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RETHINKING THE DATA CENTER NETWORK Sponsored by

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Design to the Core

While almost every part of a modern data center can be con-

sidered mission critical, the network is the absolute founda-

tion of all communications. Thats why it must be designed

and built right the rst time. After all, the best servers and

storage in the world cant do anything without a solid network.

To that end, here are a variety of design points and

best practices to help tighten up the bottom end.

Core considerations

The term network applies to everything from LAN to SAN

to WAN. All these variations require a network core, so

lets start there.

The size of the organization will determine the size and ca-

pacity of the core. In most infrastructures, the data center core

is constructed differently from the LAN core. If we take a hypo-

thetical network that has to serve the needs of a few hundred

or a thousand users in a single building, with a data center

in the middle, its not uncommon to nd that there are big

switches in the middle and aggregation switches at the edges.

Ideally, the core is composed of two modular switching

platforms that carry data from the edge over gigabit ber,

located in the same room as the ser ver and storage infra-

structure. Two gigabit ber links to a closet of, say, 100

switch ports is sufcient for most business purposes. In

the event that its not, youre likely better of f bonding mul-

tiple 1Gbit links rather than upgrading to 10G for those

closets. As 10G drops in price, this will change, but for

now, its far cheaper to bond several 1Gbit ports than to

add 10G capability to both the core and the edge.

In the likely event that VoIP will be deployed, it may be bene-

cial to implement small modular switches at the edge as well,

allowing Power over Ethernet (PoE) modules to be installed in

the same switch as the non-PoE por ts. Alternatively, deploying

trunked PoE ports to each user is also a possibility. This allows

a single port to be used for VoIP and desktop access tasks.

In the familiar hub-and-spoke model, the core connects

to the edge aggregation switches with at least two links,

either connecting to the server infrastructure with direct

copper runs or through server aggregation switches in

each rack. This decision must be determined site by site,

By Paul Venezia InfoWorld

A networking primer on the fundamentals, from the rightswitches to the right network monitoring techniques

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due to the distance limitations of copper cabling.

Either way, its cleaner to deploy server aggregation

switches in each rack and run only a few ber links back

to the core than try to shoehorn everything into a few huge

switches. In addition, using server aggregation switches will

allow redundant connections to redundant cores, which will

eliminate the possibility of losing server communications in

the event of a core switch failure. If you can afford it and

your layout permits it, use server aggregation switches.

Regardless of the physical layout method, the core switches

need to be redundant in every possible way: redundant power,

redundant interconnections, and redundant routing protocols.

Ideally, they should have redundant control modules as well,

but you can make do without them if you cant afford them.

Core switches will be responsible for switching nearly

every packet in the infrastructure, so they need to be bal-

anced accordingly. Its a good idea to make ample use of

Hot Standby Routing Protocol (HSRP) or Virtual Routing

Redundancy Protocol (VRRP). These allow two discrete

switches to effectively share a single IP and MAC address,

which is used as the default route for a VLAN. In the event

that one core fails, those VLANs will still be accessible.

Finally, proper use of Spanning-Tree Protocol (STP) is

essential to proper network operation. A full discussion of

these two technologies is beyond the scope of this guide,

but correct conguration of these two elements will have a

signicant effect on the resiliency and proper operation of

any Layer-3 switched network.

Minding the storage

Once the core has been built, you can take on storage net-

working. Although other technologies are available, when

you link servers to storage arrays, your practical choice will

probably boil down to a familiar one: Fibre Channel or iSCSI?

Fibre Channel is generally faster and delivers lower laten-

cy than iSCSI, but its not truly necessary for most applica-

tions. Fibre Channel requires specic FC switches and costly

FC HBAs in each server ideally two for redundancy

while iSCSI can perform quite well with standard gigabit

copper ports. If you have transaction-oriented applica-

tions such as large databases with thousands of users,

you can probably choose iSCSI without affecting perfor-

mance and save a bundle.

