[kwlug-disc] Bandwidth aggregation

unsolicited 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 
bits.



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