Ivan has blogged about how he thinks Juniper QFabric works Speculation: This is How I Would Build a QFabric, while I agree in terms of the software elements ( at least, they look like good guesses to me), I would like to discuss more about the hardware:
There are three components in a QFabric kit list :
- Edge Switch
My understanding is that the Interconnect chassis is a simple Fat Clos tree silicon and the QF/Edge acts like a blade in chassis that performs all the forwarding lookups, traffic classification and backbone encapsulation. The QF/Director acts as a pure management plane only.
In this understanding, the uplinks between the QF/Edge switches and QF/Interconnect are effectively “backplane” connection and traffic on the uplinks is tagged / munged / processed into a form for forwarding across the Silicon Fabric that is in the InterConnect chassis, and most likely the software uses the software mechanisms that Ivan describes in his post. This is the same idea as the connections between line cards and the supervisor in a traditional switch chassis which use a frame/packet encapsulation devised to meet the platform requirements.
The QF/Interconnect has line cards that have low cost silicon for network interfaces and not much else (no Distributed Feature functions or local switching) , and a bunch of silicon switchesblades that provide a Fat Tree Clos switching fabric for forwarding plane for the entire QFabric
Aside from the fact that Juniper performs the forwarding decision is performed at the QF/Edge, it’s the same concept Cisco FabricExtenders (FEX) use by extending the backplane to external modules with a proprietary tagging scheme between the edge device and the core switch. The big difference is that the Cisco approach means that a “fat switch” with high capex (good for Cisco’s business) is needed to scale this, where the Juniper solution means that InterConnect is cheaper and the intelligent edge scales more effectively. Each purchase of an QF/Edge increases the forwarding performance of the entire system, and the funding process is better aligned to a private / public cloud revenue model. This is really vital to successful cloud deployments and causing major change in the storage industry as well.
This is the unit that was on display at Interop – its look huge, and it IS big but don’t be scared – but it’s the full size unit to show off to the press – there are quarter and half sized switching planes to be released in the near future.
So a couple of points about this unit that I’ve been told :
- just because it’s big, doesn’t mean it is expensive. I’m assured it’s simplicity means it’s low cost.
- there are smaller and cheaper versions than this (half and quarter size).
- because it is a simple silicon fabric, it’s essentially a dumb element when compared to existing approaches such as Brocade or Cisco
- it’s big to have enough ports for a large number of edge switches
- It needs a lot of air to keep that silicon cool – that’s part of the reason it is so large.
The EtherealMind View
I’ve approached Juniper to be on the Packet Pushers Podcast and talk about QFabric in detail – I think it would make a good show. However, their PR/marketing department appear to be scared of independent bloggers and social media and keep blowing me off. I’m still hopeful, but I’m not going to bother much longer.
I do think that the QFabric approach is different, up to a point. In the sense that they reinvented the wheel to make it better , the concept of using distributed edge switching is a old technical idea returning for another day in the sun 1. With developments in software and software development today, the problems of reliable coherence between all elements in the edge ( to allow distributed forwarding) is a practical problem, and the use of ISIS in the LAN seems have to gained acceptance in the marketplace.
So far, I think QFabric is well suited to the idea of Cloud networks because it provides greater overall flexibility, and a purchasing model that is better aligned to purchasing that the conventional Cisco/Brocade approach of buying all the performance in one big hit up front (which just so happens to be good for their bottom line and not yours).
I’ll be interested is seeing more information at it arrives.
- Networking Truth 11 – Every old idea will be proposed again with a different name and a different presentation, regardless of whether it works – http://etherealmind.com/twelve-networking-truths-rfc-9125/ ↩
Other Posts in A Series On The Same Topic
- ◎ What's Happening Inside an Ethernet Switch ? ( Or Network Switches for Virtualization People ) (11th January 2013)
- Tech Notes: Juniper QFabric - A Perspective on Scaling Up (14th February 2012)
- Switch Fabrics: Input and Output Queues and Buffers for a Switch Fabric (6th September 2011)
- Switch Fabrics: Fabric Arbitration and Buffers (22nd August 2011)
- What is an Ethernet Fabric ? (21st July 2011)
- What is the Definition of a Switch Fabric ? (30th June 2011)
- Juniper QFabric - My Speculations (1st June 2011)