Blog Posts in December 2010

Cleaning the Inbox: Internet-related Links

Every Internet-related post is a great opportunity to increase comment count. I’ll pass this time, here are the articles I found interesting with little or no comments from my side. First the generic Internet:

And then my favorite controversy:

see 2 comments

Can You Run OSPF over DMVPN?

Ian sent me a really good OSPF-over-DMVPN question after watching my DMVPN webinar:

In the DMVPN webinar you discuss OSPF design and configuration. However, Cisco design guide says you should use a different routing protocol from what you use on your LAN but you seem to suggest it is okay to extend your OSPF network out to the DMVPN edge by continuing to use OSPF albeit in a different area.

The main issue you face when running OSPF over DMVPN is scalability: OSPF does not scale as well as other routing protocols when used over DMVPN.

read more see 3 comments

MLAG and Load Balancing

FullMesh added an excellent comment to my Multi-Chassis Link Aggregation (MLAG) and hot potato switching post. He wrote:

If there are two core routing switches and two access switches which are MLAGged together in both directions, and hosts that are dual-active LAGged to the pair of access switches, then the traffic would stay on whichever side the host places it.

He also opened another can of worms: load balancing in MLAG environment is dictated by the end hosts. It doesn’t pay to have fancy switches that support L3 or L4 load balancing; a stupid host implementing destination-MAC-address-based load balancing can easily ruin your day.

read more see 5 comments

Cleaning the Inbox: Networking Links

I published this blog post in December 2010. As I was cleaning it up 10 years later, only three out of original 11 links still worked. Whatever…

Some Internet Architectural Guidelines and Philosophy – a must-read for people inventing crazy schemes like load balancing based on unicast flooding or MAC-over-MAC proprietary network virtualization (you know who you are but I doubt you read RFCs or my blog).

Spoofing Google search history with CSRF – like we didn’t have enough security problems, here’s another one.

So what's the MTU on that? The MTU surprises never stop.

see 2 comments

Internet-related links (2010-12-19)

GigaOm published two interesting articles by Joe Weinman: in the first one, he describes why pay-per-use residential broadband Internet is probably inevitable, in the second one he predicts changes in user behavior if the service providers decide to implement it. I would also suggest you take time and read his in-depth Market for Melons article.

Obviously, collecting money costs money and the pay-per-use model is no exception (not to mention that most people would pay less), so the service providers prefer usage caps. There are numerous ways to implement usage caps, but implementing usage cap as an acceptable use policy and calling exceeding the cap policy violation is not the way to do it. Some people are truly trying to alienate the users.

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Yearly subscription to my webinars

A while ago I got an interesting challenge from one of my readers: “I would like to attend a few of your webinars, but the problem I have is that I’m interested in most of them. Is there something we can do?” After a few e-mails, we nailed down the concept I had been playing with for quite a while: yearly subscription package. It gives you three unlimited access to all live webinars and year-long access to all the materials and all the recordings I ever made for a fixed price. You can find a detailed description, list of all recordings and list of all available materials on my web site.

Buying the yearly subscription is easy: select the first webinar you’re interested in (the list of upcoming webinars is also on my web site) and buy the Yearly subscription ticket when registering; you can also buy directly from my web site. You’ll get access to the recordings and PDF materials a few minutes after the registration.

see 4 comments

HP Virtual Connect: every vendor has its own dinosaurs

I was listening to the HP Virtual Connect (VC) PPP podcast recently and got the impression that HP VC is a weirdly convoluted product. I started wondering what exactly they were thinking when they were designing it ... and had the epiphany when Ken Henault took a step back and explained the history leading to the current complexity (listen to the Packet Pushers podcast to get the whole story)

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How much IPv6 address space should a residential customer get?

