Blog Posts in April 2013

Open vSwitch Under the Hood

Hatem Naguib claimed that “the NSX controller cluster is completely out-of-band, and never handles a data packet” when describing VMware NSX Network Virtualization architecture, preemptively avoiding the “flow-based forwarding doesn’t scale” arguments usually triggered by stupidities like this one.

Does that mean there’s no packet punting in the NSX/Open vSwitch world? Not so fast.

read more see 4 comments

They want networking to be utility? Let’s do it!

I was talking about virtual firewalls for almost an hour at the Troopers13 conference, and the first question I got after the presentation was “who is going to manage the virtual firewalls? The networking team, the security team or the virtualization team?”

There’s the obvious “silos don’t work” answer and “DevOps/NetOps” buzzword bingo, but the real solution requires everyone involved to shift their perspective.

read more see 1 comments

Why are 3G networks so slow?

More than four years ago one of my friends wrote about uselessness of UMTS connections (the page has decayed into digital wasteland in the meantime) for inter-router backup links and although I got numerous comments trying to explain the issues I never found a good explanation that a simplistic networking engineer like me could understand.

Ilya Grigorik fixed that. His Breaking the 1000 msec Time-to-Glass Mobile Barrier talk has some real-world statistics, and a fantastic description of how 3G/4G networks work and what causes the enormous latencies. His High Performance Browser Networking book has even more details. Enjoy!

see 1 comments

Resiliency of VM NIC firewalls

Dmitry Kalintsev left a great comment on my security paradigm changing post:

I have not yet seen redundant VNIC-level firewall implementations, which stopped me from using [...] them. One could argue that vSwitches are also non-redundant, but a vSwitch usually has to do stuff much less complex than what a firewall would, meaning chances or things going south are lower.

As always, things are not purely black-and-white and depend a lot on the product architecture and implementation.

read more see 9 comments

Virtual Appliance Performance Is Becoming a Non-Issue

Almost exactly two years ago I wrote an article describing the benefits and drawbacks of virtual appliances, where I listed virtualization overhead as one of the major sore spots (still partially true). I also wrote: “Implementing routers, switches or firewalls in a virtual appliance would just burn the CPU cycles that could be better used elsewhere.” It’s time to revisit this claim.

read more see 16 comments

VM BPDU spoofing attack works quite nicely in HA clusters

When I wrote the Virtual switches need BPDU guard blog post, I speculated that you could shut down a whole HA cluster with a single BPDU-generating VM ... and got a nice confirmation during the Troopers 13 conferenceERNW specialists successfully demonstrated the attack while testing the security aspects of a public cloud implementation for a major service provider.

For more information, read their blog post (they also have a nice presentation explaining how a VM can read ESXi hard drive with properly constructed VMDK file).

see 7 comments

This Is What Makes Networking So Complex

The responses to my What did you do to get rid of manual VLAN provisioning post were easy to predict: a few people sharing their best practices (thank you!), few musings on the future of SDN/networking, and the ubiquitous anonymous rant against stubbornness and stupidity of networking engineers and their OPEX.

I know one should never feed anonymous trolls, but this morsel is simply too juicy to pass, so here it is – let’s see what makes networking so complex.

read more see 15 comments

Compromised Security Zone = Game Over (Or Not?)

Kevin left a pretty valid comment to my Are you ready to change your security paradigm blog post:

I disagree that a compromised security zone is game over. Security is built in layers. Those host in a compromised security zone should be hardened, have complex authentication requirements to get in them, etc. Just because a compromised host in a security zone can get at additional ports on the other hosts doesn't mean an attacker will be more successful.

He’s right from the host-centric perspective (assuming you actually believe those other hosts are hardened), but once you own a server in a security zone you can start having fun with intra-subnet attacks.

read more see 4 comments

Kickstart free CCNA and CCNP videos!

Andrew Crouthamel had a great idea – he decided to produce free CCNA-level videos and started a Kickstart campaign to get the funding. The initial response was overwhelming, so he included stretch goals: Wireshark training (WCNA – already reached) and CCNP.

He probably underestimated the costs of the project, but that doesn’t really matter. I’m positive he’ll deliver, so let’s help him get started – if only 10% of my readers donate a single morning Frapuccino to his project, he’ll have more than enough funding to get the whole CCNP curriculum done.

see 5 comments

464XLAT Explained

IETF recently published RFC 6877 (464XLAT) describing a dual-translation mechanism that allows an IPv6 host (or CPE) in an IPv6-only access network to pretend it still has IPv4 connectivity. Why would one need a kludge ingenious solution like this? In a word: Skype.

For more details, watch the video explaining the need for 464XLAT and two typical use cases: Android handset and a CPE device (example: SOHO router with 3G uplink).

see 4 comments

Are you ready to change your security paradigm?

Most application stacks built today rely on decades-old security paradigm: individual components of the stack (web servers, app servers, database servers, authentication servers ...) are placed in different security zones implemented with separate physical devices, VLANs or some other virtual networking mechanism of your choice.

The security zones are then connected with one or more firewalls (when I was young we used routers with packet filters), resulting in a crunchy edge with squishy core architecture.

read more see 21 comments

The First Glimpse of Open Daylight

Operating systems are boring (for most people); it’s the applications that make everyone excited. SDN is no different. Controllers are boring – someone has to reinvent all the wheels that the networking vendors have been inventing for the last 30 years before you can develop the sexy stuff ... but not many people outside of ivory towers would start developing the (supposedly) sexy SDN apps until being sure the underlying platform will not disappear into thin air.

read more see 6 comments

Why TCP and HTTP affect web application performance

In the ideal world, you’d get a new web page within 100 milliseconds of clicking an active web page component (link, button ...). Reality is way harsher – sometimes it takes seconds till you can enjoy a web page served from a well-behaved web server (let’s pretend there are no server performance issues).

In the first part of my TCP, HTTP and SPDY webinar I explained how the transport mechanisms (TCP and HTTP) impact the end-to-end web application performance and what you could do to reduce the web page loading time.

add comment

The Impact of Changed NHRP Behavior in DMVPN Networks

Two years ago I wrote the another Fermatish post: I described how NHRP behavior changed in DMVPN networks using NAT and claimed that it might be a huge problem, without ever explaining what the problem is.

Fabrice quickly identified the problem, but it seems the description was not explicit enough as I’m still getting queries about that post, so here’s a step-by-step description of what’s going on.

read more see 6 comments

VLANs are the wrong abstraction for virtual networking

Are you old enough to remember the days when operating systems had no file system? Fortunately I never had to deal with storing files on one of those (I was using punch cards), but miraculously you can still find the JCL DLBL/EXTENT documentation online.

On the other hand, you probably remember the days when a SCSI LUN actually referred to a physical disk connected to a computer, not an extensible virtual entity created through point-and-click exercise on a storage array.

You might wonder what the ancient history has to do with virtual networking. Don’t worry we’re getting there in a second ;)

read more see 8 comments