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Re: [PLUG] doubling bandwidth and achieving network redundancy
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Hi Son To,
If you want to switch your Bell ADSL from BellAtlantic.net to DCANet
and so lose the requirement to have PPPoE support, please call us
at 800-784-4788 and talk to Valerie Vasser at extension 123. Just
tell her that you have BellAtlantic DSL and want to do an "ISP switch".
-Andrew White
awhite@dca.net
On Tue, 22 Aug 2000, William H. Magill wrote:
> > Date: Fri, 18 Aug 2000 12:02:23 -0400
> > From: Stephen Brown <steve@dataclarity.net>
> >
> > Son To wrote:
> > >
> > > I do not know much about routers so can someone tell me if it is possible
> > > to achieve this using a Linux router.
> > >
> > > My bellatlantic ADSL is unreliable. It would work great for a week or so
> > > then disconnects me. I have to restart pppoet.
> > >
> > > Suppose I get two ADSL line from two different ISP, can a Linux router
> > > be configured so that traffic is load balance between the two lines? A TCP
> > > data stream is sent/recieve using both lines. If one line goes down, my
> > > internal network should not notices the broken connection.
> >
> > Yes, but it isn't as easy as it should be. The linux end of things
> > will be trivial compared to the hassles in the real world.
> >
> > You have 2 basic options:
> > The easiest is to get redundant connections from a single provider
> > which may allow you to do link trunking across the 2 links, and keep
> > a single IP block.
> >
> > The other one is what most ISPs and colo facilities do, but on a smaller
> > scale. It will require you to get an ASN (Autonomous System Number) from
> > ARIN (http://www.arin.net/), run BGP4 on the Linux router and either get
> > a block of 'transportable' IP addresses from ARIN, or IP addresses from
> > one ISP that are advertised to the rest of the Internet so you can reach
> > your IPs through either upstream connection. The other drawback is that
> > for a single TCP connection you really won't get a doubling in bandwidth
> > because the routers in the core of the net will point all traffic to the
> > closest ISP instead of sending half to one and half to the other.
> >
> This sounds good, but in reality it is seriously non-trivial.
>
> On a good day, (all) the Internet Backbone providers can get this to work.
> However, on a bad day -- which is when you need it -- it doesn't work,
> period, somebody has to intervene manually, 9 failures out of 10.
>
> Penn keeps going back to this well every 6 months or so, but we sill come up
> empty. It all works in theory, but when one line fails, somebody always has
> to go "tweak something," that wasn't configured right anymore because of
> some change that got made to the IOS or routing tables or... "last week."
> The rate-of-change factor here is just deadly.
>
> It's not that it can't work, it's just that it doesn't. Something always
> changes between the two times when you need it to work.
>
> Link trunking only works when the routers at both ends are going to the
> same places and know about each other. (And you do need a router at both
> ends, in addition to the xDSL modem.) Across two different ISPs, forget
> about it. It will give you the redundancy AND bandwidth increase if you
> use say a Cisco router on both ends, much the same way 128K ISDN line
> "doubles up." I don't know if any xDSL ISP is sufficiently sophisticated
> enough in the sales end to have a clue about what you want to do, and
> therefore how to answer your query. The techs, especially if they work with
> Cisco gear are familiar with it. (Cisco is the one who pioneered using two
> say 56K lines to equal one 128K line. It's really kind of neat how it just
> works when you have the matching equipment and configurations.)
>
> By the time you move up the food chain from "residential" to "commercial"
> sales, they are used to working with multiple lines and line types, but the
> prices go up accordingly.
>
> However, unless I am very mistaken, your problem has to do not with xDSL
> reliability but with PPPoE. I've had BA Infospeed since January, and aside
> from the great ATM cloud problem in the winter, have not seen a single
> outage.... but then I have static addresses from my ISP, DCAnet, and even
> if the link did drop, I'd never know it. Unlike PPPoE, I don't have to
> have a daemon running locally to have connectivity.
>
> So before you blame your Bell Atlantic Infospeed xDSL connection, consider
> getting a different ISP and loose PPPoE. I don't know how easy that is now
> that Verizon exists -- and they dropped all references to any ISP except BA
> from their web site... and since Verizon got out of the xDSL business last
> month. Call DCA (or visit their web site) and ask them to get you switched
> over. Don't forget that not much will happen until after the strike is over.
>
> One last point -- "Perfect connectivity" (24x7) is NOT what xDSL, or even
> Cable Modems are about. Both are simply "best effort" services. Even on the
> backbone, nobody gives you service guarantees unless you pay big bucks for
> them. And even then, the contracts have more weasel words in them than
> Bill Clinton ever heard of! Because of its pricing xDSL is seriously on the
> low end of the totem pole when it comes to "service."
> To get more of an idea what I'm talking about, check out:
> http://www.dslreports.com/shownews/125
>
>
______________________________________________________________________
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