Date: Mon, 30 Aug 2004 09:06:29 -0700 (PDT) From: Richard Hodges <rh@matriplex.com> To: Ted Mittelstaedt <tedm@toybox.placo.com> Cc: freebsd-atm@freebsd.org Subject: Re: Question on ATM w/ FreeBSD Message-ID: <20040830083817.G46053@mail.cheapline.net> In-Reply-To: <LOBBIFDAGNMAMLGJJCKNOEDIEPAA.tedm@toybox.placo.com> References: <LOBBIFDAGNMAMLGJJCKNOEDIEPAA.tedm@toybox.placo.com>
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On Mon, 30 Aug 2004, Ted Mittelstaedt wrote: > Hi All, > > Can I plug in an ATM DS3 into something like a Cisco Lightstream LS1010 > with a DS3 card, then plug a PC running FreeBSD and Quagga, with a > Marconi Forerunner HE155 using the fatm() driver, into a OC3 card on > the LS1010, then define a VC, switch it through the switch, > and run data over that? I cannot answer for netgraph-atm (maybe Harti could help there), but I have some knowlege about the Fore/IDT LE155 card and HARP/ATM in the later versions of 4.x HARP supports RFC1483 routed packet encapsulation, and if your other end supports this, then you should be fine. Many or most ATM/Ether switches prefer 1483 bridged encapsulation, so this is an important thing to check. LANE (LAN emulation) uses bridged, CLIP (classical IP) uses routed encapsulation, by the way. The LS1010 or any decent ATM switch should be fine to link your DS3 to OC3. For the price, I would go for a Fore ASX-200BX or an ASX-200WG converted to a -BX (by upgrading the CPU board). The -WG is usually very cheap on ebay. > We are looking into bringing in another feed this time via ATM DS3, > and I don't think that a DS3 ATM card exists for the PC that has a > FreeBSD (or Linux) driver. I think Imagestream sells one, but I would rather spend a couple hundred on an ATM switch than a thousand or more on a PCI card. > However I see a number of PCI ATM lan adapters for PC's. The Fore/IDT LE155 cards are cheap and functional. > It seems that an ATM switch, of which there are plenty > available, would be the way to get from one to the other. However I > have not dealt yet with ATM switches, is there anything inherently different > about ATM on a lan adapter like the HE155, and ATM on a DS3? Not really. Obviously the cell rate is different. This _might_ be an issue if your host with the OC3 bursts packets to the point that your DS3 bandwidth is exhausted and packets are discarded. By the way, if you have an option for EPD (early packet discard), this can help reduce the damage in this case. One ugly way to fix this would be to hack the IDT driver to force a lower cell rate. On the other hand, if your traffic is TCP, flow control might not be an issue. I think the key is making sure that the other end can handle RFC1483 routed encapsulation. You should have no trouble finding the LE155 card, the switch, and the OC3 and DS3 modules on ebay, but feel free to contact me for parts if you wish. All the best, -Richard
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