Fibre Channel networks are unrelated to the rest of the

network. They exist all on their own, linked only to the

main network via management links that do not carry any

transactional trafc. iSCSI networks can be built using

the same Ethernet switches that handle normal network

trafc although iSCSI networks should be conned into

their own VLAN at the least, and possibly built on a spe-

cic set of Ethernet switches that separate this trafc for

performance reasons.

Make sure to choose the switches used for an iSCSI

storage network carefully. Some vendors sell switches

that perform well with a normal network load but bog

down with iSCSI trafc due to the internal s tructure of the

switch itself. Generally, if a switch claims to be enhanced

for iSCSI, it will perform well with an iSCSI load.

Either way, your storage network should mirror the main

network and be as redundant as possible: redundant

switches and redundant links from the servers (whether

FC HBAs, standard Ethernet ports, or iSCSI accelerators).

Servers do not appreciate having their storage suddenly

disappear, so redundancy here is at least as important as

it is for the network at large.

Going virtual

Speaking of storage networking, youre going to need some

form of it if you plan on running enterprise-level virtualiza-
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tion. The ability for virtualization hosts to migrate virtual

servers across a virtualization farm absolutely requires sta-

ble and fast central storage. This can be FC, iSCSI, or even

NFS in most cases, but the key is that all the host servers

can access a reliable central s torage network.

Networking virtualization hosts isnt like networking

a normal server, however. While a server might have a

front-end and a back-end link, a virtualization host might

have six or more Ethernet interfaces. One reason is per-

formance: A virtualization host pushes more trafc than a

normal server due to the simple fact that as many as doz-

ens of virtual machines are running on a single host. The

other reason is redundancy: With so many VMs on one

physical machine, you dont want one failed NIC to take a

whole bunch of virtual servers ofine at once.

To combat this problem, virtualization hosts should

be constructed with at least two dedicated front-end

links, two back-end links, and, ideally, a single manage-

ment link. If this infrastructure will service hosts that live

in semi-secure networks (such as a DMZ), then it may

be reasonable to add physical links for those networks

as well, unless youre comfortable passing semi-trusted

packets through the core as a VLAN. Physical separation

is still the safest bet and less prone to human error. If you

can physically separate that trafc by adding interfaces to

the virtualization hosts, then do so.

Each pair of interfaces should be bonded using some

form of link aggregation, such as Link Aggregation Control

Protocol (LACP) or 802.3ad. Either should sufce, though

your switch may support only one form or the other. Bond-

ing these links establishes load-balancing as well as

failover protection at the link level and is an absolute re-

quirement, especially since youd be hard-pressed to nd

a switch that doesnt support it.

In addition to bonding these links, the front-end bundle

should be trunked with 802.1q. This allows multiple VLANs

to exist on a single logical interface and makes deploying

and managing virtualization farms signicantly simpler. You

can then deploy virtual servers on any VLAN or mix of VLANs

on any host without worrying about virtual interface congu-

ration. You also dont need to add physical inter faces to the

hosts just to connect to a different VLAN.

The virtualization host storage links dont necessarily

need to be either bonded or trunked unless your virtual

servers will be communicating with a variety of back-end

storage arrays. In most cases, a single storage array will

be used, and bonding these inter faces will not necessarily

result in performance improvements on a per-server basis.

However, if you require signicant back-end ser ver-to-serv-

er communication, such as front-end Web servers and back-

end database servers, its advisable to dedicate that trafc

to a specic set of bonded links. They will likely not need to

be trunked, but bonding those links will again provide load-

balancing and redundancy on a host-by-host basis.

While a dedicated management interface isnt truly a

requirement, it can certainly make managing virtualization

hosts far simpler, especially when modifying network pa-

rameters. Modifying links that also carr y the management

trafc can easily result in a loss of communication to the

virtualization host.

So if youre keeping count, you can see how you might

have seven or more interfaces in a busy virtualization host.

