Internet outages and slowdowns spiked earlier this week, and more are likely on the way in coming weeks, as the internet grows too big for some network hardware to handle.

According to Vancouver-based internet monitoring firm BGPMon, this past Tuesday, outages were "well above the daily average" and the number of affected systems and addresses was "the highest we've seen in the last 12 months."

The issue arose when the number of routes on the internet temporarily jumped beyond 512K (512 kilobytes or 524,288, since a kilobyte is 1024 bytes) — the maximum that some older networking gear can handle by default.

The cause was a bug at U.S. internet service provider Verizon that dumped 15,000 new internet destinations onto the network for about 10 minutes, said Andree Toonk, founder and lead developer for BGPMon.

"We basically got a small taste of what is possibly about to happen," added Toonk, whose company monitors internet routing for outages and security incidents. "Hopefully this is a wakeup call."

Network analysts such as Toonk estimate the number of routes in the internet — currently hovering around 500,000 — will permanently surpass 512,000 within a month.

"The real test… will start later this week, and will be felt nearly everywhere by the end of next week," estimated Jim Cowie, chief technology officer and co-founder of network performance management firm Renesys, in a blog post Tuesday.

The hardware causing the problem is older routers made by San Jose, Calif.-based Cisco and still used by many smaller networks and regional internet providers, Toonk said.

Nuisance, not threat

According to Cowie, most larger internet service providers "and certainly all of the routers that operate the core infrastructure of the internet" use newer hardware that is unaffected.

That means the issue is more of a nuisance than a threat to the internet.

The problem arises because routers direct internet traffic to the correct destination, and rely on summaries of the routes and destinations that are kept in tables in their memory. The default maximum size of that memory is 512K for older routers. Once that maximum is reached, three possible things can happen, Toonk said:

The router can switch to a slower mode, resulting in sluggish performance.

Some destinations may not end up in the table at all, making them unreachable.

The network operator may have to reboot the router, resulting in a few minutes of instability.

Internet users will experience:

Overall internet slowness if they rely on an internet service provider that's affected.

Slowness for certain websites or services that rely on affected internet service providers, even if their own ISP is not affected.

Cisco had warned users of the impending problem back in May.

"It's time to start preparing," wrote Omar Santos, senior incident manager of Cisco's Product Security Incident Response Team, in a post on the Cisco Support Community website.

He suggested some fixes, such as changing the default configuration for affected devices, but noted that might require users to reset the device.

Toonk said that likely would only take five minutes, but isn't always easy to schedule on networks that serve hundreds or thousands of people. He hopes that after this week's warning, affected internet service providers will make a special effort to proactively rejig their routers.

"But it's not unlikely we will see some slowness or instability over the next few weeks," he added. "If people don't fix it, it will happen again, and there will always be people who won't fix it."