A while ago I wrote about IPv6 addressing challenges some ISPs face and recommended what I thought was agreed-upon practice of giving residential customers a /64 or a /56. Not long after, I received an e-mail from an IPv6 guru saying:

[Worse] is when people start claiming to have expertise in IPv6 and promulgate this idea of residential /56s and /64s as immutable fact. The reality is that it is becoming more and more apparent that /56s and especially /64s to residential customers are going to be harmful to future innovation in IPv6.
read more see 35 comments

Multi-Chassis Link Aggregation (MLAG) and Hot Potato Switching

There are two reasons one would bundle parallel Ethernet links into a port channel (official term is Link Aggregation Group):

  • Transforming parallel links into a single logical link bypasses Spanning Tree Protocol loop avoidance logic; all links belonging to the port channel can be active at the same time (see also: Multi-Chassis Link Aggregation basics).
  • Load sharing across parallel links in a port channel increases the total bandwidth available between adjacent L2 switches or between routers/hosts and switches.

Ethan Banks wrote an excellent explanation of traditional port channel caveats (proving that 1+1 sometimes does not equal 2); things get way worse when you start using Multi-Chassis Link Aggregation due to hot potato switching (the switch tries to forward packets toward destination MAC address as soon as possible) used by all MLAG implementations I’m familiar with.

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CLNP and the Multihoming Myths

When IESG decided to adopt SIP, not TUBA (TCP/UDP over CLNP) as IPv6, a lot of people were mightily disappointed and some of them still propagate the myths how CLNP with its per-node addresses would fare better than IPv6 with its per-interface addresses (you might find the writings of John Day on this topic interesting and Petr Lapukhov is also advocating this view in his comments).

These views are correct when considering small-scale (intra-network) multihoming, but unfortunately wrong when it comes to Internet-scale multihoming, where CLNP with TCP on top of it would be as bad as IPv4 or IPv6 is (routing table explosion due to multihoming is also one of the topics of my Upcoming Internet Challenges webinar).

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Can we go back to CLNP?

Paulie, a frustrated enterprise IPv6 early adopter summarized his pains in a comment to my “Small-site multihoming in IPv6: mission impossible?” post saying “[IPv6/IPv6 support] is a mess and depressing” and asked “Is it too late to go to CLNS?”

Quite a few old-timers (I’m definitely one of them) lament the glory days of VMS, DECnet Phase V and CLNP, but while CLNP was a viable alternative for the next-generation IP in 1993, it would fare worse than IPv6 today.

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Another security product killed

We all knew MARS is becoming a dead end (Cisco first removed third-party support and then stopped developing the product), now it’s official. MARS is dead.

Just in case you haven’t noticed, this is the third security product (after WAF and XML Gateway) Cisco has killed this year. Are they implementing borderless networks or trimming down to core competences while preparing for onslaught of market adjacencies?

see 8 comments

Chinese BGP incident: was it a traffic hijack?

You’re probably familiar with the April fat fingers incident in which Chinanet (AS 23724) originated ~37.000 prefixes for about 15 minutes. The incident made it into the annual report of US Congress’ U.S.-China Economic and Security Review Commission (page 243 of this PDF) and the media was more than happy to pick it up (Andree Toonk has a whole list of links in his blog post). We might never know whether the misleading statements in the report were intentional or just a result of clueless technical advisors, but the facts are far away from what they claim:

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Small Site Multihoming in IPv6: Mission Impossible?

Summary: I can’t figure out how to make small-site multihoming (without BGP or PI address space) work reliably and decently fast (failover in seconds, not hours) with IPv6. I’m probably not alone.

Problem: There are cases where a small site needs (or wants) to have Internet connectivity from two ISPs without going through the hassle of getting a BGP AS number and provider-independent address space, and running BGP with both upstream ISPs.

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Requirements for IPv6 in ICT equipment

Greg Ferro reached an interesting conclusion after going through my Content over IPv6 presentation: we won’t see IPv6 for a few years, so why bother. Although I disagree with his approach, he may be right ... but if you decide to ignore IPv6, you might be forced to implement it in a hurry, at which point you’ll be stuck if your equipment won’t support IPv6. The very minimum you need to do today is to buy IPv6-ready gear (and yell at the vendors if they try to charge extra for IPv6 support).

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