Tour 2011, part 3: Traffic Congestion on the Internet Highway

This week has been predicted as the week the IPv4 address space gets used up.  Or, at least, completely allocated.  But, that’s just one problem with the increased usage on the Internet.  With network address translation (common in home networks, wireless networks, and small businesses), millions of computers are hidden in private LAN address blocks, so the address space problem isn’t as dire as you might think.

But, as we travel across the country, we have had increasing issues with wireless interference.  There are so many access points in so many places, the chances of channel collisions are quite high.  In two of the cities we have stayed so far, the wireless access points in two physically adjacent businesses have ended up on the same channels, resulting in enough interference to prevent Internet access.  Our computer gets an address assigned, from the selected ESSID, but getting a DHCP address through broadcast is very different than getting communications through on the channel, so the effect is no data transfer.

The solution we use at Chaos Central, where we, of course, control the wireless access point, is to select a different channel.  However, the staff at coffee shops and motels are  neither trained nor authorized to perform this simple action, so they just shrug and mumble something about asking the manager to call the phone company or guessing that it is just normal traffic congestion on their network and telling customers to just wait it out.

The phone company has similar issues.  Even if your internet service provider has a Class B network, only 65,000 clients can be served concurrently.  Like the airlines and hotels overbooking, they can certainly sell more accounts than they have addresses for, with the likelihood that not all the account holders will have their computers on at the same time.  The tricky part is how to deal with the possibility that the address space (or local DHCP scope) gets completely used up.

In high-usage areas across the country, we have noticed that wireless connections get dropped frequently, either after a specific time period, say 30 to 45 minutes, or after a period of inactivity, typically 3 to 5 minutes.  This also seems to be happening on the DSL networks, as the IP address at Chaos Central shifts from time to time, even though the modem is always on.

Now, such arbitrary disconnections often go unnoticed, if all you are doing is browsing web pages or reading email, but trying to run a VPN connection, encrypted tunnel, or large file upload or download is a trying experience with loss of connections.  A few weeks ago, this was happening at Chaos Central at an alarming rate: calls to the DSL provider’s tech support claims that “it must be your modem,” even though a DHCP client will normally ask for the same address if the connection drops.  However, the reconnect rate improved after the call, even before we replaced the modem (which was an old model anyway).  After a few weeks, the new modem changes address now and then, indicating to the Unix Curmudgeon that the problem is not so much with bad phone lines and cheap modems, but with traffic congestion on the network.

When a connection drops, whether because of deliberate disconnection due to timeouts or duration policies, if the modem gets a new address it is because the old one was issued to someone else in that brief time required to re-establish the connection.  Which, of course, means that there are more active accounts than available addresses, either in the network or in the DHCP zone for that circuit.

Obviously, in stressed economic times, things are going to get worse before they get better.  But, change is coming soon.  Like the splitting of states and metropolitan areas into multiple area codes to accommodate the explosion of “one person, one phone number” caused by Centrex dialing for businesses and personal cell phones, access to the Internet will undergo a revolution.  First, to implement IPv6, in which the hardware address of the network card in your computer is added to the IP address to expand the address space without network address translation, and second, to expand the wireless networking protocols to incorporate more channels and intelligent adaptive interference avoidance.

Meanwhile, we’re back to the early days of limited wireless access, seeking out connections where we can.  And, we deal with the mutable addresses at Chaos Central by having programs running that post the current address to a secure file location on our public web servers, so we can always login remotely.  Change is sometimes progress, and sometimes just an adventure.