relay adaptive-shaping
>>>-and-
>>>map-class frame-relay sample2
>>> frame-relay cir 9600
>>> frame-relay be 19200
>>>
>>>Having the bc set to 19200, as in your example, would double the Tc to 2
>>>seconds, telling the router to push out 2xCIR bits every 2 seconds at the
>>>port speed. If the port speed is high, and the CIR low, your data gets
>>>sent
>>>in short bursts followed by a long pauses and will likely exceed your CIR
>>>from the carriers vantage point. The carrier's Tc is less than 2
>>>seconds,
>>>so they'll be getting 2 seconds worth of bits in less than 1 second if
>>>your
>>>port speed is high enough, and they'll De, discard eligible, that data.
>>>Right?
>>>
>>>-Ron
>>>
>>>PS IMHO, CCO needs more understandable info on this subject, but you can
>>>check out, http://www.cisco.com/warp/customer/125/21.shtml. That's all I
>>>can find.
>>>
>>>
>>>
>>>
>>>>From: John.K.Feuerherd@WellsFargo.COM
>>>>Reply-To: John.K.Feuerherd@WellsFargo.COM
>>>>To: ccielab@groupstudy.com
>>>>Subject: QOS configs
>>>>Date: Tue, 16 Oct 2001 19:56:49 -0700
>>>>
>>>>Hello all,
>>>> I have a quick question about traffic shaping. I think I understand
>>>>this, but I just want to make sure:
>>>>
>>>>This two configs are basically the same right.....
>>>>
>>>>map-class frame-relay sample1
>>>> frame-relay traffic-rate 9600 19200
>>>> no frame-relay adaptive-shaping
>>>>
>>>>
>>>>map-class frame-relay sample2
>>>> frame-relay cir 9600
>>>> frame-relay bc 19200
>>>>
>>>>Thanks in advance!
>>>>
>>>>JF
>>>>John Feuerherd
>>>>Wells Fargo Bank
>>>>CCNP CCDP
>>>>1-505-766-6118 <- Office
>>>>1-505-301-1966 <- Cell
>>>>John.K.Feuerherd@Wellsfargo.com
>>>>MAC: Q2129-074
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