From: omar guarisco (oguarisco44@xxxxxxxxxxx)
Date: Tue Jan 08 2002 - 19:14:59 GMT-3
thnks to all for the reply....
Omar
>From: "Harris, Joe F" <Joe_Harris@AIMFUNDS.COM>
>Reply-To: "Harris, Joe F" <Joe_Harris@AIMFUNDS.COM>
>To: Jim Brown <Jim.Brown@CaseLogic.com>, "'omar guarisco'"
><oguarisco44@hotmail.com>, ccielab@groupstudy.com
>Subject: RE: FRTS ...CIR vs. MinCIR command
>Date: Mon, 7 Jan 2002 17:48:17 -0600
>
>If traffic shaping is enabled the router will check to see if there is
>credit built up so it can transmit the packet. If there is no credit
>available, the router queues the packet to whatever queue has been set up
>for that virtual circuit, such as First In/First Out (FIFO), Custom
>Queuing,
>Priority Queuing, ect...If there is credit available, the router sends the
>packet to the output interface and deducts the packet size from the
>available credit. The router will start the "xmit" process on the interface
>and at this point the packet is forwarded. Of note here is that Priority
>Queuing and Custom Queuing queue sizes can be adjusted via the CLI, however
>the FIFO shaping queue on the VC defualts to 40 and cannot be changed. Now
>After every time interval (TC), which are measured in milliseconds, the
>router begins the a loop which will the following:
>
>1. The router will add the byte increment, which is Bc/8, to the available
>credit. The router then checks to see if there is available credit to send
>the packet from this virtual circuit. If so, the process dequeues a packet.
>
>2. It then checks the "qcount", which is the number of packets currently in
>the interface output queue, and saves the value that it recorded.
>
>3. Then the packet is sent to the output interface and starts the transmit
>process, It also charges the virtual circuit for this packet.
>
>4. Then the value of the "qcount" that was saved earlier is checked to see
>if it's greater than 0. If so, it breaks out of the loop. This output queue
>check is done in order to prevent one virtual circuit from overrunning the
>interface output queue and causing packets to be dropped.
>
>5. If the output queue count is zero, the router continues sending more
>packets until there is no more data to send, the VC has used all of its
>credit or the output queue becomes greater than zero.
>
>Now lets bring BECN responses into the picture. If a router receives any
>BECNs during the current time interval, it decreases the transmit rate by
>25%. The rate will continue to drop with each BECN (with a limit of one
>drop
>per time interval) until the traffic rate gets to the minimum acceptable
>incoming or outgoing committed information rate (MINCIR), once it reaches
>MINCIR is stops decreasing the transmit rate.
>
>Once the traffic rate has decreased, it takes 16 time intervals of
>receiving
>no BECNs to start to increase the traffic rate again. Traffic increases
>(Be+Bc)/16, or a better way of describing it is the byte limit that shows
>up
>in the "show traffic" and "show frame pvc xxx" divided by 16. So it takes
>much longer to get back to commited information rate (CIR) than it does to
>drop to MINCIR. This is similar to slow start in TCP/IP. One way you can
>make this length of time much shorter is to set "Be" 7 times the value of
>"Bc", which would ensure it gets back to CIR immediately after going
>through
>16 time intervals without a BECN. Now this traffic increase only occurs
>when
>traffic shaping is active, so if traffic shaping is not active, the
>transmit
>increment stays the same even if BECNs are not received.
>
>So here are some terms that are related to BECNs and to your original
>question:
>
>TC - The Bc/CIR time interval, this is the inernalized version of TC where
>the time interval can't exceed 125ms.
>
>CIR - This is the rate you want to send out at. this is not the same as the
>CIR you get from your service provider, unless you are not allowed to send
>above CIR and CIR is measured in bits per second.
>
>Bc - This is the amount of data to send out per each Tc interval and it is
>measured in bits.
>
>Be - This is the amount excess data allowed to be sent during the first
>time
>interval once credit is built up and is measured in bits.
>
>Mincir - Is the amount of data to be sent during periods of congestion and
>it defaults to one half of CIR.
>
>Interval - is an equation that equates to Bc/CIR, with the maximum size
>being 125ms.
>
>Byte increment - is another equation that equates to Bc/8 and it must be
>greater than 125.
>
>limit - equals byte increment + Be/8 and is measured in bytes.
>
>So if you put these together you get this. Suppose you have router with a
>physical port speed of 64KB. You purchase a 16KB CIR from your service
>provider. The provider tells you that you can data out onto the PVC up to
>port speed as long as there is no congestion in their network, but that
>when
>there is congestion they will guarantee only CIR on the PVC. So in this
>case
>your frame relay configuration would look something like:
>
>int serial3/0
>ip address 192.168.10.1 255.255.255.252
>encap frame
>frame-relay traffic-shaping
>frame-relay map ip 192.1678.10.2 100 broadcast
>frame-relay interface-dlci 100 class shaping
>!
>!
>map-class frame-relay shaping
> frame-relay cir 64000
> frame-relay bc 8000
> frame-relay be 0
> frame-relay mincir 16000
>
>
>With traffic shaping, TC = Bc/CIR and this should not be larger than 1/8
>second for effective shaping to occur. So in the example listed above, TC =
>8K/64K = 1/8 second. So this is what the router would do for each TC.
>
>8000(Bc+Be), 8000(Bc), 8000, 8000, 8000, 8000, 8000, 8000
>
>And this would equal 64k.
>
>If the port speed was 128KB but you configured the Be = 64000, then this is
>what you would see:
>
>72000, 8000, 8000, 8000, 8000, 8000, 8000, 8000
>
>
>-Joe
>
>-----Original Message-----
>From: Jim Brown [mailto:Jim.Brown@CaseLogic.com]
>Sent: Monday, January 07, 2002 4:35 PM
>To: 'omar guarisco'; ccielab@groupstudy.com
>Subject: RE: FRTS ...CIR vs. MinCIR command
>
>
>The way I understand it is the burstable port speed equates to CIR and the
>minCIR is actually the guaranteed CIR limit from the provider. When
>shaping,
>a congestion notification will throttle the bandwidth back to the minCIR
>value.
>
>
>-----Original Message-----
>From: omar guarisco [mailto:oguarisco44@hotmail.com]
>Sent: Monday, January 07, 2002 3:11 PM
>To: ccielab@groupstudy.com
>Subject: FRTS ...CIR vs. MinCIR command
>
>
>With FRTS what is the difference configuring the CIR versus configuring the
>minCIR ???
>
>If I buy a Service from Provider which states that the PVC between Main
>Site
>
>A and Branch office B the CIR is 64 Kbit/s....I would configure on FRTS the
>CIR as 64....but what about MinCIR ???
>
>Tnx for the help
>Omar
>
>
>
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