[kwlug-disc] Bandwidth aggregation
unsolicited at swiz.ca
Tue Feb 10 16:15:38 EST 2009
L.D. Paniak wrote, On 02/10/2009 3:52 PM:
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> I think it would be a great topic. WAN connections are easily the most
> unreliable part of a modern computer system. For things like VOIP,
> failover capability is essentially a requirement.
> Is it really that esoteric? Don't most homes/businesses have access to
> cable and DSL or two channels of DSL?
Esoteric, yes, in that you essentially have two choices:
(1) A single device must take in both 'providers', or each headend
device must run a gateway protocol. The devices have to negotiate
between themselves who's going to handle what. See (2). Ultimately,
only one device can have an IP. (DNS returns a single IP, essentially.
Fallbacks not included here.) Which device is going to claim the IP?
There is no guarantee as to the pathway of incoming packets - if one
device sends a packet out, expecting a reply, and it returns on the
other device, the other device goes "Why are you sending me this, I
didn't ask for it? Toss.) Such 'knowledgeable' devices are not overly
common at the consumer level.
(2) You have to maintain your own routing table. e.g. Your DNS IP
comes in and goes out one device. Your internal internet requests go
out the other. The advantages of, we'll call it 'load levelling' are
substantially lost. Good luck guessing which routes should go where.
Things get more complicated when services use reverse dns (smtp) to
verify the incoming packet is coming from the publicized source. And
the request went out the other.
That's what I can think of off the top of my head, but it gets
stranger and more irritating. e.g. Providers don't like them - it is
now up to you to make sure that their network can't be attacked via
your gateway from another provider. And they don't trust you. Let
alone, if the route gets into the routing table, they now have
multiple paths between providers. It gets stranger and stranger.
Thus the creation of gateway (edge) protocols to handle this nonsense,
and not many devices have that. Nonsense as it aggravation and fiddly
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