Obviously, this increases the number of switch ports required

for a vir tualization implementation, so plan accordingly. The

increasing popularity of 10G networking and the dropping

cost of 10G interfaces may enable you to drastically re-

duce the cabling requirements so that you can simply use a

pair of trunked and bonded 10G interfaces per host with a

management interface. If you can afford it, do it.


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Design to the Core

FOUR TRENDS SHAPE THE NEW DATA CENTERBy Beth Schultz Network World

IT execs adapt to a new reality as x86 virtualization transforms the data center forever

Thanks to x86 server virtualization and its follow-on tech-

nologies, the state-of-the-art enterprise data center looks

vastly different than it did even a year ago.

And moving from old school to next-generation isnt just

about hardware and software its a call for a new way of

thinking about the data center, as well.

Some people are so accustomed to one application,

one server and a methodology that locks you in to one

way of thinking that theyre having a hard time fully under-

standing the new data center, says Bill Fife, director of

technology for Wholesale Electric Supply Co., in Houston.

But now with thin replication and replays and synchro-

nization to disaster recovery sites, and virtual machines

being able to move les from data store to data store and

having multiple data stores on the server, and adding net-

work adapters, you really have to sit back and think about

how you want to run your operations and remember that

you have options. Youre not tied down to any one path.

You can go down one road today and change directions

tomorrow, Fife says.

Here are four of the major trends in todays data center:

TREND NO. 1: I/O virtualization

At Wholesale Electric Supply, Fife is capitalizing on the

ability to virtualize I/O, one of the latest of several signi-

cant technology trends shaping the new data center.

I/O virtualization, also known as I/O aggregation, splits

interconnections across either 10-gigabit InniBand or

Ethernet links. Xsigo Systems virtual I/O Director uses the

former and Ciscos Nexus 5000 and 7000 switches the

latter, for example.

In either case, you connect this pipe and then you can

get as many virtual Ethernet and Fibre Channel connec-

tions as you want out of it, says Logan Harbaugh, an in-

dependent analyst and member of the Network World Lab

Alliance. The architectures are similar, as theres a limit

to how much they can vary and still provide some level of

functionality.

I/O virtualization simplies the hardware scenario in

the data center rather considerably, reducing the number

of connections running to each device while increasing

exibility. Take into consideration VMwares best practices

recommendation that you assign a 1G port per vir tual ma-

chine (VM). With newer 24-core servers, you could theo-

retically run at least 24 and maybe as many as 50 VMs

on a single piece of hardware, which in turn would mean

needing 50 1G ports, Harbaugh says.

Realistically, even if you could get six four-port Ether-


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net boards, youd still only be able to support 24 VMs.

The nice thing about I/O virtualization is that everything

shares the one InniBand or 10G Ethernet connection as

lots of 1G pipes.

At Wholesale Electric, Fife is using Xsigos virtual I/O

Director to decouple processing, storage and I/O. By do-

ing so weve essentially built our own cloud because we

can assign processor, RAM, disk and I/O on an as-needed

basis, and then, when theyre no longer needed, get rid of

it all and do something else, he says. There are no rigid

guidelines within which we have to operate. We can be

extremely exible.

TREND NO. 2:

Data and storage convergence

Todays data centers typically have distinct data and stor-

age networks, and nobody much likes that situation. As

soon as people can recombine those two networks, thats

what theyre going to do, says Joel Snyder, senior partner

with consulting rm Opus One and another member of the

Network World Lab Alliance.

My belief and, yes, hope is that well get rid of pure Fi-

bre Channel and go to Fibre Channel over Ethernet [FCoE]

but I still see people buying a lot of Fibre Channel be-

cause theyre told its the way to go, even though our tests

actually show that the network of ten isnt the bottleneck,

he says. What you can do with Fibre Channel you can

do with 10G Ethernet and get equivalent or better per-

formance, even if thats not the belief of SAN buyers and

vendors.

This is early days for FCoE, but plenty of folks are look-

ing at the technology, says David Newman, president

of Network Test, an independent test rm, and Network

World Lab Alliance member. If nothing more, the technol-

ogy has cost in its favor, he says.

