[kwlug-disc] Bandwidth aggregation
bjonkman at sobac.com
Wed Feb 11 11:50:34 EST 2009
And after teasing us like that, now we want to see pretty network
diagrams, sample config files, scripts, and maybe even a demo.
Yes, it's esoteric, and No, we promise not to try this at home, but
it's still interesting and presentation-worthy.
+1 for a presentation by Andrew!
-- -- -- --
Bob Jonkman <bjonkman at sobac.com> http://sobac.com/sobac/
SOBAC Microcomputer Services Voice: +1-519-669-0388
6 James Street, Elmira ON Canada N3B 1L5 Cel: +1-519-635-9413
Software --- Office & Business Automation --- Consulting
On 11 Feb 2009 at 9:59 Andrew Kohlsmith (lists) <kwlug-disc at kwlug.org>
about "Re: [kwlug-disc] Bandwidth aggregat[...]"
>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 188.8.131.52 from your DSL provider and 184.108.40.206 through your cable
>provider, both of those addresses are single-homed from your perspective. If
>someone on the internet sends a packet to 220.127.116.11, 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. 18.104.22.168/24.) 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 22.214.171.124, for example), I "extrude" an
>IP, say 126.96.36.199. 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 188.8.131.52, the server responds with its own MAC.
>Your router at the office has a DSL and cable connection, with IP 184.108.40.206 and
>220.127.116.11 from your respective providers. What I do now is to set up two GRE
>tunnels, one from 18.104.22.168 to 22.214.171.124 and one from 126.96.36.199 to 188.8.131.52. So
>now your home router actually has four routes: DSL-to-world, cable-to-world,
>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 184.108.40.206.
>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 220.127.116.11 and heads out through any of the providers that
>he has available. It reaches the destination, and a response comes back to
>18.104.22.168. 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
>22.214.171.124 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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