Juniper Networks has two advanced top-of-rack switches in its data center network portfolio today: the QFX3500...
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and the EX4550. Each switch is part of a separate product family. To decide which switch is right for your data center is to choose between two starkly different network architectures and strategies.
Two Juniper data center network architectures
Enterprises have two paths they can follow when building a data center network with Juniper. Customers can either build a traditional two- or three-tiered network, or they can build a data center fabric with Juniper's QFabric technology.
Juniper's EX switches and its MX routers are the basic building blocks for a traditional data center network, and the EX4550 is the newest addition. Released this fall, the EX4550 is Juniper's next-generation top-of-rack EX switch, following in the footsteps of the EX4200 and EX4500.
The QFX3500 is part of QFabric, Juniper's new architecture for data center networking. With QFabric, an enterprise can operate an entire data center network as a giant modular switch. The QFX3500 serves as a node within that architecture and functions like a line card on a modular chassis. Juniper offers two other classes of devices to complete the architecture. The QFabric Interconnect is a large chassis device that functions as the switching backplane and connects multiple QFX3500s into a full-mesh topology. QFabric Director is an out-of-band control-and-management plane device. In QFabric, the QFX3500 serves as either the top-of-rack or end-of-row device and enables any-to-any server connectivity across a data center.
Enterprises can, however, also deploy the QFX3500 as a top-of-rack switch in a traditional data center network, forcing enterprises to take a closer look at both products and both architectures before investing.
Comparing top-of-rack switches: The EX4550
The EX4550 is a traditional top-of-rack switch. It ships with 32 fixed, 10 Gigabit Ethernet (GbE) ports, either fiber SFP/SFP+ or copper 100M/1GBASE-T/10GBASE-T. The switch also has front and back expansion slots, for which Juniper offers 8 x 10 GbE modules that can push the switch's density up to 48 ports. The 32-port switch's starting list price is $19,000.
The expansion slots on the EX4550 can also accommodate a Virtual Chassis module, which has two 128 Gbps interconnect ports. These modules enable Juniper's Virtual Chassis capability, a more advanced and feature-rich alternative to traditional switch stacking. Juniper says the control and data planes in a Virtual Chassis configuration are more sophisticated than a simple switch stack, enabling multiple Juniper switches to operate together as a modular switch. In a data center server edge scenario, the Virtual Chassis feature enables simpler management.
The EX4550, Juniper's next-generation improvement on the EX4500, is smaller (one rack unit versus two) but with the same port density. It's also faster; the EX4500 averages 4 to 5 microseconds of latency while the EX4550 averages around 2 microseconds. The total stacked bandwidth of an EX4550 is also double that of a stack of EX4500s: from 128 Gbps to 256 Gbps. Customers have the option of combining both models in a single Virtual Chassis along with Juniper's older EX4200 switches.
The EX4550 is 40 GbE-ready, and Juniper plans to sell 40 GbE uplink modules, although the company hasn't indicated when they will be available. The EX switch family doesn't include 40 GbE-ready modular switches for data centers. However, Juniper customers who need a core data center device that can aggregate 40 GbE uplinks can use Juniper's MX series routers, said Dhritiman Dasgupta, senior director for product marketing at Juniper. Juniper wouldn't comment on if or when it will offer 40 GbE support in its data center-class modular switch series, the EX8200.
Comparing top-of-rack switches: The QFX3500
Like the EX4550, the QFX3500 is a one-rack unit device. It ships with 48 dual-mode SFP+ ports and four QSFP+ ports, enabling 63 x 10 GbE ports. It will support 4 x 40 GbE ports in the future. The switch's list price is $34,000.
The QFX3500 is simply more robust than its EX counterpart. It offers submicrosecond latency, according to Juniper. It also has a much larger MAC address -- 120,000 addresses versus the 32,000 available on the EX4550. It has a data rate of 960 million packets per second (Mpps) versus the EX4550's 714 Mpps. It has a total throughput rate of 1.28 Tbps versus the EX4550's 960 Gbps.
The QFX3500 is also distinguished by its ability to terminate native Fibre Channel and convert storage traffic over to Fibre Channel over Ethernet, or vice versa.
Choosing either the QFX3500 or the EX4550
A network engineer will need to consider both present and future needs when deciding whether to select the EX4550 or the QFX3500. At the outset, the QFX3500 offers more in terms of speeds and feeds and is clearly designed strictly for the data center.
More on Juniper switching
Integrating QFabric into your existing data center network
Juniper shrinks QFabric to meet midsized customers
Virtual cluster switching: Finding management in a flat network
Network Innovation Award: Juniper QFabric
If an enterprise is considering a possible migration to Juniper's QFabric architecture, the QFX3500 is the ideal choice. Network engineers can deploy it now as a top-of-rack device in a traditional network and leave the switches in place when the migration to the QFabric happens.
If an enterprise's mid- to long-term plans are focused simply on upgrading from Gigabit Ethernet to 10 GbE in the data center, the EXC4550 is the better choice.
The EX4550 is also useful as a campus network core-and-aggregation device. A stack of EX 4550s in Virtual Chassis configuration could replace a more traditional modular campus switch, such as the Catalyst 6500. Juniper offers MPLS support on the switch specifically for this kind of deployment. Given its applicability in a campus network, an enterprise could repurpose EX4550s from the data center to the campus during a future refresh cycle. Juniper, meanwhile, has no plans today to offer MPLS on the QFX3500. That switch is strictly a data center-class server access switch.
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