--- Doug Veldhuisen wrote: >I am guessing since we are using Qos policies on these routers, I'm >seeing QoS drops, but not sure.
--- Christopher Sweeney wrote: It's ifOutDiscards in the ifTable. In theory, I think, the discards should indicate packets discarded because of things like resource limitations. In practice, we have seen some SNMP implementations which count other types of discards, such as discards due to firewall rules, in this number. --- end of quote --- Yes, I have heard that some equipment may discard packets for "good reasons" yet count them in the MIB-II statistic ifOutDiscards. This could make you think that there's a problem, even though there isn't. Here are some examples: - As Doug Veldhuisen notes above, a router may drop a packet that's otherwise OK because of a QoS policy. For example, if a stream of higher priority packets needs to be transmitted, the router may drop the lower priority ones. These packets could appear as discarded packets in MIB-II statistics. - A firewall may also choose to count firewalled packets as drops. This is an explicit policy decision, not a lack of buffer space, but still might be counted as a MIB-II discard. - Spanning Tree. Switches can (by design) ignore spanning tree updates, because they are not interesting or because spanning tree has been shut off. Certain brands of switches can count these as MIB-II discards. - Committed Information Rate. With permanent virtual circuits and similar technologies, normal behavior of a customer device may be to attempt to send data faster than the Committed Information Rate they have contracted for. The router will drop those packets, and the drops may be counted in the SNMP MIB-II stats. Any comments from the list on these or other situations? Thanks! Rich Brown [EMAIL PROTECTED] Dartware, LLC http://www.dartware.com 10 Buck Road, PO Box 130 Telephone: 603-643-9600 Hanover, NH 03755-0130 USA Fax: 603-643-2289 ____________________________________________________________________ List archives: http://www.mail-archive.com/intermapper-talk%40list.dartware.com/ To unsubscribe: send email to: [EMAIL PROTECTED]
