Thread: Connect WIFI & 3G
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egoshin is offline egoshin
2010-03-30 , 19:02
Posts: 992 | Thanked: 995 times | Joined on Dec 2009 @ California
#6
Originally Posted by rambo View Post
I'm not quite following you here, I can easily do "load-balancing" between two network connections on my linux fw (no-brand white box HW), by routing one set of TCP-streams via one interface and other set via another (main and backup network connections, the backup one is puny but every little bit helps...). No real multi-homing needed.
How your Linux box knows - which connection it should use to send packets to www.cnn.com? (we speak about load-balancing but not backup)

I can imaginate 3 possibilities:

1) statically define and that is not a case for mobile device like N900.

2) don't care. That actually means that all your outcoming traffic goes to one interface which has 'default' route, and second interface is used as backup. It is not needed in case of N900 - it has autoconnection feature.

3) randomly split TCP via interfaces. It is an attempt of acceleration of your traffic on expense of both providers. It works in case of multiple TCP connections (see P2P case below).


The 4th possibility - get routing info from both network providers - requires installation of BGP protocol handler AND (!) convincing both providers to accept your Autonomus System number.


Now for a single tcp-stream download (http, ftp, etc) this does not help at all, but browsers usually open at least two tcp streams per server to request data faster (why using multiple parallel streams is usually faster in practise even without simple connection balancing has to do with pecularities of TCP in the real world) and many sites load data from multiple servers.
This kind of load-balancing actually gives your browser the speed of LOWEST interface speed and inherits the biggest delay time of both networks. In case of ground network it is usually not a problem but 3G and WiFi have very different delays and bandwidths.

P2P applications abuse the proverbial ton of TCP-streams so they can practically fully utilize such setups.
You right about P2P, on high bandwidth application with many TCP the latency has no serious meaning... but it can't use an incoming connections and your device is restricted to connections of only inbound acceptable servers.

However, I don't consider P2P for N900 seriously. Moreover, the 3G provider network design effectively stops multiple TCP connections from a single N900 - N900 works behind NAT router with a restrictive resources.
 

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