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Category Archives for "Networking"

The Bufferbloat Bandwidth Death March

Some puzzle pieces of a picture puzzle.Latency much more than bandwidth governs actual internet “speed”, as best expressed in written form by Stuart Chesire’s It’s the Latency, Stupid rant and more formally in Latency and the Quest for Interactivity.

Speed != bandwidth despite all of what an ISP’s marketing department will tell you. This misconception is reflected up to and including FCC Commissioner Julius Genachowski, and is common even among technologists who should know better, and believed by the general public. You pick an airplane to fly across the ocean, rather than a ship, even though the capacity of the ship may be far higher.

The Internet could and should degrade gradually in the face of load; but today’s Internet does not degrade gracefully due to bufferbloat. Instead, performance falls off a cliff. We are lemmings on migration.

The Internet is designed to run as fast as it can, and so will fill any capacity network link as soon as you have any applications that asks to do so. We have more and more such applications, and the buffers get bigger each hardware generation, though usually operated at a small fraction of that possible bandwidth. As soon as a network or network link reaches100% capacity, the usually grossly Continue reading

SDN Business Cases

We have a few problems in the networking construct and as much as I dont want to say,  paradigm, ecosystem, abstraction etc. a million times there may be a couple hundred in the following writeup. The following document are some rationalizations that have come up over the past recent months/years for some new abstractions in networking that […]

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BIGDATA BUBBLE – Infinite Possibilities

If you live in Australia you probably have heard about the Mining Boom, so was the famous “DotCOM bubble” in way back in 199x . Recently, this new buzzword “BigData” in IT data mining space seems to be a new technology trend for many enterprises and Telco’s. They need bigdata to be implemented to solve […]

Five Features of Brocade VCS

Virtual Cluster Switching (VCS) is Brocade's brand of datacenter ethernet switching. VCS allows for the creation of a network fabric that's capable of converging storage and data traffic via standards-based datacenter bridging. It also solves the “Spanning Tree Protocol (STP) problem” by implementing a standards-based TRILL data plane paired with their own control plane in the form of Fabric Shortest Path First (FSPF). This data + control plane enable the “routing” of MAC addresses through the fabric, negates the need for STP, enables the use of all cabled links, and prevents traffic loops. VCS is only (currently) available on the VDX line of switches from Brocade.

In this post I'm going to outline five aspects of VCS that I found particularly interesting or unique. This is a companion article to an earlier one titled Five Functional Facts about FabricPath where I broke down five features of Cisco's fabric technology.

A Milestone Reached: CoDel is in Linux!

Some puzzle pieces of a picture puzzle.The CoDel AQM algorithm by Kathie Nichols and Van Jacobson provides us with an essential missing tool to control queues properly. This work is the culmination of their at three major attempts to solve the problems with AQM algorithms over the last 14 years.

 

Eric Dumazet wrote the codel queuing discipline (based on a quick prototype by Dave Täht, who spent the last year working 60 hour weeks on bufferbloat) which landed in net-next a week or two ago; yesterday, net-next was merged into the Linux mainline for inclusion in the next Linux release.  Eric also implemented a fq_codel queuing discipline, combining fair queuing and CoDel  (pronounced “coddle”), and it works very well.  The CoDel implementation was dual licensed BSD/GPL to help the *BSD community. Eric and others have tested CoDel on 10G Ethernet interfaces; as expected, CoDel performance is good in what’s been tested to date.

Linux 3.5 will likely release in August. So it was less than a month from first access to the algorithm (which was formally published in the AQM Queue May 6) to Linux mainline; it should be about four total from availability of the algorithm to Linux release.  Not bad at all :-).

Felix Fietkau Continue reading

Cisco CUBE v8.5 vs. v8.6 Features

Surprisingly, there is a lot of difference between these 2 CUBE versions. If you are an ITSP and providing SIP trunks to your customer. Make sure you choose the right IOS!! SR# FEATURE CUBE 8.5 CUBE 8.6 1. Support for Updating codecs dynamically X    YES 2. Media DO-EO flow around X YES 3. High […]

SDN for Internet Providers Use Case

In the bag of magic tricks that SDN has the potential to add as our networks get decomposed over the next few years is self provisioned provider edge nodes. Forget OpenFlow in this, as that is a wire protocol that is vital, but a small and important component of the bigger picture. OF is extremely […]

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What is a Fabric Extender

In this post I would like to cover the base of what is needed to know about the Cisco Fabric Extender that ships today as the Nexus 2000 series hardware. The Modular Switch The concept is easy to understand referencing existing knowledge. Everybody is familiar with the distributed switch architecture commonly called a modular switch: […]

The Next Nightmare is Coming

BitTorrent was NEVER the Performance Nightmare

BitTorrent is a lightning rod on two fronts: it is used to download large files, which Some puzzle pieces of a picture puzzle.the MPAA sees as a nightmare to their business model, and BitTorrent has been a performance nightmare to ISP’s and some users. Bram Cohen has taken infinite grief for BitTorrent over the years, when the end user performance problems are not his fault.

Nor is TCP the performance problem, as Bram Cohen recently flamed about TCP on his blog.

I blogged about this before but several key points seem to have been missed by most: BitTorrent was never the root cause of most of the network speed problems BitTorrent triggered when BitTorrent deployed. The broadband edge of the Internet was already broken when BitTorrent deployed, with vastly too much uncontrolled buffering, which we now call bufferbloat. As my demonstration video shows, even a single simple TCP file copy can cause horrifying speed loss in an overbuffered network.  Speed != bandwidth, despite what the ISP’s marketing departments tell you.

But almost anything can induce bufferbloat suffering (filling bloated buffers) too: I can just as easily fill the buffers with UDP or other protocols as with TCP. So long as uncontrolled, single queue Continue reading

Troubleshooting Common OpenStack Errors

##############General Tips############## /*Check all services $nova-manage service list (check for XXX or smiley face) Binary Host Zone Status State Updated_At nova-scheduler openstack1 nova enabled :-) 2012-05-12 22:42:14 nova-compute openstack1 nova enabled :-) 2012-05-12 22:42:12 nova-network openstack1 nova enabled :-) 2012-05-12 22:42:14 $ ps -ea | grep nova 11448 ? 00:02:54 nova-cert 12072 ? 00:02:57 nova-network […]

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Cisco UCS B440 Blade Replacement

Cisco announced recently a replacement program for their B440 blades (M1 and M2) http://www.cisco.com/en/US/ts/fn/634/fn63430.html Something I noticed on the front of each blade, where the model is shown, the new generation blades (replacements) have the black background with the silver text, shown as the top blade on the picture below: However, the old blades still have the black text with no background. An interesting way to identify the newer generation of hardware.

Cisco UCS B440 Blade Replacement

Cisco announced recently a replacement program for their B440 blades (M1 and M2) http://www.cisco.com/en/US/ts/fn/634/fn63430.html Something I noticed on the front of each blade, where the model is shown, the new generation blades (replacements) have the black background with the silver text, shown as the top blade on the picture below: However, the old blades still have the black text with no background. An interesting way to identify the newer generation of hardware.

N5K Stuck in Boot Mode

Another trivial post. The upcoming posts following this one will take a more in-depth look at the Nexus technologies. So you do an non-ISSU NX-OS upgrade on a Nexus 5000 switch and something goes wrong. After reload you get the following prompt: The switch did not successfully boot from the images it was suppose to. […]
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