The arguments behind my choice here is cost driven, the 64kbps line is a fixed monthly rate for unlimited use, the 512kbps line costs us roughly ZAR250 per 3GB of usage. This can get quite expensive as the lines in question is for a college and we all know what students do to bandwidth :)
Taken the amount we pay every month for the 64kbps line it's more economical to over utilize the link as a primary connection than to have it lying around as a backup. South Africa and data connections don't go well in the same sentence...
As Chris suggested, I need something that can detect when Link A is saturated and then redirect the traffic over Link B until there is available bandwidth on Link A again. The rate limit trick of Taylor might work once I get to understand the usage patterns of these students. But for at least the first 3 months I won't have proper data at my disposal.
Thanks for your replies!
On 4/24/05, Chris Bennett <chris@xxxxxxxxxx> wrote:
You can't split a particular IP connection between two links, but can instead only determine which link a particular connection will occur on. Given this, it sounds like you want to have some way to detect that Link A is already saturated and then send all further connections to Link B until Link A is no longer saturated.Maybe someone can tell you how to do that if that's really what you want to do (others here know far more about this than me), but my guess is you really don't want to do that. With the huge bandwidth disparity between the two links, route cacheing, and the inability know how much bandwidth any particular conneciton will consume, I think you'd end up with a giant mess... those people with connections unlucky enough to end up on Link A would probably be very unhappy people indeed.Generally speaking I think it would make more sense to put all traffic over Link B, and then use Link A only for emergencies. Maybe route the most critical traffic over Link A if you really want to feel like its being utilized as something other than a pure backup, but personally I wouldn't even do that.Just because Link A is more reliable and more expensive doesn't mean it makes sense to use it as your primary conduit. With Link B having eight times the bandwidth, it seems the obvious choice as the primary. Use it, and keep the users happy most of the time (instead of making them miserable most of the time). On the rare ocassions it goes down, use bandwidth shaping to make sure the highest priority traffic gets access to Link A first.In all the time I've used DSL, I've had severe outages twice for reasons other than standard maintenance. In both cases (in two separate locations), the cause was the ILEC phone company mistakingly dropping the wire pair while doing other work (freakin took over a week in each case to get my connectivity back!!). This sort of thing could just as easily happen with a leased line though, so I'm not really sure I buy that the leased line is really more reliable than DSL line from a high quality ISP. Although maybe a particular SLA makes it so in some legal sense since you can then sue someone. Personally, if your leased line really costs more than the DSL, I'd get rid of it and get a 2nd DSL line from another provider and use that as your backup instead.Anyway, I guess my main point is that the high cost of your leased line might be clouding your thinking on this. I wouldn't let the comparitive cost be your guiding light here. Go with what makes sense from a technology perspective, and don't guilt yourself into trying to get full utilization out of the slow link just because it costs more.----- Original Message -----From: Kenneth KalmerTo: lartcSent: Saturday, April 23, 2005 4:34 PMSubject: Spill overList
I need some help, advice or just a starting point on the following situation:
Link A - 64kbps leased line
Link B - 512kbps ADSL line
Is it possible to have Link A saturated constantly and have the excess traffic "spill over" onto Link B? I know it's possible to have packets sent down links in a round-robin fashion and I've read in the howto on load sharing over multiple interfaces (http://lartc.org/howto/lartc.loadshare.html ), but I do not have control over the termination of the link at the ISP's (two different one as well). Also note that splitting different protocols over each of these links are not possible in our case.
Reason being, Link A is a more reliable and more expensive link, so I need to over-use it's capacity if it we're, and use the cheaper ADSL (link B) offering to keep al services running when the leased line (A) is saturated.
Any tips, suggestions and comments would be welcomed.
Regards
--
Kenneth Kalmer
kenneth.kalmer@xxxxxxxxx
http://opensourcery.blogspot.com
_______________________________________________
LARTC mailing list
LARTC@xxxxxxxxxxxxxxx
http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
_______________________________________________
LARTC mailing list
LARTC@xxxxxxxxxxxxxxx
http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
--
Kenneth Kalmer
kenneth.kalmer@xxxxxxxxx
http://opensourcery.blogspot.com
_______________________________________________ LARTC mailing list LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
