My EtherealMind» Design

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.

Webinar on SDN & OpenFlow – Sponsored by Big Switch – Open Attendance

Greg Ferro — Mon, 05 Dec 2011 18:26:31 +0000

I'm pleased to announce that Big Switch have agreed to sponsor SDN & OpenFlow Webinar on February 7th, 2012 and that the event will be free and open to anyone to attend. Are you a Network Architect or Designer ? Are you responsible for strategy, long term vision, or simply keeping track of upcoming technologies ? If so, you will need to know more about OpenFlow and Software Defined Networking and how it impacts the future of Networking in software and hardware. And now, thanks to sponsorship from BigSwitch Networks, anyone can attend.

Ethernet Jumbo Frames, Full Duplex and Why Jumbo Frames Are 9000 Bytes)

Greg Ferro — Sat, 03 Dec 2011 16:14:26 +0000

I've been doing some research into Ethernet and the use of Jumbo frames for some content I've been writing and come across something interesting. The documents state that Jumbo frames can only be used on Full Duplex Ethernet connections.

Modular Data Centre – On the Highway

Greg Ferro — Tue, 22 Nov 2011 15:25:06 +0000

Saw this modular data centre rolling down the highway today.

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.

Requirements Terminology – Defining MUST, SHOULD and MAY

Greg Ferro — Tue, 20 Sep 2011 15:30:19 +0000

One of the problems of working with the PRINCE2 practitioners is that the people tend to get highly focussed on definitions in the Scope of Works. A Scope of Works defines what the deliverables the customer is to received. The problem with a Scope of Works is that it is usually prepared before the work is started and/or fully understood. maybe you have a Gap Analysis, or a Consulting Reports or a Requirements Document to setup the initial engagement (every company has their own name of the same thing).

What Is an Ethernet Fabric ?

Greg Ferro — Thu, 21 Jul 2011 17:30:11 +0000

Define "Ethernet Fabric"

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

What Is the Definition of a Switch Fabric ?

Greg Ferro — Wed, 29 Jun 2011 23:19:04 +0000

The marketing people in IT tend to be overwhelmed by complexity and deep technology. For many liberal arts graduates, they take the drowning option and latch onto certain terms and then grossly abuse it. The most egregious abuse today is "cloud" but "fabric" comes a close second. In this series of posts I want to look at what is a FABRIC and provide a canonical look at what it does and how it works for us.

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.

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.

Review: HP and Optical Backplanes

Greg Ferro — Sun, 15 May 2011 13:05:19 +0000

There were a lot of cool things at InterOp, but not much that was new from the big vendors. For example, Cisco didn't announce anything, probably waiting announce at Cisco Live in July where they can control the press and message much more tightly. However, HP announced the A10500 switch (action pictures ) which is a new campus switch and Gnodal arrived with new products.

However in the centre of the HP stand there was something very cool - a prototype E8212 ProCurve switch with a fully optical backplane.

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.

HP A10500 FlexiCampus – Action Pics

Greg Ferro — Tue, 10 May 2011 15:29:50 +0000

I wanted take a quick look at the guts of the A10500 switch because its got some interesting features. And since no one else in the press even looked at the box, I feel it's necessary to do some nerd action photos with the line cards.

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.

“Can I Haz a “I ? OpenFlow” Sticker Pleez” – Why, Yes, Yes I Can!

Greg Ferro — Tue, 05 Apr 2011 16:16:07 +0000

I tweeted "an I haz a "I ♥ OpenFlow" sticker pleez" - just got a call....

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.

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 [...]

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.

Colour Blindness, Network Diagrams and Reliability

Greg Ferro — Thu, 03 Mar 2011 11:14:54 +0000

It's a lesser known fact that one in ten caucasian males have colour blindness. In networking, we often rely on colour diagrams and coloured cables for a key services. Have you ever given any consideration to colour in your designs ?

TCAM – A Deeper Look and the Impact of IPv6

Greg Ferro — Wed, 26 Jan 2011 15:28:41 +0000

The thing about TCAM memory is that it can be big killer for IPv6 migration. Why ?