Besides the capital cost of the equipment, theres

the operational expense issue. People who run plain old

Ethernet cost less than people who know Fibre Channel,

Newman says. On economic grounds, itll be cheaper to

provision FCoE than running separate infrastructures.

Today, Brocade and Cisco have FCoE-capable switches

that fully support all prioritizations and new mechanisms

on Ethernet for delivering Fibre Channel-like service levels,

and other vendors are coming into the fray, as well. So

building a working, end-to-end FCoE network that handles

data and storage is possible today at least using the

same vendors gear, Newman says. Interoperability is un-

proven as yet.

Scott Engel, director of IT infrastructure, Transplace,

a third-party logistics provider in Dallas, identies FCoE

as one of the two biggest networking and infrastructure

changes coming to the companys data center over the

next year. The other is 10G to the servers, he says.

Indeed, Newman says, the real tipping point in the

data center will happen over the next 12 to 18 months

when 10G replaces 1G Ethernet on server motherboards.

Thatll have all sorts of follow-on effects, enabling data-

storage convergence is just one, he says.

Watch for this year to be the rst with appreciable

numbers of 40G switch ports shipping, Newman says.

Fatter network pipes will be needed to accommodate the

higher-speed server connections.

TREND NO. 3:

Faster processors, greater consolidation

By now, most enterprises have server consolidation sto-

ries to share, spun around a virtualization theme. They tell

of impressive physical-to-virtual server ratios, often in the

double digits. But consolidation in the data center is just


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beginning, some say.

The maturity and comfort levels around virtualization

are growing, which means enterprises are showing the

willingness to put more and more VMs on a single system,

says Steve Sibley, an IBM Power Systems manager. Within

the year, he adds, the Power 750 will support up to 320

VMs on a single ser ver, the Power 770 and 780 up to 640

VMs and plans for up 1,000 VMs.

The ability to support higher numbers of VMs per phys-

ical server comes on the back of faster processors, of

course. In IBMs case, the company recently introduced

the Power7, an eight-core chip that delivers four times

the virtualization capability, scalability and performance

than its predecessor, Sibley says. The high-end Power7-

based Power 780 and 770 servers will come with up to

64 Power7 cores, for example.

Intel, too, is readying an eight-core chip, code-named

Nehalem-EX. That chip is expected out by mid-year.

If you start at the chip level, the ability to deliver more

performance per processor core but also pack four times

as many cores onto a single chip gives a vast amount of

new capacity and capability to put more virtual servers

onto a single platform without sacricing performance or

capability of the overall system, Sibley says. That design

point is enabling systems or offerings that give clients the

ability to consolidate even more than they used to on a

single platform at much cheaper prices than ever before.

TREND 4: Infrastructure optimization

Will your data center strategy one day include a semi

tractor-trailer full of hands-off gear parked in some spot

selected for optimal cooling and power supply?

Dan Kusnetzky, vice president of research operations

at The 451 Group, says he can imagine so at least as

one potential alternative to building out new or extending

existing data centers. Software routes around failures,

and maybe youd replace that truck with a new one every

three years or so, he says.

The data center-in-a-box concept is one that bears

watching, agrees Doug Oathout, vice president of con-

verged infrastructure at HP. Companies already are using

data centers like pods or trailers outside their facilities,

optimizing server, storage, networking, cooling and power

distribution resources for that size container, he says.

Now we see the performance-optimization trend moving

inside the data center.

This is not to say the data center is going to turn into

parking lot full of semis. But enterprises that run out of

space, electricity, cooling and capacity today can take the

container concept and move that type of asset inside the

data center, Oathout says. Were not talking about the

Were not talking about the container itself, but the concept, being able to say I need

eight racks of servers, four racks of storage, a rack and half of networking, and heres thepower and cooling it will consume, and optimize that way.

