Yeah, try copying a 12 meg msfc .bin over a WAN link that has latency of 125ms. So I only get to send 8 packets per seccond each as 512 bytes. (1000ms/125ms = 8)
tftp at the application layer is the one who sends the acks. For some reason I can't do a a "copy flash ftp". I'm guessing because I don't have anonymous login allowed on my ftp? Does that sound right? Tim > -----Original Message----- > From: Chuck Larrieu [SMTP:[EMAIL PROTECTED]] > Sent: Tuesday, October 23, 2001 12:44 AM > To: [EMAIL PROTECTED] > Subject: Re: Slow wan link. TCP traffic "ok", UDP not okay. Please > help! [7:23853] > > validating this thought, I have had reason to upgrade my router pod IOS > images of late. Cisco's router Software Loader uses TFTP to copy new > images > into flash via a direct ehternet to ethernet connection. copying 16 meg > images takes an inordinate amount of time, especially considering there > are > only two devices on the network involved. > > it would appear, then, that the router writes each packet to flash before > requesting the next packet. at least that goes a long way towards > explaining > why the copies take several minutes on a 10baseT link with just the two > devices connected via a crossover cable. > > thanks for the insight > > Chuck > > > ""Priscilla Oppenheimer"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > One more (serious!) comment. I asked a protocol guru about the question > of > > TFTP being so slow. He agreed with the poster that the TFTP throughput > > seems awfully low, but he agreed with me too that TFTP is not optimized > for > > throughput. He also mentioned one other stupidity with TFTP > > implementations. He said that some actually write the 512-byte block of > > data to the hard disk before ACKing and asking for the next block. So a > > slow hard disk would cause problems. > > > > TFTP and UDP don't have a PSH bit like TCP has. With TCP, the sender > would > > output a bunch of data and then perhaps set the PSH bit which would tell > > TCP to give the data (in RAM) to the application. At that point, you > might > > see a short hiccup as FTP wrote the data to the hard drive (not > necessarily > > because FTP could still keep the data in memory until the session is > > closed; it's implementation-dependent.) > > > > TFTP is also implementation-dependent, but with some implementations, > it's > > one block at a time that is written to storage and then ACKed before > more > > data is sent. > > > > Since FTP works well, you have proof that the problem isn't with the > > network. Can't you pass this onto the server or application people!? ;-) > > > > Priscilla > > > > At 02:34 PM 10/18/01, Priscilla Oppenheimer wrote: > > >At 02:23 PM 10/18/01, Ouellette, Tim wrote: > > > >Priscilla, > > > > > > > > > > > > > >Thanks for the response. Any idea as to why the TFTP protcol over > our > > WAN > > > >will run at 4k/sec and FTP at 165k/sec. I just figured that the > smaller > > > >packet size of UDP would help. > > > > > >Nope. That would not help. It would make the throughput worse. > > > > > > > I also thought that UDP is connectionless and > > > >thefor requires no ACKS. > > > > > >TFTP has ACKs. > > > > > > > Other sites on our WAN I can transfer large files > > > >via TFTP and they run at very good speeds. > > > > > >Have you done the same sort of comparison of FTP versus TFTP at those > > >sites. I bet FTP has much better throughput. > > > > > > >I'm just concerned about this one > > > >site. Any other ideas? > > > > > >See the message from Phil Barker. It made some good points about TFTP > and > > >UDP in general not being tuned for WANs. The next step would be to put > a > > >Sniffer on it and see what's really happening. But there may not be > > >anything abnormal happening. TFTP just kinda sucks. > > > > > > > > > >Tim > > > > > > > > > > > > > -----Original Message----- > > > > > From: Priscilla Oppenheimer [SMTP:[EMAIL PROTECTED]] > > > > > Sent: Thursday, October 18, 2001 1:23 PM > > > > > To: [EMAIL PROTECTED] > > > > > Subject: Re: Slow wan link. TCP traffic "ok", UDP not okay. > Please > > > > > help! [7:23391] > > > > > > > > > > This list either filters my answers or mangles them. > > > > > > > > > > I'll make another try here. It it comes out mangled again, I'll > post > it > > > > > somewhere on my Web site when I have time. > > > > > > > > > > > > > > > TFTP is a trivial protocol running on top of a trivial protocol > (UDP). > > >You > > > > > > > > > > shouldn't expect it to have good throughput. > > > > > > > > > > TFTP uses a block size of 512 bytes. The protocol is a > command/reply > > > > > (Ping-Pong protocol) with no windowing, flow control, etc. The > protocol > > > > > looks like this: > > > > > > > > > > Write Request-> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > If there are any problems, the application-layer TFTP notices a > missing > > > > > ACK > > > > > and retransmits. > > > > > > > > > > FTP, on the hand uses TCP. It looks more like: > > > > > > > > > > SYN my segment (packet size) is 1500 > > > > > SYN ACK my segment size is also 1500 > > > > > ACK > > > > > > > > > > GET (FTP command), TCP receive window is 8,192 (or whatever)-> > > > > > > > > > > Hey All. I was wondering if someone could help me out with a > problem > > i'm > > > > > >working on. It's very weird to me and I can't find any reason why > this > > > > > may > > > > > >be happening other than possible a Queuing issue. Please comment. > > > > > > > > > > > > I've done some testing to show the response issues > from > > > > > spikinisse > > > > > >to an auburn hills tftp/ftp box. When a 9 meg > > > > > > file is copied from one of the 6509's in Spijkenisse > using > > tftp > > > > > we > > > > > >see a speed of 4k/sec (9041904 bytes copied in 2251.956 secs > (4016 > > > > > >bytes/sec) > > > > > > However, when I ftp'd a 2meg file from a server in > > Spijkenisse > > > > > to > > > > > >the same server in Auburn Hills, I see a speed of 166k/sec > (2024013 > > >bytes > > > > > >sent in 12 > > > > > > seconds (166.12 Kbytes/s) Seeing as in Spijkinisse it > is > > > > > >approximately 8pm and they have 4 E1's, there should not be an > issue > > >with > > > > > >over-utilization. > > > > > > It intrigue's me as to how a UDP based application > (tftp) > can > > > > > have > > > > > >such a ridiculously slow speed of 4k/sec and a TCP based > application > > > > > (ftp) > > > > > >has an > > > > > > average speed (considering 4 e1's) of 166k/sec. > > > > > > > > > > > > Spikinisse has a group of E1's to the cloud and our site > in > > > > > Auburn > > > > > >Hills has a full DS3 to the cloud. > > > > > > > > > > > >Spik is in the Netherlands, and Auburn Hills is in the US. Any > more > > > > > >information I need to provide? > > > > > ________________________ > > > > > > > > > > Priscilla Oppenheimer > > > > > http://www.priscilla.com > > >________________________ > > > > > >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=24006&t=24006 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
