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=57935&t=57899 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
