Brian, A few minutes after I sent my post I saw that coming. I was taking his statement "The burst size should 1/8 of the bit rate cfg'd" as a scenario requirement.
The "1/8" should have clued me into the fact the the problem was not stating a specific scenario requirement but just stating the Bc=CIR*Tc rule. Thanks, Jonathan > -----Original Message----- > From: Brian McGahan [mailto:[EMAIL PROTECTED] > Sent: Wednesday, June 18, 2003 2:53 PM > To: 'Jonathan V Hays'; 'John Smith'; [EMAIL PROTECTED]; > [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED]; > [EMAIL PROTECTED]; > [EMAIL PROTECTED]; 'CyscoExpert' > Subject: RE: QoS - Enabling Traffic Shaping > > > Jonathan, > > First let's make sure we're on the same page with definitions. > For traffic-shaping (both GTS and FRTS), the terms are as follows: > > AR = Access Rate (physical clock or rate-limit at local loop) > CIR = Average per second > Bc = Bits per interval committed > Be = Bits per interval excess > Tc = Interval in ms > > The following formula should be used to calculate Bc: > > Bc = CIR * Tc/1000 > > The following formula should be used to calculate Be: > > Be = (AR - CIR) * Tc/1000 > > > In this example, our access-rate is 64000bps. We are trying to > average 15% of our access rate for telnet traffic. Average per second > is CIR. > > CIR = 64000 bps X .15 = 9600 bps > > Let's assume for this example that our Tc is 1/8 second, or 125 > ms. Our committed burst size would then be as follows: > > Bc = CIR * Tc/1000 > Bc = 9600 * 125/1000 > Bc = 9600 * .125 > Bc = 1200 > > Now let's double check our calculation. > > We have 125 ms per interval. There are 1000 ms per second. > > 1 interval | 1000 ms > --------------------- = 8 intervals per second > 125 ms | 1 second > > If we are sending 1200 bits per interval 8 times per second: > > 1200 bits | 8 intervals > ------------------------ = 1200 * 8 = 9600bps > 1 interval | 1 second > > > As a side note, if you want no excess burst, you want the Be > value to be > zero, not the same as the Bc value. The syntax should then read as > follows: > > traffic-shape group 101 9600 1200 0 > > > > HTH > > Brian McGahan, CCIE #8593 > Director of Design and Implementation > [EMAIL PROTECTED] > > CyscoExpert Corporation > Internetwork Consulting & Training > Toll Free: 866.CyscoXP > Fax: 847.674.2625 > > > > -----Original Message----- > > From: Jonathan V Hays [mailto:[EMAIL PROTECTED] > > Sent: Wednesday, June 18, 2003 11:39 AM > > To: 'John Smith'; [EMAIL PROTECTED]; [EMAIL PROTECTED] > > Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; > > [EMAIL PROTECTED]; [EMAIL PROTECTED] > > Subject: RE: QoS - Enabling Traffic Shaping > > > > John, > > > > I assume the '25' after each percentage sign in your original post > below > > is a typo (e.g., "15%25 of bandwidth"). Given that assumption, you > want > > to assign traffic to three categories, with 15%, 50%, and 35% of the > 64 > > kbps bandwidth. > > > > 64000 x .15 = 9600 bps > > 64000 x .50 = 32000 bps > > 64000 x .35 = 22400 bps > > > > > burst size should 1/8 of the bit rate cfg'd, no excess burst > > > > 1/8 = .125 > > > > 9600 x .125 = 1200 bps > > 32000 x .125 = 4000 bps > > 22400 x .125 = 2800 bps > > > > However, I question the burst size given in your solution. The > > definition from the Doc CD states that the burst-size is the > "Sustained > > number of bits that can be sent per INTERVAL. On Frame Relay > interfaces, > > this is the Committed Burst size contracted with your service > provider. > > " > > > > See > > > http://www.cisco.com/univercd/cc/td/doc/product/software/ios12 > 2/122cgcr/ > > fqos_r/qrfcmd11.htm#1019905 > > > > If the interval is 1/8 second (and it may not be) I would think the > > correct answer would divide each of 1200, 4000, and 2800 by > 8, to get > > bits per interval. > > > > HTH, > > > > Jonathan > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > > > Behalf Of John Smith > > > Sent: Wednesday, June 18, 2003 10:21 AM > > > To: [EMAIL PROTECTED]; [EMAIL PROTECTED] > > > Cc: [EMAIL PROTECTED]; > > > [EMAIL PROTECTED]; [EMAIL PROTECTED]; > > > [EMAIL PROTECTED] > > > Subject: QoS - Enabling Traffic Shaping > > > > > > > > > Somehow I have forgotten how to do math... Can anyone explain > > > to me or point to a doc on figuring out the percentage for > > > the below lab. > > > > > > Enable traffic shaping on int serial 0/0 as follows: > > > > > > Shape Telnet and ICMP traffic to 15%25 of bandwidth > > > Shape FTP traffic to 50%25 of bw > > > Shape all remianing traffic to 35%25 of bw. > > > > > > Remember the total link bw is 64 kbps on this interface. The > > > burst size should 1/8 of the bit rate cfg'd, no excess burst > > > should be allowed. > > > > > > The answer from the lab help are, below can anyone tell me > > > how the number 9600, 32000 and 22400 were arrived at? I can > > > figure out the 1/8th part 1200, 4000 and 2800, but somehow > > > can't remember how to get the original percentage.. > > > > > > traffic-shape group 101 9600 1200 1200 > > > traffic-shape group 102 32000 4000 4000 > > > traffic-shape group 103 22400 2800 2800 > > > > > > Thanks. > > > > > > > > > > > > --------------------------------- > > > Do you Yahoo!? > > > SBC Yahoo! DSL - Now only $29.95 per month! > > > > > > > > > ______________________________________________________________ > > > _________ > > > You are subscribed to the GroupStudy.com CCIE R&S > Discussion Group. > > > > > > Subscription information may be found at: > > > http://www.groupstudy.com/list/CCIELab.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=70880&t=70880 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
