[kwlug-disc] Bandwidth aggregation
ldpaniak at fourpisolutions.com
Wed Feb 11 11:43:35 EST 2009
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Thanks for putting the time into a detailed explanation. I understand
now how my simple-minded picture of the issue was lacking.
Do you know how 'multi-link PPP' which appears to be available from the
ISP TekSavvvy compares to a "multihomed IP space"? Are these
operationally the same thing?
Andrew Kohlsmith (lists) wrote:
> On February 10, 2009 03:52:44 pm L.D. Paniak wrote:
>> 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?
> Yes it is. I said "multihomed IP space" -- that is not the same thing as two
> DSL or cable connections at all.
> Multihomed IP space means an IP address which is reachable through two or more
> providers. I'm not aware of any DSL, Cable, Cell or Wifi providers which give
> you this kind of address.
> If you get 220.127.116.11 from your DSL provider and 18.104.22.168 through your cable
> provider, both of those addresses are single-homed from your perspective. If
> someone on the internet sends a packet to 22.214.171.124, it will ONLY come from
> your DSL line, and never from your cable. If you send a request out your DSL
> connection, the response will come back through your DSL connection. It
> won't balance between the DSL and cable connections. You can try to fake
> your source address to have a request go out one and back the other, but any
> ISP worth their salt will be dropping packets not sourced from their own IP
> What I am doing is "extruding" multihomed IP space through a number of
> single-homed connections. Through SCS Internet, I have access to multihomed
> IP space. (e.g. 126.96.36.199/24.) Traffic to any of these addresses can come
> from one of (I think) three or four different providers into his rack.
> Using a server in that rack (with IP 188.8.131.52, for example), I "extrude" an
> IP, say 184.108.40.206. I use proxy-arp to as a means to capture traffic for that
> IP. Basically that means that whenever someone asks for the ethernet address
> of 220.127.116.11, the server responds with its own MAC.
> Your router at the office has a DSL and cable connection, with IP 18.104.22.168 and
> 22.214.171.124 from your respective providers. What I do now is to set up two GRE
> tunnels, one from 126.96.36.199 to 188.8.131.52 and one from 184.108.40.206 to 220.127.116.11. So
> now your home router actually has four routes: DSL-to-world, cable-to-world,
> DSL-to-server-via-tunnel0, cable-to-server-via-tunnel1.
> What I do now is to use iproute2 and iptables to set up a packet marking and
> load balancing system. I say that traffic for the world (i.e. default route)
> is via DSL-to-server-via-tunnel1 *AND* to cable-to-server-via-tunnel1, with
> equal weighting (neither route is preferred). I also to disable route
> caching, which works against us in this scenario. Now any traffic that the
> router wants to send out to the world will go through either tunnel and "pop
> out" as traffic from 18.104.22.168.
> It may have taken the path through the cable or DSL IP, but it was
> encapsulated in the tunnel at that point. The traffic exits from 151 Front
> with a source IP of 22.214.171.124 and heads out through any of the providers that
> he has available. It reaches the destination, and a response comes back to
> 126.96.36.199. The server receives that traffic, sends it back through one of the
> two tunnels, and your router gets it and does what it would normally do with
> it. All the tunnels are brought up and torn down with your standard ip-up
> style scripts that PPPoE gives, but you could also do it with the normal
> networking post-route scripts (for cable or wifi connections, for example).
> If a tunnel fails, the other tunnel's there, and traffic still flows. If you
> add more tunnels, the bandwidth is load-balanced over them. Since the
> 188.8.131.52 address is multihomed, you don't lose connectivity when one of the
> providers that SCS Internet uses has troubles, since that IP is reachable
> through several other paths. You can play with route metrics to favour one
> tunnel over the other, and of course you can play with the routing table
> selections on the router so that you do NOT use the multihomed space for
> regular web traffic, windows updates or whatever other nonessential traffic
> you may have.
> You can *also* use IPSec to encrypt everything over the tunnel.
> The only real downsides are
> 1) bandwidth considerations at the colo
> 2) slightly increased latency due to tunnelling and encryption
> I've used this method to provide highly-available bandwidth for the auto
> industry, where they were willing to pay for the colocated server at 151
> Front -- multihomed IP space was simply not available at some of their
> plants, and simply too expensive at others. They decided to get more bang for
> their buck by using the colocated server as an IPSec endpoint, FTP server for
> *huge* CAD drawings and a conferencing bridge instead of bringing absolutely
> all that traffic back to their home network.
> Anyway -- that's why I feel it's an esoteric topic. You can bring two DSL or
> cable connections together for home/office use, but that's not the same thing
> as what I described.
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