My EtherealMind» Design

Is OpenFlow Open ? I Ask – Compared to What ?

Greg Ferro — Thu, 09 Feb 2012 21:08:53 +0000

I’ve always wondered whether the Open Networking Foundation is the correct caretaker of the standards process for Software Defined Networking. Recently, we’ve seen some questioning of the direction of those standards on OpenFlow, and, now that we are beginning to understand the concepts of controllers, Software Defined Networking these are good questions to ask. it shows [...]

Comparing Embrane and Nicira Is Pointless – They Are Different

Greg Ferro — Thu, 09 Feb 2012 12:32:51 +0000

Had a few conversations, and some articles, where comparisons are being made between Embrane and Nicira and wanted to point out that there are few similarities between these companies.

Can Fibre Optic Ethernet Cables Be Longer Than the Standard ?

Greg Ferro — Sun, 01 Jan 2012 19:41:10 +0000

Short Answer is "It depends, but usually yes." Long answer follows with a discussion of launch power, receiver sensitivity, and cable losses.

Responding: On Optimizing Traffic for Network Virtualization

Greg Ferro — Fri, 23 Dec 2011 15:10:47 +0000

I'm responding to Brad Hedlund's post "On optimizing traffic for network virtualization" where he seems to missed a key point. It's about cost of ownership in terms of ability to troubleshoot.

Scaling Virtual Appliances With Embrane

Greg Ferro — Mon, 12 Dec 2011 17:07:43 +0000

Embrane uses concepts of IP Flows to scale virtual appliances. Embrane does this by managing IP flows and then directing to other appliances, in effect creating what I would call a two tier load balancing.

Routing Protocols and Computation in Silicon

Greg Ferro — Sun, 27 Nov 2011 08:57:42 +0000

I got this question and I guess it may not be obvious to everyone so I'll have a shot at answering it.

Technology advances in ASIC hardware have resulted in substantial improvements in switching performances of routers and switches. However, the routing processes are still dependent on CPU speeds. What are the existing limitations in router/switch models which prevent route computations from being performed in hardware?

Problems With Cat6A Cables in Data Center

Greg Ferro — Mon, 14 Nov 2011 15:30:04 +0000

I was reading a white paper by Panduit that claims that 10GBaseT is suitable for use. I've been critical of Cat6A cable and believe that it's not suitable for data centre use.

Cisco Nexus 5000 / 2000 Pricing Bundles and Fabric Extension Transceivers (FETs) vs 10GbaseSR SFPs.

Greg Ferro — Thu, 03 Nov 2011 20:18:26 +0000

Recently I noticed that Cisco is selling "Fabric Ethernet Transceivers" for the Nexus switch family. Some research shows that these are replacements for 10GBaseSX SFP modules. Importantly, it's cheaper to install new cabling than to buy 10BaseSR SFP+ modules.

Fibre Connectors

Greg Ferro — Thu, 14 Jul 2011 18:49:26 +0000

A short summary of the Fibre Cable Connectors, description and some notes on usage. This is summary notes and intended for reference.

Soft Switching Fails at Scale

Greg Ferro — Sat, 09 Jul 2011 18:12:05 +0000

There is a significant camp of software developers who are developing software switching solutions for hypervisors. Which is nice, I guess. The use of software switching in the hypervisor has some good points but, in my view they are heavily outweighed by the bad. I present the use case, and show that software

Cisco C6500 Service Modules – Not My Choice, Now.

Greg Ferro — Sun, 19 Jun 2011 20:38:51 +0000

These all suggest that the time for planning and designing Service Modules is over. There are no suggestions that service modules for the Nexus 7000 will be developed that I can see. I can prognosticate that it would slow down the development of the core switch / route / performance functions, and it will be some years before those core capabilities is complete enough that service modules would become viable product development tasks — they might be in development, but not much chance of going into production. [^1] Do I sound bitter about Service Modules ? A bit. I've had a number of hard to solve problems that lasted months before code fixes arrived. I've been fan of the NAM but the price is now far removed from it's practical value. USD$30K List is way over priced for its capabilities and even with a 30% discount, you can buy a lot of network management systems that deliver much better functions and features for that price.

