A series of posts on Silicon Switching and the internal of switch chips and fabrics.

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

vxlan-stt-switch-silicon-2

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 ?

Tech Notes: Juniper QFabric – A Perspective on Scaling Up

qfabric-depth-3.jpg

Juniper QFabric is a new approach to Ethernet Switch Fabrics. When it was announced last year,it was noted that the underlying physical design is a completely different approach to building Switch Fabrics. Here I’m taking a loosely research based approach to understand how Juniper QFabric is different from all other approaches to the problem, and also a look at some of the challenges ahead.

Switch Fabrics: Input and Output Queues and Buffers for a Switch Fabric

Now that this has established that a Switch Fabric has buffers, I want to flip back into something practical about this application. Lets use an example of four servers connecting to single switch and sharing an Ethernet Storage Array. The array might be using iSCSI or FCoE to delivery SCSI applications to the Servers. The nature of storage traffic is such that it has transient spikes in traffic that must maintain low latency and should not be dropped.

Switch Fabrics: Fabric Arbitration and Buffers

In the article, “What Is the Definition of a Switch Fabric ?” on Switch Fabrics I looked at how a Crossbar switching fabric allow for concurrent circuit forwarding and how this is used to build a fabric. In most cases, frames would be received and forwarded from an input to an output, as show in […]

What is the Definition of a Switch Fabric ?

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.