Date: Thu, 8 Oct 1998 13:47:35 -0700 (PDT) From: Tim Wolfe <tim@clipper.net> To: Bill Fumerola <billf@chc-chimes.com> Cc: "Jeffrey J. Mountin" <jeff-ml@mountin.net>, freebsd-isp@FreeBSD.ORG Subject: Re: IP Load balancing Message-ID: <Pine.LNX.4.02.9810081330430.778-100000@mailhost.clipper.net> In-Reply-To: <Pine.HPP.3.96.981008105105.21428D-100000@hp9000.chc-chimes.com>
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On Thu, 8 Oct 1998, Bill Fumerola wrote: > Agreed, I'm quite willing to accept the many reasons why a switch is > better then a hub, and I can't find a single reason why a level 3 switch > has anything more then level 2, short of a higher price tag. Keep in mind that I'm not even a self proclaimed expert here. This is my admittedly limited understanding of the layer2/layer3 switching issue. Layer2 Switching Hub: Listens to and remembers every MAC address (upto that switches capacity, usually somewhere between 4K and 64K addresses) seen on a given port and intelligently switches traffic destined to a remembered address to the correct port and only to that port. You have no option to change which port traffic for a given machine is sent to except by moving that device to a different port or ethernet segment. Layer3 Switching Hub: Listens to things at a protocol level, basing it's switching decisions on the (in this case) IP address rather than the MAC address. This gives an administrator the ability to setup routing (or forced switching of traffic to specific destinations via specific ports) for traffic that might be multiple hops away based on things other than just next hop. This would be useful for load balancing links to servers (just to show a single practicle application) Ie: A+++B===C Where A is a router connected to the internet (since this is fantasy anyway, let's say it is connected via multiple OC3's) B is a layer3 Routing switch (connected to A via gigabit ethernet) C is a web server with the most popular website in the world! (connected to B via 2 100MB ethernet links) B has 2 equal cost routes to C and load balances all traffic to the same. Now this particular instance I spent about 5 minutes thinking of so I know there are tons of holes and/or better ways to do this. The point is, at Layer3, you get a measure of control over network flow and traffic structure.. Tim ---------------------------------------------------- Timothy M. Wolfe | Why surf when you can Sail? tim@clipper.net | Join Oregon's Premier Sr. Network Engineer | Wireless Internet Provider! ClipperNet Corporation | http://www.clipper.net/ ---------------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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