L2 MultiPath Basic Design Differences

Greg Ferro — Tue, 07 Jun 2011 10:02:09 +0000

With all the talk about Layer 2 Multipath (L2MP) designs going on, I just want to point out a fundamental change in the way many people approach network design. It's seems that this point has been lost somewhere in the discussion of protocols. The Spanning Tree Protocol blocks looped paths, and in a typical networks this means that bandwidth is unevenly distributed. Of course, we might use PVST or MST to provide a rough sharing of load by splitting the spanning tree preferences for different VLANs, but the design still doesn't change overall. The basic point is that there is a LOT of bandwidth that is never evenly utilised - and that means wasted power, space and cooling (which costs more than the equipment itself).

VMware: Let’s Get Logical – The Case for OpenFlow Network Virtualization (and Their Failed Network Plans)

Greg Ferro — Thu, 02 Jun 2011 18:35:23 +0000

VMware has made several strategic moves to implement dynamic networking - vSwitch, vDS, Nexus 1000 (in partnership with Cisco), vCloud External Networks (using MAC in MAC of all things) and have basically failed to deliver overlay technology without implementing technology in the network itself. Equally, VMware hasn't been willing to engage with the networking vendors to develop technologies that would solve this problem - VNtag / VEPA/ VEP combined with TRILL / SPBB, instead letting them argue amongst themselves. VMware attempt with vCloud networking using MACinMAC encapsulation seems to have failed and stalled and is getting another attempt using MACinIP. VMware/Xen/HyperV are all desperate to have a more dynamic network that can be controlled from their software and this might be where OpenFlow gets a big lift - as a configuration engine.

PacketShaper and Flow Directions

Greg Ferro — Sat, 14 May 2011 23:45:16 +0000

I stumbled across an old diagram I made a long time ago about the direction of flows on a BlueCoat PacketShaper. Since I've been looking for it for about three years, I've diagrammed it quickly so that it is here for future reference when I'm working PacketWise in the future. PacketShaper PacketWise is one of my very favourite tools for managing traffic flows, and much preferable to PHB QoS aka DiffServ for many types of use cases. An TCP flow has four possible directional attribute related to the use of a inside and outside networks, and whether the flow was initiated from the client to server which sets the "direction" of the flow relative to the Packeteer. The flow is determined by who initiated the three way handshake. For purposes here, the Client always initiates the TCP connection, and the Server terminates the connection.

TCP Session and Direction

Most people understand the three way handshake, but not many consider the direction of the session.
The connection from the client to the server is outbound, but is inbound on the server. And vice versa, the server outbound session is inbound on the client. That's not very useful for being able to define the direction of flows.

Why is direction important ?

Direction of flows is important if you want to configure asymmetric rules. That is, not all protocols require symmetic bandwidth. For example, HTTP traffic is usually a 10:1 ratio for reply to request. That is, a request for this webpage is about 10KB, but the reply with the data, images and javascript is more than 100KB. For an FTP upload server, you might have the reverse condition where the inbound traffic is far more than the outbound. To make the most of your Internet connection for this case, you could configure the inbound bandwidth on your Internet connection to be 80% FTP, 20% HTTP and the outbound bandwidth to be 20% FTP and 80% HTTP. This gives a far better utilisation, especially in regards to better TCP Windowing and overall TCP goodput.

Complex Systems Have Complex Failures. That’s Cloud Computing.

Greg Ferro — Tue, 26 Apr 2011 17:00:48 +0000

Exposing cloud failures The result of the Amazon EC2 failure this week has exposed a number of technology strategies in cloud infrastructure as being less than perfect. Complex systems have complex failures The most vexing problem of Cloud Computing is that these systems are complex, and the more complex system the more complex the failure. [...]

