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BGP and IPv6 routing coursesSeveral times a year I teach two training courses, one about BGP and one about IPv6. The BGP course is half theory and half hands-on practice, and so is the new IPv6 routing course. Previously, we did an IPv6 course without a hands-on part.
The courses consists of a theory part in the morning and a practical part in the afternoon where the participants implement several assignments on a Cisco router (in groups of two participants per router).
Dates for upcoming courses in 2015 are:
Interdomain Routing & IPv6 News
If you liked (or missed) last month's post where I talk about 20 years of BGP, you may be interested in this story for the RouterFreak site that covers the history of inter-domain routing all the way from the GGP protocol in the early 1980s to the present.
You've been seeing the Noction banners on this site for a while now. Maybe you're still wondering what their Intelligent Routing Platform is all about. In that case, you may want to have a look at RouterFreak's review of the IRP.
20 years ago today, I got my first autonomous system (AS) number, marking my entry in the BGP business. (5399, if you're wondering.)
To quote Ferris Bueller: "Life moves pretty fast. If you don't stop and look around once in a while, you could miss it." So let's look back and see what has happened over those 20 years.
This July 30th, at 23:59:60, a leap second was added to Coordinated Universal Time (UTC). Dyn Research posted the following graph on Twitter that shows there was significant BGP update instability for five minutes after the leap second occurred:
Unfortunately, it's not clear why this happened. However, leap seconds have triggered all kinds of mishaps in the past. They're basically miniature Y2K problems. Time and time again, software engineers show that they can't be trusted to take corner cases into account properly.
This does remind me of a situation about a decade ago, where I had a customer that experienced BGP instability every night at the same time. They used Quagga running on Linux machines. We couldn't figure out what the problem was, until we realized that at that very moment, the ntpdate command was run from the cron. ntpdate synchronizes the system clock with an NTP server. As the machine in question had a very poor system clock, this meant that the system's time was adjusted a lot every night, I think a minute or more, but definitely more than 30 seconds.
Which meant that if Quagga had gotten a BGP keepalive message 8 seconds earlier, it now thought that was 38 seconds ago. If BGP is configured with a hold time of 30 seconds, this means that Quagga now thinks the other side has been quiet for longer than the hold time and it'll tear down the BGP session. This is what happened every night for a bunch of BGP sessions. We solved this by running the NTP daemon continuously, so there was never a big adjustment in system time. (Alternatively, just letting the time drift would also have worked.)
The minimum BGP hold time is 3 seconds, so adjusting for an (improperly handled) leap second shouldn't be able to make BGP think the hold time for a session is expired. However, there could be bug somewhere else that impacted BGP.
I'm not sure whether these kinds of issues are a good argument in favor of abandoning leap seconds, as the bugs won't go away, they'll just show up at a less predictable time. But I don't like the current leap second practice, as they're unpredictable, and you can't calculate the time difference in seconds between two dates without taking the entire list of leap seconds into account. I think it would be better to save the leap seconds up and apply them all at the end of a century. Archives of all articles - RSS feed
My Books: "BGP" and "Running IPv6"On this page you can find more information about my book "BGP". Or you can jump immediately to chapter 6, "Traffic Engineering", (approx. 150kB) that O'Reilly has put online as a sample chapter. Information about the Japanese translation can be found here.
More information about my second book, "Running IPv6", is available here.
BGP SecurityBGP has some security holes. This sounds very bad, and of course it isn't good, but don't be overly alarmed. There are basically two problems: sessions can be hijacked, and it is possible to inject incorrect information into the BGP tables for someone who can either hijack a session or someone who has a legitimate BGP session.
Session hijacking is hard to do for someone who can't see the TCP sequence number for the TCP session the BGP protocol runs over, and if there are good anti-spoofing filters it is even impossible. And of course using the TCP MD5 password option (RFC 2385) makes all of this nearly impossible even for someone who can sniff the BGP traffic.
Nearly all ISPs filter BGP information from customers, so in most cases it isn't possible to successfully inject false information. However, filtering on peering sessions between ISPs isn't as widespread, although some networks do this. A rogue ISP could do some real damage here.
There are now two efforts underway to better secure BGP:
The IETF RPSEC (routing protocol security) working group is active in this area.
What is BGPexpert.com?BGPexpert.com is a website dedicated to Internet routing issues. What we want is for packets to find their way from one end of the globe to another, and make the jobs of the people that make this happen a little easier.
Ok, but what is BGP?Have a look at the "what is BGP" page. There is also a list of BGP and interdomain routing terms on this page.
BGP and MultihomingIf you are not an ISP, your main reason to be interested in BGP will probably be to multihome. By connecting to two or more ISPs at the same time, you are "multihomed" and you no longer have to depend on a single ISP for your network connectivity.
This sounds simple enough, but as always, there is a catch. For regular customers, it's the Internet Service Provider who makes sure the rest of the Internet knows where packets have to be sent to reach their customer. If you are multihomed, you can't let your ISP do this, because then you would have to depend on a single ISP again. This is where the BGP protocol comes in: this is the protocol used to carry this information from ISP to ISP. By announcing reachability information for your network to two ISPs, you can make sure everybody still knows how to reach you if one of those ISPs has an outage.
For those of you interested in multihoming in IPv6 (which is pretty much impossible at the moment), have a look at the "IPv6 multihoming solutions" page.
Are you a BGP expert? Take the test to find out!
These questions are somewhat Cisco-centric. We now also have another set of questions and answers for self-study purposes.
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