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Christian Nimsky's Weblog

Poor Man's T-1

Christian Nimsky

SMCBR21VPN.jpg

One of the things that you get with a T-1 line is a guaranteed bandwidth and (usually) sub-4 hour recovery from any outages in connectivity to the internet. As many households become more dependent on the internet (particularly with VOIP) downtime can be almost as crippling as it would be to a business, however T-1s usually carry with them a cost between $300 and $700 per month for such security. Until now. The advent of new, inexpensive Dual-WAN (also called multi-homing) routers, there is another way consumers can achieve redundancy by using two inexpensive ISP connections.

Here at Nimsky Operations Central, we are heavily dependent on internet access. We might not notice if our satellite TV goes out but if you mess with our internet you better watch out. We use a premium cable modem connection (15MB down, 5MB up) and pay more for it, but as our neighborhood has gotten fully “online” sometimes the connection goes down. Not often, but sometimes. We have a VOIP line, Skype, two Wi-Fi cell phones running UMA, we use Amazon S3 for file and photo storage, we do other digital photo and video uploads, we’re on Pandora and iTunes, we have three active PCs in the household, etc. and downtime just doesn’t work for us anymore. Then I saw a promo for a cheap DSL service for $14 a month. Its only 768 kbps down and 128 kbps up but its a great backup line and can keep our key services “lit” even if the cable modem is down.

Rather than have just a backup line though, I wanted to put that bandwidth to work and not just leave it idle. At a startup I founded I put in a T-1 line with DSL backup using a beefier multi-homing router and I wondered if the same could be had in consumer grade.  So, I researched dual WAN routers and (after one mis-fire that I will neglect to name here) I found a gem: SMC makes a SOHO-oriented Dual-WAN wired router that is easy to set up and does a pretty good job of balancing two consumer-grade ISP connections.  The model number is SMCBR21VPN and it could be had for about $360 on Buy.com.  I already have a wireless access point so really what I needed was a box that blended traffic from two ISPs into a single stream and then administered DHCP internally with basic firewall functionality.  The SMCBR21VPN does that very well without a lot of the extra “fluff” that consumer-grade routers have today.  See below for a sample graph of my ISP usage over the last 24 hours.

stats_packet_in_1225749730.png

What you see is a typical, low-traffic Monday with some light activity in the morning before work, relatively little until my wife comes home and then a bunch of phone traffic around 10pm PST.  In this sample the cable modem is WAN 1 and the DSL is WAN 2.  The router can be set to “know” that WAN 1 has more bandwidth than WAN 2 and to favor WAN 1, but yet it still uses WAN 2 when things pick up enough.  When I really pump files through the network the graph underscores this effect; I’ve tried some non-scientific tests to see if under very heavy load the device can add together the total bandwidth of each line and it appears to do so.

The SMCBR21VPN also does what you would expect for fail-over: If you unplug one WAN port it shunts all traffic over to the other WAN port.

So, in the end game, I invested the equivalent of one month’s T-1 fees to get what I bet is nearly equivalent uptime and some extra bandwidth in the bargain.