Doug Oathout, vice president of converged infrastructure, HP

ITS THE INSIDETHAT MATTERS


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container itself, but the concept, being able to say I need

eight racks of servers, four racks of storage, a rack and

half of networking, and heres the power and cooling it will

consume, and optimize that way.

Piecing together a data center section by section is

far less costly than the traditional go-for-broke approach,

and delivering power and cooling a section at a time is

far more efcient than moving it across a long distance,

Oathout says.

Theres so much more waste when you build a data

center to the ultimate capacity vs. building it to what it

needs to do, so you could almost call this a retrotting

trend, Oathout adds. Im going to optimize what Ive got,

doing it with localized power, cooling and energy for the

specic work I want to get done in this environment. Then

I take the next step, with multiple pods, instantiations or

building blocks within the data center. Its mindboggling

how much more efcient that is compared to building a

monolithic data center that has mega watts and 100,000

square feet of space yet is incapable of supporting the

equipment you need for your next workload.

Schultz is a freelance IT writer in Chicago. You can reach

her [email protected].


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EMERGING IEEE ETHERNET STANDARDS

COULD SOOTHE DATA CENTER HEADACHES

Even as Cisco, HP and others are increasingly invading

each others turf in the data center, they are also joining

forces to push through new Ethernet standards that could

greatly ease management of those increasingly virtualized

IT nerve centers.

The IEEE 802.1Qbg and 802.1Qbh specications are de-

signed to address serious management issues raised by the

explosion of virtual machines in data centers t hat tradition-

ally have been the purview of physical servers and switches.

In a nutshell, the emerging standards would ofoad signi-

cant amounts of policy, security and management process-

ing from virtual switches on network interface cards (NIC)

and blade servers and put it back onto physical Ethernet

switches connecting storage and compute resources.

The IEEE draft standards boast a feature called Virtual

Ethernet Port Aggregation (VEPA), an extension to physi-

cal and virtual switching designed to eliminate the large

number of switching elements that need to be managed

in a data center. Adoption of the specs would make man-

agement easier for server and network administrators by

requiring fewer elements to manage, and fewer instances

of element characteristics such as switch address ta-

bles, security and service attribute policies, and congu-

rations to manage.

There needed to be a way to communicate between the

hypervisor and the network, says Jon Oltsik, an analyst

at Enterprise Systems Group. When you start thinking

about the complexities associated with running dozens of

VMs on a physical server the sophistication of data center

switching has to be there.

But adding this intelligence to the hypervisor or host would

add a signicant amount of network processing overhead

to the server, Oltsik says. It would also duplicate the task

of managing media access control address tables, aligning

policies and lters to ports and/or VMs and so forth.

If switches already have all this intelligence in them, why

would we want to do this in a different place? Oltsik notes.

VEPA does its part by allowing a physical end station

to collaborate with an external switch to provide bridging

support between multiple virtual end stations and VMs,

By Jim Duffy Network World

Under development is a way to ofoad policy, security and management

processing from virtual switches


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and external networks. This would alleviate the need for

virtual switches on blade servers to store and process ev-

ery feature such as security, policy and access control

lists (ACLs) resident on the external data center switch.

Diving into IEEE draft standard details

Together, the 802.1Qbg and bh specications are de-

signed to extend the capabilities of switches and end sta-

tion NICs in a vir tual data center, especially with the pro-

liferation and movement of VMs. Citing data from Gartner,

ofcials involved in the IEEEs work on bg and bh say 50%

of all data center workloads will be virtualized by 2012.

Some of the other vendors involved in the bg and bh

work include 3Com (now HP), Blade Network Technolo-

gies, Brocade, Dell, Extreme Networks, IBM, Intel, Juni-

per Networks and QLogic. While not the rst IEEE speci-

cations to address virtual data centers, bg and bh are

amendments to the IEEE 802.1Q specication for virtual

LANs and are under the purview of the organizations

802.1 Data Center Bridging and Interworking task groups.

The bg and bh standards are expected to be ratied

around mid-2011, according to those involved in the IEEE

effort, but pre-standard products could emerge in late

2010. Specically, bg addresses edge vir tual bridging: an

environment where a physical end station contains mul-

tiple virtual end stations participating in a bridged LAN.

