Priscilla and the rest of the group, Thanks for your reply.
No, I don't want to prioritize ICMP, my mistake, only telnet traffic. More questions though. 1. Do I have to add the "priority-list 1 protocol ip high tcp telnet" on both sides of the link as the telnet connection will go through the Internet. I am at this stage not sure on which side the bottle neck is? 2. Will creating a tunnel (interface Tunnel0) maybe improve performance if I change the routing for the destination address to go via the tunnel? Regards Johan -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: 21 January 2003 22:08 To: [EMAIL PROTECTED] Subject: Re: ICMP Traffic [7:61453] Captian Lance wrote: > > You can use queuing to accomplish priority by protocol, however > ICMP and > Telnet are two different protocols. Telnet, an application > layer protocol, > does not use ICMP. ICMP, a network layer protocol, is used for > message > delivery, such as Echo requests and echo replies (PING). If > you need > additional help please send me an email. Please keep the conversations on the list so we all learn from them! Thanks. :-) If you're worried that the conversation would be too basic for the group, I would say in most cases, that's not true. There's no such thing as a dumb question (or answer) on a study group, IMHO, and lots of people need more info on protocol behavior, since Cisco doesn't focus on that enough in their learning materials. Telnet is indeed an application-layer protocol that runs above TCP and IP. It's interactive and uses very short packets, with each character you type in a single packet usually. The server side may send bigger packets when it sends prompts (or screens with TN3270), but the packets are still pretty small. With something like weighted-fair queuing (WFQ), Telnet would be automatically prioritized, since short-packet flows are prioritized automatically with WFQ. WFQ is on by default on serial links with a speed of about 2 Mbps or less. If that doesn't help or doesn't apply to your situation, then the easiest solution for prioritizing Telnet would be priority queuing. The config would be something like: priority-list 1 protocol ip high tcp telnet int s0 priority-group 1 This applies to traffic forwarded by the router, not to traffic sent by the router. If your goal is to priorize Telnet access to or from the router, I don't think you have to do anything. It's pretty well prioritized anyway, as far as I know. Now, for ICMP. You could prioritize it also, although I would wonder why you would want to do this. I think it would be a mistake, since ICMP is used for pings. You could end up prioritizing a ping scan, for example. And, in this case, if you are trying to prioritize packets sent by the router, it probably won't work. ICMP is purposely not prioritized by routers. But if you want to prioritize ICMP packets forwarded by the router, you could do priority queuing with: priority-list 1 protocol ip high tcp icmp int s0 priority-group 1 One last caveat, though. ICMP is generally sent by the router, not forwarded by the router. With the exception of ping (echo), ICMP's main job is for a router to send back status and error messages. The formatting for the following table from my book may get screwed up, but I think you'll get the flavor of it. It lists the ICMP message types to give you an idea of what ICMP is good for: ICMP Types and Codes Type Code Meaning 0 0 Echo reply (ping reply) 3 x Destination unreachable (generic category) 3 0 Network unreachable 3 1 Host unreachable 3 2 Protocol unreachable 3 3 Port unreachable 3 4 Fragmentation was needed and the don't fragment (DF) bit was set 3 5 Source route failed 3 13 Packet administratively prohibited 4 0 Source quench* 5 x Redirect (generic category) 5 0 Redirect datagrams for the network 5 1 Redirect datagrams for the host 5 2 Redirect datagrams for the type of service and network 5 3 Redirect datagrams for the type of service and the host 8 0 Echo (ping) 11 x Time exceeded (generic category) 11 0 Time-to-live (TTL) exceeded 11 1 Fragment reassembly time exceeded 12 0 Parameter problem * Per RFC 1812, a router should not originate source quench messages. A host may send source quench messages, however, per RFC 1122. Hope that helps! Send us another question once you figure out what you really want to do. Thanks. _______________________________ Priscilla Oppenheimer www.troubleshootingnetworks.com www.priscilla.com > > Lance > > ""Johan Bornman"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > How do I prioritize ICMP (Telnet) traffic on a 1601, no > routing protocol > > involved. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61543&t=61453 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
