FEATURE DATA CENTRES
Combining networks seamlessly Cisco Systems has adopted a different philosophy for tackling network automation and scale. Its Application Centric Infrastructure (ACI) is being launched in two stages. Te first, a standalone phase, equips its Nexus switches with an interface to enable control using such tools as OpenFlow and Openstack. Openstack is an open-source cloud computing platform that controls servers, storage, and networking resources. Te second phase implements the full vision of
ACI. Here the platforms will implement Cisco’s fabric mode once it issues a soſtware upgrade. Cisco has developed a custom ASIC to implement what it calls a hierarchical policy model. Te policy layer sits above the control plane. Here Cisco has eschewed SDN, implementing ACI’s networking as a single system based on a distributed control plane that resides on all the platforms. ‘Our approach with ACI is how can we bring the
overlay and the physical network together to work in a seamless way,’ says Greg Page, technical solutions architect, data centre and virtualisation, EMEAR at Cisco. ‘How can we conjoin them to get the benefits of overlay – speed and flexibility of deployment – but also get the assurance of the underlay network: performance, speed, packets- per-second processing, security, and scale.’ Tese underlay-network benefits result from
using custom silicon, says Page. An ASIC delivers a tenfold packet-processing performance advantage compared to soſtware on a server’s general-purpose processor, and an even greater twentyfold power efficiency. Cisco’s ASIC performs the packet processing to enforce policy that determines which applications and which virtual machines can talk to each other and how. Having visibility into the physical network
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A diagramatic representation of the three main approaches described in this feature
Applications &
Hypervisors
l NVO gateway support for VMware & Microsoft
Dell Networking
Infrastructure controller & Physical Fabric
l Legacy Interoperability l Open Automation
Legacy Environments
brings operational benefits, says Page: ‘If I’ve deployed an overlay and I am losing packets, I don’t know where the problem is because I can’t correlate between the physical and the virtual.’ SDN and the OpenFlow protocol used to control
the data plane is a third approach being pursued to address networking’s shortfalls. Cisco’s standalone mode supports this, as do other vendors. HP, also supporting network virtualisation, is a proponent of SDN and OpenFlow.
Supporting three approaches Dell claims its solution supports network virtualisation, SDN and legacy/vendor-specific systems, and that they will play a role in the data
NETWORK DISAGGREGATION
Another important industry development is the disaggregation of networking hardware and software. Customers for the first time can choose the software and hardware they use for networking. Traditionally, customers have been locked in to a particular switch vendor that provides its own operating system. In January 2014, Dell teamed
up with Cumulus Networks that has developed a Linux
networking operating system. Cumulus’s operating system will now run on Dell’s top-of- rack switches. ‘We are the first large IT vendor that allows a choice of operating system,’ says Dell’s Joshipura. Dell points out that the
switch/Cumulus operating system combination suits a subset of the total market: web companies and banks that have large IT staff skilled in Linux. ‘Those guys want to treat the switch as a server,’
says Joshipura. IDC’s Casemore says leading web players operating hyperscale data centres like such commodity, white-box switches. ‘They know what they want in a switch, they know how to integrate and support it, and have the buying power to say: “I want it at this price”.’ Casemore views Dell’s
decision to back network disaggregation as a significant industry first.
l OpenFlow & Controller Interoperability
Greenfield & Cloud Environments
centre. ‘We are the only ones making sure that all three camps can be migrated to SDN,’ says Joshipura. ‘Customers should not be required to choose an approach.’ ‘Te market is not going to go from a fully
distributed routing control plane that has been built out to internet scale for the past decade to purely a controller model,’ adds Martin McNealis, senior director, EOS, cloud services and technical support at Arista Networks. ‘So where the market has got to is a hybrid model: for certain applications or virtualised instances you want a programmable controller but for a broad set of traffic users, you may want to use existing mechanisms.’ Meanwhile, all the equipment makers continue
to advance the underlying physical network. Brocade, whose platforms support VMware’s NSX, points out that the overlay approach does not necessarily address every requirement in the best way. For example, managing multiple workloads: ‘Is that best addressed by a quite complex overlay technology or a relatively simple underlay technique that is built into the infrastructure you have invested in?’ says Nick Williams, senior product manager, EMEA, data centre IP at Brocade. Te company’s virtual fabric uses protocols and hardware that extends VLAN’s limit to enable up to 16 million VLAN connections, giving its customers the choice of using its network implementation or network virtualisation. Another vendor, Plexxi, has developed a
switch architecture that adds optical networking to its switches to complement layer two and layer three networking. ‘You want to have a network that understands what the overlay network looks like,’
16 FIBRE SYSTEMS Issue 3 • Spring 2014 Northbound Southbound
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