Date: Mon, 1 Feb 1999 07:12:40 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: wes@softweyr.com (Wes Peters) Cc: yu.shi@research.nokia.com, freebsd-net@FreeBSD.ORG Subject: Re: drop packets? Message-ID: <199902010612.HAA20000@labinfo.iet.unipi.it> In-Reply-To: <36B55034.C6332745@softweyr.com> from "Wes Peters" at Jan 31, 99 11:56:33 pm
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> > If the IF output queue is often full, why ip stack does not get feedback > > from the driver and buffer the packets so that less packets are dropped > > ? > > The IP stack does buffer packets, in the output queue. It gets feedback ... > IP packets are queued in data structures known as mbufs. The default > number of mbufs in your system is controlled by the "maxusers" option > in your config file. The default number of mbuf clusters, ... just a clarification: the queue logically belongs to the "if" layer, not IP (not that you are saying this, but your sentence above is ambiguous). The size of the interface queue is by default 50 pkts for Ethernet cards (10/100 makes no difference), and fewer for other interfaces. Unless you have lots of interfaces and local servers is unlikely that the forwarding process consumes many MBUFS, at 50 per interface. There are other reasons why you can run out of mbufs e.g. by using a lot of local TCP servers (then you do buffer pkts in the TCP queues), or if you have a leak in your ethernet driver (some used to have) or finally if you use dummynet with a lot of oddly-configured pipes. cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO . EMAIL: luigi@iet.unipi.it . Dip. di Ing. dell'Informazione HTTP://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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