denIal of Service Providers

 In ITC's Threat of the Week

You may have read some interesting reports in the technical press or hysterical reports in the mainstream media about the Internet ‘breaking’ This week.

Here are some of the facts:

On August the 13th there were a large number of routing failures in the Internet backbone causing some sites to be unavailable from some places. The loss of access to sites such as eBay and Facebook whipping up ‘the fear’ itself, is this the start of a global pandemic? Should we prioritise fixing this over Ebola etc?

The Border Gateway Protocol  (BGP) is used on Internet backbone routers to exchange routes and the Autonomous System (AS) where the routes can be found between themselves.

When God (you mean Cisco, don’t you? Ed) created some of the older backbone routers, the default number of routes that could be stored was set to an arbitrary 512,000 routes by an allocation of memory in a table called the Ternary Content Addressable Memory or TCAM table (how geeky is that?).

Something to be aware of is that this is the default on most equipment and can be increased by the application of some magic runes (on older Cisco kit at least).

So the day would come, in fact it has come when more than 512,000 routes are circulating the InterWebs and some would be dropped because of a lack of resource allocation by routers that have not been appropriately configured by your caring sharing ISP. This has been pithily dubbed 512Day

Incidentally the 512,000 limit was breached it seems because Verizon misconfigured some summarization, DOS-ing the World. Thanks Verizon.

ISPs are all furiously reallocating their TCAM resources as we speak and even on older kit the limit of routes is 1 million, so we should be ok until 1MillionDay (mwahahaha)!

Here at ITC we are astonished at the poor reporting of this issue, not to mention the SHOCK HORROR WORLD RUNS OUT OF IP ADDRESS stuff that is creeping ever near the front page of The Mail and The Express. Honestly.

If you want to read some really in depth analysis of the BGP issue, look no further than the razor sharp guys at BGPMon: https://www.bgpmon.net/what-caused-todays-internet-hiccup/

If you are worried that you may have more than 512,000 routes any time soon, once they let you out, have a read of this article which tells you how to fix the problem: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/117712-problemsolution-cat6500-00.html

If you don’t want to read the technical detail, we are always here to do it for you and advise you appropriately and honestly about how to build and run you network to support your business. Contact us on 020 7517 3900

Author: chloe

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