not sure there is an absolute answer as it would depend on actual cable distance travelled (not as the crow flies), number of hops, policies enforced, congestion, etc. as a rule of thumb i would use estimated distance in kilometers / (400kilometers per second * .6). it is usually in the ballpark. if you are an order of magnitude higher it would indicate a problem.
thanks. ----- Original Message ----- From: "Symon Thurlow" To: Sent: Saturday, November 23, 2002 8:33 AM Subject: RE: bandwidth vs. latency [7:57899] > Anyone know what the average expected latency over Frame Relay is? > > -----Original Message----- > From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] > Sent: 23 November 2002 01:24 > To: [EMAIL PROTECTED] > Subject: RE: bandwidth vs. latency [7:57899] > > > Mirza, Timur wrote: > > > > does anyone have a good reference (e.g., white paper) on the nature of > > bandwidth vs latency & the distinction bet/ the two? > > Well, the distinction is easy. They don't mean the same thing at all. A > good site is Merriam Webster's online dictionary. The 2nd definition for > bandwidth is: > > Bandwidth: the capacity for data transfer of an electronic > communications system > > Latency, on the other hand, means delay. Websters isn't too helpful in > this case, but might help you understand the origin of the word, which > is related to dormancy. > > Cisco's Terms and Acronyms document has a couple definitions of latency, > which are somewhat helpful: > > 1. Delay between the time a device requests access to a network and the > time it is granted permission to transmit. > > 2. Delay between the time a device receives a frame and the time that > frame is forwarded out the destination port. > > Those definitions allude to the many contributors to delay (latency) on > a > network: > > * media access time > * queuing time at internetworking devices > * processing time at internetworking devices and at the sender and > receiver > * serialization delay to send and receive bits at the rate specified by > the bandwidth of the sending and receiving interfaces > * propagation delay which is distance dependent and to a certain extent > medium dependent, although most media support about 2/3 the speed of > light > > Testing latency is reasonably easy. Just do some pings. Predicting, > modeling, and simulating delay is advanced engineering. A few books > cover it at a very basic level, including Top-Down Network Design by > Oppenheimer, and Data Network Design by Spohn. > > Howard Berkowitz has written some RFCs that discuss performance > measurement, if I recall. > > There are graduate level computer science classes that cover performance > measurement in computer networks at many universities. > > And, finally, you can get some info from white papers written by vendors > who sell modelling software. For example, try http://www.netpredict.com/ > and http://www.opnet.com/. > > _______________________________ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > > > Timur Mirza > > Principal Network Engineer > > Network Planning & Engineering, West Region > > 15505-B Sand Canyon Avenue > > Irvine, California 92618 > > Verizon Wireless > > 949.286.6623 (o) > > 949.697.7964 (c) > ============================================= > > This email has been content filtered and > subject to spam filtering. If you consider > this email is unsolicited please forward > the email to [EMAIL PROTECTED] and > request that the sender's domain be > blocked from sending any further emails. > > ============================================= Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=57939&t=57899 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
