Vendor Price Variation on 40 Gigabit SFP Modules – It’s Nuts

In a recent project, I noted an astonishing difference in price of the optical and copper cabling assemblies associated with 10Gigabit Networking. I conclude that some companies are including a “license fee” in the cost of these components and making the overall cost harder to determine.


What Makes Network Appliances Fast ?

The performance of appliances is complex topic. There are four broad aspects of the dedicated hardware to provide the higher performance and three reasons why vendors like selling appliances instead of software VMs. I cover them here.


Cheap Network Equipment Makes a Better Data Centre

TL:DR A recent project bought a low cost network for the data centre. It cost less one-third of the the market leader & half the cost of a well known merchant silicon vendors. As a result, it is planned to last for two, maybe three years before it will be replaced. From this project I learned that “fast & cheap networking” could make a big impact on new data centre designs and business attitudes. Plus it was much more satisfying as a professional project. I’m now wondering – is networking too expensive ?


Blessay: Is the Data Centre “One Network” or “Connected Smaller Networks”

Most people refer to the “Data Centre Network” as though it was a single network. In practice, data centres have a number of individual networks. Each network is specifically designed for a specific purpose and function. A typical data centre network design has about five individual networks that connect together to form the “data centre network” which many people fail to recognise. I’ll define these networks and then look at the future of data centre networks with overlays. What seems clear, today, is that networking will provide different networks for different use cases and the customer will decide.


Visual Guide to LAG Thinking for Server Admins

When working with Server and VMware people, there is a fair amount of misunderstanding of what is happening in the network. The best technical explanation for what is happening in LAG is, of course described at Ivan Pepelnjak’s IPSpace Blog – vSphere Does Not Need LAG Bandaids – The Network Does while Chris Wahl talks about the server side for VMware but I wanted to add something to the debate.


Network Diagrams: Choosing Better and Free Fonts

Making diagrams aesthetically appealing with visual impact is better documentation. Choosing the correct fonts on network diagrams will improve your network diagrams significantly. Here is some work on how to choose a good font and some recommendations on the best free fonts for your machine.


Overlay Networking & VXLAN Means MPLS in the Data Centre is Dead

Overlay networking has been around for a year or so now and the ideas behind it are well established. It was about 3/4 weeks ago while researching VTEP functionality in Dell and Arista switches that I realised I could build manually configured tunnels with VXLAN and get the same results as an EoMPLS x-connect with almost zero effort. More importantly, I don’t have to pay for expensive hardware that has MPLS functions or pay again for software licenses to upgrade with MPLS features.


◎ Tech Notes: Arista AgilePorts – Building 40Gigabit DCI with 10GbE ports

Stumbled over “AgilePorts” feature in Arista products this week: Arista’s AgilePorts technology enables the combination of four 10GbE SFP+ interfaces into a single 40GbE interface leveraging the parallel lane technology present in the 40GBASE-CR4 and 40GBASE-SR4standards. With AgilePorts, each 10GbE interface emulates one of the four parallel lanes, which are then driven by a 40GbE […]


On Diagrams and Information

I’ve been working on a lot of diagrams lately and pondering how to represent network architectures. I’ve been reading The Visual Display of Quantitative Information to get some inspiration on different approaches. I continue to be fascinated by the power of a network diagram that is well thought out and visually pleasing. And this fascination has led to my own focus on different network diagrams. In this post I’m thinking out loud one the different ways to represent information.


Published: Evolving SDN: Tackling challenges for web-scale deployments

I was commissioned by GigaOmPro to write a report on “SDN Challenges in Large Scale Deployments”. I spoke with a number of network and virtualization engineers about their perspectives on SDN, the challenges they faced and how they would use Software Defined Networking in their data centres. It was evident during the research phase is that many people are not clear on what Overlay Networking is and just how deeply Overlay Networking will change Data Centre architecture and especially the nature of the networking and security domains.


◎ Introduction to How Overlay Networking and Tunnel Fabrics Work

In this blog post I’ll make an attempt to summarise Overlay Networking in a couple of paragraphs to act as reference for upcoming blog posts that discuss the nature of Tunnel Fabrics in Physical Network environments. It also has pictures.


Merchant Silicon Evolution, 40GbE arriving in 2015 & Impact on Data Centre Design

I’ve been reading a presentation from Sharkfest 2012 where a engineers from Microsoft are presenting on their
Microsoft’s Demon – Datacenter Scale Distributed Ethernet Monitoring Appliance. The whole presentation is interesting but this particular slide caught my attention:


◎ What’s Happening Inside an Ethernet Switch ? ( Or Network Switches for Virtualization People )

I was going to call this article “Ethernet Switches for Virtualisation Engineers” but, really, everyone should have some understanding of the internals of an Ethernet switch. But particularly I want to focus on how multicast and broadcasts are handled in a high speed, low latency environment like a Data Centre Network.

It’s vital to understand that latency is critical to your application performance. It is common for a single transaction to take hundreds of round trips so a small increase in latency on each round trip has a large impact on the perceived performance. The client will send a chunk of data and wait for acknowledgement. Even setting up the TCP connection takes a few round trip – remember that TCP sessions are setup, and each data transfer is confirmed.

A modern network switch will have latency around 10 microseconds. The Cisco Nexus 7000 is about 8 microseconds & Brocade VDX 8770 claims less than 4 microseconds. There are many reasons why a switch can be faster or slower but I’ll look at a specific example

Remember, the latency interval is the time taken to receive a packet, decode the address, lookup the forwarding table, switch the packet (and copy it if needed) and transmit out of an Ethernet interface. That’s really fast processing. How does an Ethernet switch do this ?


Screencast: Knowledge Management in Technology – Part 1

Network Engineers have to manage a lot of information. Products, technologies, textbooks, study notes and research material as well as new protocols and features. Just simple tasks like keeping product manuals handy for 40 or 50 products is a real problem. How do you keep the information organised, referenced, accessible and useful ?

This three part screencast is about how I manage all the “inputs” so I don’t feel lost in information after many, many people asked.

How to Launch a 65Gbps DDoS, and How to Stop One – CloudFlare blog

Lots in insight for Enterprise people to consider when defending your network against DDoS attacks. At CloudFlare, an attack needs to get over about 5Gbps to set off alarms with our ops team. Even then, our automated network defenses usually stop attacks without the need of any manual intervention. When an attack gets up in […]


Technical Writing Tip for CLI Commands

Saw this nifty documentation idea in the Cisco® Smart Business Architecture (SBA) guide today.

11 Things About Using A Transparent or Layer 2 Firewall ?

You can deploy some modern firewalls in Layer 2 mode such that they are transpart


How TRILL (and SPB) can reduce STP risk and mitigate impact

In this post, I’m looking at network designs with ECMP cores using TRILL or SPB, I’m realising that STP is equally improved in terms of risk and performance by reducing the STP domain size which leads to better stability, reduced risk and impact mitigation


OpenFlow might lower CapEx while SDN will increase OpEx

A lot of people have talked extensively about OpenFlow making significant changes to the networking business. In particular, many writers have focussed on the possibility that OpenFlow enables a choice of using low cost network equipment instead of the expensive networking equipment that we use today.

Well, that’s highly unlikely.

Cisco ASA-CX – No Java

Just watched this video on the ASA-CX. Only one thing made my heart leap with joy. NO JAVA.

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