was CEF and per packet load sharing [7:72258]
Consider two routers which have 3 GEs between them (no L2 device between them). Is it better to configure each of these GEs as a standalone L3 connection or to combine them GEs into an etherchannel (802.1ae?) bundle? My $0.02 would be to keep them at L3 and not run another protocol underneath to enable bundling. The question I've heard with this approach is how granular the load splitting works when splitting load across three interfaces. If CEF does per packet load splitting, would the load be (nearly) equal across the three interfaces (eg within 1-2% at all times)? When using per packet CEF, is there an issue with packets being received out of order? (Consider some flow where a large packet is sent over one interface and the following flow packet is small and sent over another interface. The small packet might be received completely before the large packet. Does per packet CEF address this issue?) I had heard that etherchannel (or the IEEE derivative) would support nearly equal load splitting across N interfaces. And it also defines a mechanism so that the receiving router would be able to detect and re-order packets which arrive out of order). Comments? Pointers to relevant docs? THanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=72258t=72258 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: was CEF and per packet load sharing [7:72258]
We use CEF quite a bit, over 200 remote nodes with multiple circuits, it works out very well for us. The load on the circuits is always very close, I couldn't tell you with any certainty that it is within 1 to 2 percent though. I have had 2 issues with CEF in the past 2 years, and both involved FTP applications from certain vendors. It seems that every now and then I run across an FTP application that doesn't work correctly with CEF, the issue was that you would only get one quarter of the available bandwidth when using CEF, but as soon as you use multilink the issue goes away, I don't know what it is and it has never been worth the time to find out. All in all I am very happy with CEF using per-packet load sharing and I would recommend it over multilink any day (personal preference, I am not saying that people who use multilink are bad). I can't say anything in defense of or against etherchannel because I have only used it in the lab. -Original Message- From: p b [mailto:[EMAIL PROTECTED] Sent: Monday, July 14, 2003 2:18 PM To: [EMAIL PROTECTED] Subject: was CEF and per packet load sharing [7:72258] Consider two routers which have 3 GEs between them (no L2 device between them). Is it better to configure each of these GEs as a standalone L3 connection or to combine them GEs into an etherchannel (802.1ae?) bundle? My $0.02 would be to keep them at L3 and not run another protocol underneath to enable bundling. The question I've heard with this approach is how granular the load splitting works when splitting load across three interfaces. If CEF does per packet load splitting, would the load be (nearly) equal across the three interfaces (eg within 1-2% at all times)? When using per packet CEF, is there an issue with packets being received out of order? (Consider some flow where a large packet is sent over one interface and the following flow packet is small and sent over another interface. The small packet might be received completely before the large packet. Does per packet CEF address this issue?) I had heard that etherchannel (or the IEEE derivative) would support nearly equal load splitting across N interfaces. And it also defines a mechanism so that the receiving router would be able to detect and re-order packets which arrive out of order). Comments? Pointers to relevant docs? THanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=72259t=72258 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: was CEF and per packet load sharing [7:72258]
I had heard that etherchannel (or the IEEE derivative) would support nearly equal load splitting across N interfaces. And it also defines a mechanism so that the receiving router would be able to detect and re-order packets which arrive out of order). I've never heard of that. In fact, excerpts from the document link below state the algorithm is deterministic; given the same addresses and session information, you always hash to the same port in the channel, preventing out-of-order packet delivery. You could always read this doc: http://www.cisco.com/en/US/partner/tech/tk389/tk213/technologies_tech_note09 186a0080094714.shtml Which is Understanding EtherChannel Load Balancing and Redundancy on Catalyst Switches Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: p b [mailto:[EMAIL PROTECTED] Sent: Monday, July 14, 2003 2:18 PM To: [EMAIL PROTECTED] Subject: was CEF and per packet load sharing [7:72258] Consider two routers which have 3 GEs between them (no L2 device between them). Is it better to configure each of these GEs as a standalone L3 connection or to combine them GEs into an etherchannel (802.1ae?) bundle? My $0.02 would be to keep them at L3 and not run another protocol underneath to enable bundling. The question I've heard with this approach is how granular the load splitting works when splitting load across three interfaces. If CEF does per packet load splitting, would the load be (nearly) equal across the three interfaces (eg within 1-2% at all times)? When using per packet CEF, is there an issue with packets being received out of order? (Consider some flow where a large packet is sent over one interface and the following flow packet is small and sent over another interface. The small packet might be received completely before the large packet. Does per packet CEF address this issue?) I had heard that etherchannel (or the IEEE derivative) would support nearly equal load splitting across N interfaces. And it also defines a mechanism so that the receiving router would be able to detect and re-order packets which arrive out of order). Comments? Pointers to relevant docs? THanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=72264t=72258 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: was CEF and per packet load sharing [7:72258]
At 06:18 PM 7/14/2003 +, p b wrote: Consider two routers which have 3 GEs between them (no L2 device between them). Is it better to configure each of these GEs as a standalone L3 connection or to combine them GEs into an etherchannel (802.1ae?) bundle? My $0.02 would be to keep them at L3 and not run another protocol underneath to enable bundling. Bundling is useful to decrease L3 complexity (less IP addresses, less links, less instability in routing). The question I've heard with this approach is how granular the load splitting works when splitting load across three interfaces. I think the Cisco implementation splits based on flow (not quite sure what flow exactly means in this context but it is not that important), so the load might be split unevenly. If CEF does per packet load splitting, would the load be (nearly) equal across the three interfaces (eg within 1-2% at all times)? Should be. Unless you construct traffic specifically to screw it up, like send 2 64 byte packets, then a 1500 byte packet, and then repeat... :) When using per packet CEF, is there an issue with packets being received out of order? Yes. (Consider some flow where a large packet is sent over one interface and the following flow packet is small and sent over another interface. The small packet might be received completely before the large packet. Does per packet CEF address this issue?) No. How could it? CEF is a decision making mechanism local to the router, not an encapsulation. Thanks, Zsombor I had heard that etherchannel (or the IEEE derivative) would support nearly equal load splitting across N interfaces. And it also defines a mechanism so that the receiving router would be able to detect and re-order packets which arrive out of order). Comments? Pointers to relevant docs? THanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=72273t=72258 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
