cool thanks for the info! -- RFC 1149 Compliant.
""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > At 01:56 PM 2/15/02, Steven A. Ridder wrote: > >Are you saying that the fact the router's routing process that sent the > >packet to be forwarded considers the packet "gone" even though it's still in > >output queue's buffer being transmitted? > > Yes. That would be good router architecture. A paper I found on CEF has > some nice drawings of router "modules." See that the IP Input Process that > does the forwarding is separate from the Output Interface Processor in the > drawing here: > > http://www.cisco.com/warp/public/105/20.html > > This discussion does point out an interesting thing about TTL. It never > really was a time to live on the internetwork, because it didn't take > either serialization or propagation delay into account. It just took router > processing delay into account. I think that's because the router processing > time was an issue back in the 70s and 80s. > > Serialization delay also contributed to overall delay, of course, but > wasn't as big an issue as processing delay. (I think the original ARPANET > was built on 9600 bps lines.) Propagation delay hasn't changed much over > the years and isn't a big contributor compared to the others, (depending on > distance). Bits still traveled at approximately 2/3rds the speed of light > back then just like they do now. > > But the Honeywell Interface Message Processors (IMPs) that acted as routers > were the size of a refrigerator, buggy, sluggish, and hard to program. I > don't know MIPs or MHz, but we're talking SLOW. ;-) > > Priscilla > > > > >-- > >RFC 1149 Compliant. > > > > > >""Priscilla Oppenheimer"" wrote in message > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > At 01:25 PM 2/15/02, Hire, Ejay wrote: > > > >I lab-ed this, and did not observe the TTL incrementing even when the > >delay > > > >was over 8,000 ms. (It's not how fast you send the packets, but how > slow > > > >you make the link!) > > > > > > Hmm, that's an interesting approach, but I'm not sure it's a valid test. > > > Think about the layering and modularization of protocols and router > tasks. > > > IP forwarding doesn't know how long it takes to output bits. It couldn't > > > decrement the TTL based on the delay in sending, even if the TTL really > >did > > > still have a time-based meaning rather than a hop count meaning. > > > > > > Priscilla > > > > > > > > > > > > >-----Original Message----- > > > >From: Michael Williams [mailto:[EMAIL PROTECTED]] > > > >Sent: Friday, February 15, 2002 11:54 AM > > > >To: [EMAIL PROTECTED] > > > >Subject: RE: TTL and modern (fast) routers [7:35507] > > > > > > > > > > > >AFAIK, the TTL gets decremented by one by a router as it passes it on > (if > > > >it's held under one second), or by the number of seconds it was held if > >it > > > >is held over one second. I agree that anything more than 1000ms of > delay > > > >seems outrageous for a single hop these days, but I don't know of > >anything > > > >that has changed that "rule" that both you and I describe. > > > > > > > >Mike W. > > > ________________________ > > > > > > Priscilla Oppenheimer > > > http://www.priscilla.com > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35540&t=35507 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
