From owner-freebsd-hackers Tue Jan 31 13:04:15 1995 Return-Path: hackers-owner Received: (from root@localhost) by freefall.cdrom.com (8.6.9/8.6.6) id NAA28817 for hackers-outgoing; Tue, 31 Jan 1995 13:04:15 -0800 Received: from cs.weber.edu (cs.weber.edu [137.190.16.16]) by freefall.cdrom.com (8.6.9/8.6.6) with SMTP id NAA28806 for ; Tue, 31 Jan 1995 13:04:11 -0800 Received: by cs.weber.edu (4.1/SMI-4.1.1) id AA28146; Tue, 31 Jan 95 13:29:59 MST From: terry@cs.weber.edu (Terry Lambert) Message-Id: <9501312029.AA28146@cs.weber.edu> Subject: Re: sys/netipx -Reply To: supervisor@alb.asctmd.com Date: Tue, 31 Jan 95 13:29:58 MST Cc: freebsd-hackers@FreeBSD.org In-Reply-To: from "supervisor@alb.asctmd.com" at Jan 30, 95 01:44:19 pm X-Mailer: ELM [version 2.4dev PL52] Sender: hackers-owner@FreeBSD.org Precedence: bulk > Would it make sense to create protocol family callbacks which would be > available to the ethernet hardware drivers? Is there such an interface > already defined? Yes and no. Callbacks probably mean that you are screwing up load order more than nything else -- that is, breaking the layering model or otherwise blurring the distinction between the logical layering. The "yes" part is that protocols like IPX benefit greatly by peeking into the packet to know the size before the allocate which cuts the number of copies by one and (potentially) allows a packet unload directly into the user buffer. NetWare uses this internally and has 1/4 the latency in it's stack of the IPX code in many UNIX implementations ("many" and not "all" because there are several implementations that have much, much worse latency). This is very important for request/response architectures, such as SMB (LANMAN) and NCP (NetWare). The cost on top of the layering abstraction getting less clean is that you must have outstanding posted reads to receive a packet, which means pre-dedicating buffers and other rather uncouth things. Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.