My book: 'Running IPv6' by Iljitsch van Beijnum BGPexpert My book: 'BGP' by Iljitsch van Beijnum

Home · BGP Expert Test · What is BGP? · BGP Vendors · Links · Archives · Books · My BGP Book

BGP (advertisement)

Table of contents (for this page):

inet⁶ consult

If you could use some help with BGP, have a look at my business web site: inet6consult.com.

BGP routing courses

Several times a year I teach a hands-on BGP training course in association with NL-ix. The course 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 or a VM running the Quagga routing software.

We'll have dates for the 2020 courses shortly.

Go to the NL-ix website for more information and to sign up. The location will be The Hague, Netherlands.

Interdomain Routing & IPv6 News

  • Search for:
  • IPv4 now also exhausted in Africa (posted 2020-01-16)

    As of a few days ago, IPv4 has run out in all regions in the world, as AFRINIC, the Regional Internet Registry that serves Africa, has now reached IPv4 exhaustion phase 2.

    For more on the IPv4 exhaustion over the last decade, see my story The rise of IPv6 and fall of IPv4 in the 2010s.

  • The rise of IPv6 and fall of IPv4 in the 2010s (posted 2020-01-08)

    The 2010s were the decade that we ran out of IPv4 addresses and the decade that IPv6 deployment got underway—but IPv4 is still going strong even without a fresh supply of addresses.

    Here's an overview of what happened with IPv4 and IPv6 in the 2010s.

    Read the whole article

  • ❝Beating BGP is harder than we thought❞ (posted 2019-12-30)

    In a paper for the HotNets'19, seven researchers admit that "beating BGP is harder than we thought". (Discovered through Aaron '0x88cc' Glenn.) The researchers looked at techniques used by big content delivery networks, including Google, Microsoft and Facebook, to deliver content to users as quickly as possible. This varies from using DNS redirects to PoPs (points of presence) close to the user, using BGP anycast to route requests to a PoP closeby and keeping data within the CDN's network as long as possible ("late exit" or "colt potato" routing).

    Turns out, all this extra effort only manages to beat BGP as deployed on the public internet a small fraction of the time. So it's probably not really worth the effort. Also interesting: when BGP is worse, that's usually consistent over relatively long timescales, and when things deteriorate over one path, they tend to also get worse over alternative paths.

    That seems strange, as the authors observe that "BGP, the Internet’s inter-domain routing protocol, is oblivious to performance and performance changes." However, BGP isn't deployed in a vacuum. People either install capacity where BGP is going to use it, or they tune BGP parameters to use capacity that's installed.

    So having automated traffic management doesn't seem to help much—or does it? Maybe all paths deteriorate together because the automated traffic management solutions do their job and distribute the traffic equally over the available paths, keeping performance the same.

    However, there are some cases when one of the options (regular BGP, anycast, late exit, DNS redirect) performs a lot poorer than the alternative(s). So it's probably more important to focus on avoiding really bad paths rather than trying to pick really good ones.

    Also interesting: apparently ISPs rarely include the EDNS client subnet option, which DNS redirect really needs to work well. However, the Google and OpenDNS/Cisco public DNS services seem to do support it (but not CloudFlare), so if you're experiencing poor performance towards a CDN, you may want to try using the Google or OpenDNS DNS servers.

    Download the paper here.

  • Slides: AS paths: long, longer, longest (posted 2019-11-29)

    Presentation slides from my lightning talk "AS paths: long, longer, longest" at the RIPE-79 meeting in Rotterdam, 18 October 2019.

Archive 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 Security

BGP 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:

  • Secure BGP (S-BGP) is developed by Bolt, Beranek and Newman (BBN). It has been around for several years and there is a proof-of-concept implementation. S-BGP tries to secure all aspects of the BGP protocol, and subsequently needs several signature checks for each BGP update, making the protocol relatively heavy-weight. You can see my earlier rants on S-BGP at the top of this page. Note that I'm not as anti-S-BGP as I used to be any more, although I still think implementing the protocol will be expensive because routers will need lots of extra memory (up to four times as much) and CPU power (possibly dedicated crypto hardware) and this aspect deserves some serious attention.

    Secure BGP (S-BGP) index at BBN.

  • Secure Origin BGP (soBGP) has surfaced fairly recently and hails from Cisco. There are no implementations so far. soBGP mainly focusses on securing the relationship between prefixes and the source AS number, and doesn't need as many computationally expensive checks as S-BGP. However, the protocol can easily be expanded to perform more checks.

    draft-ng-sobgp-bgp-extensions-00.txt (main soBGP draft)
    draft-white-sobgp-bgp-extensions-00.txt (deployment considerations)

    (If the links don't work, the drafts have expired; you'll have to use a search engine to find them.)

There is now also a different approach to increasing BGP security using an "Interdomain Routing Validation" service that works independent from the BGP protocol itself. See what I wrote about this in interdomain routing news on this site, or jump immediately to the Working Around BGP: An Incremental Approach to Improving Security and Accuracy of Interdomain Routing paper.

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.

Your host is Iljitsch van Beijnum. Feedback, comments, link requests... everything is welcome. You can read more about me here or email me at iljitsch@bgpexpert. or follow iljitsch on Twitter.

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 Multihoming

If 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.

Want to know more? Read A Look at Multihoming and BGP, an article about multihoming I wrote for the O'Reilly Network.

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.

You are visiting bgpexpert.com over IPv4. Your address is 35.168.111.191.