Fate Sharing, Failure Domains and Why VTP Is Awesome

Greg Ferro — Wed, 20 Apr 2011 15:00:10 +0000

A lot of people regard Virtual Trunking Protocol(VTP) as nothing but trouble. Indeed, it's hard to find many people who will implement it on their network. I find this baffling - it's a great tool that dramatically reduces time, errors, and troubleshooting is something that we should all embrace and use wherever we can. Naturally, with great power comes great evil. So, lets be clever instead.

Musing: How Many 10Gigabit Ethernet Ports Do You Really Need ?

Greg Ferro — Mon, 18 Apr 2011 22:11:53 +0000

I was doing a Data Centre Design recently and did some numbers around the numbers of 10 Gigabit Ethernet ports that need to be deployed. I got a bit of a realisation shock.

Which Network Topology?

admin — Sat, 02 Apr 2011 15:30:52 +0000

Recently Iíve come across some interesting terms for variants of common network topologies, so I decided I'd try to list as many of them as I can for reference. Please suggest others to add.

AeroHive, HP, ‘Big Boner’ AP’s and Wireless LAN Controllers

Greg Ferro — Mon, 21 Mar 2011 00:33:24 +0000

There are cool things about being a #TechFieldDay delegate and receiving presentations from multiple vendors is but one. Sometimes it's the only time that you can see the differences in the approach to market. The Wireless networking industry appears to be undergoing a significant shift in the endless centralised/decentralised ecosystem.

Low Level Design – Think About the Next Step

John McManus — Fri, 18 Mar 2011 21:13:58 +0000

A while back Greg wrote a great article about the “Rules of Design Documentation”†http://etherealmind.com/rules-design-documentation-etherealmind/these are really valuable rules when it comes to writing a design document and in my opinion is particularly relevant to a Low Level Design AKA Detailed Design Document. Ask yourself Before you can apply these rules of design you must [...]

Checkpoint/Nokia Firewall Clustering. Uh Oh.

Greg Ferro — Thu, 17 Mar 2011 17:00:37 +0000

I've been reviewing a network that has some CheckPoint firewalls that have been unstable, and while this isn't surprising (in my experience, it's common enough for Checkpoint firewalls to be unstable for some reason or the other), this time I've been faced with Checkpoint Clustering. A few years back I tried to make this work, but gave up when CheckPoint couldn't make it work either. A few years later, I find someone brave enough to attempt it. This time it's different, I'm the one who has to justify why it's a bad idea. Now that the manuals are not secret anymore I think I've found out why.

Explaining L2 Multipath in Terms of North/South, East West Bandwidth

Greg Ferro — Tue, 15 Mar 2011 20:47:59 +0000

Breaking down the definition of North/South and East/West Bandwidth with some nice pictures and examining Layer 2 Multipath and why it fits virtualisation so well.

Citrix Branch Repeater : WCCP or Not to WCCP That Is the Question?

John McManus — Tue, 08 Mar 2011 21:05:13 +0000

Whether ’tis nobler in the network to suffer un-accelerated traffic during an outage or to take arms in the form of Policy Based Routing. When you decide to†deploy†Citrix Branch Repeaters (CBR) you have to†deploy†at either end of the WAN to accelerate and compress traffic between these endpoints. Therefore it would seem sensible to have some [...]

Fault Detection in Metro Ethernet

Tony Brown — Sat, 05 Mar 2011 17:08:20 +0000

Following my article on Loop-Free Alternate Routes, Michael McNamara made a good point about some of the issues detecting failure in a Metro Ethernet network. This seems to be a commonly misunderstood problem.

Cisco ACE – Enterprise Load Balancing on a Stick Using Source NAT – Part 3

Greg Ferro — Mon, 14 Feb 2011 15:15:54 +0000

A detailed look at configuring a Cisco ACE module to do load balancing on a stick. This time with basic configuration for dual VIPs and dual NATs.