VEPA allows an external bridge or switch to perform

inter-VM hairpin forwarding of frames, something stan-

dard 802.1Q bridges or switches are not designed to do.

GETTING VIRTUALIZED DATA CENTERS UNDER CONTROLThe IEEEs emerging 802.1Q bg and bh standards are designed to address manageability of the growing population of

virtual machines in data centers. They are intended to better align the capabilities of physical Ethernet switches in the edge andcore of data center networks with virtual switches in the server so that operations and management of these elements does

not overwhelm server and network administrators. Heres a look at key capabilities of the emerging standards:

Virtual Ethernet PortAggregation (VEPA)

Multichannel Remote Replication

VM VMVM VMVM VM

Switch Switch Switch

Enables VMs to use external switch to

access features such as ACLs, policies,VLAN assignments, security, etc. Allows

hairpin turns on same switch port for

inter-VM communications.

Creates virtual switch ports for

simultaneous switching of trafc frommultiple VMs. Adjacent switches use

tags to replicate frames for multicast

applications.

Denes a new tag format and uses

port extenders for replicating packetsto a remote switch for control and

feature access/assignment.

Server Server Port Port Port

Port Extender

VM VMVM VMVM VM


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On a bridge, if the port it needs to send a frame on

is the same it came in on, normally a switch will drop

that packet, says Paul Congdon, CTO at HP ProCurve, vice

chair of the IEEE 802.1 group and a VEPA author. But

VEPA enables a hairpin mode to allow the frame to be

forwarded out the port it came in on. It allows it to turn

around and go back.

VEPA does not modify the Ethernet frame format but

only the forwarding behavior of switches, Congdon says.

But VEPA by itself was limited in its capabilities. So HP

combined its VEPA proposal with a Ciscos VN-Tag pro-

posal for server/switch forwarding, management and

administration to support the ability to run multiple vir-

tual switches and multiple VEPAs simultaneously on the

endpoint.

This required a channeling scheme for bg, which is

based on the VN-Tag specication created by Cisco and

VMware to have a policy follow a VM as it moves. This

multichannel capability attaches a tag to the frame that

identies which VM the frame came in on.

But another extension was required to allow users to

deploy remote switches instead of those adjacent to

the server rack as the policy controlling switches for the

virtual environment. This is where 802.1Qbh comes in: It

allows edge virtual bridges to replicate frames over mul-

tiple virtual channels to a group of remote ports. This will

enable users to cascade ports for exible network design,

and make more efcient use of bandwidth for multicast,

broadcast and unicast frames.

The port extension capability of bh lets administrators

choose the switch they want to delegate policies, ACLs,

lters, QoS and other parameters to VMs. Port extenders

will reside in the back of a blade rack or on individual

blades and act as a line card of the controlling switch,

says Joe Pelissier, technical lead at Cisco.

It greatly reduces the number of things you have to

manage and simplies management because the control-

ling switch is doing all of the work, Pelissier says.

Cisco, HP say theyre in synch

Whats still missing from bg and bh is a discovery protocol

for autoconguration, Pelissier says. Some in the 802.1

group are leaning toward using the existing Logical Link

Discovery Protocol (LLDP), while others, including Cisco

and HP, are inclined to dene a new protocol for the task.

LLDP is limited in the amount of data it can carry and

how quickly it can carry that data, Pelissier says. We

need something that carries data in the range of 10s

to 100s of kilobytes and is able to send the data faster

rather than one 1,500 byte frame a second. LLDP doesnt

have fragmentation capability either. We want to have the

Cisco and HP are leading proponents of the IEEE effort despite the fact that

Cisco is charging hard into HPs traditional server territory while HP is ramping

up its networking efforts ....OF LIKE MINDS


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capability to split the data among multiple frames.

Cisco and HP are leading proponents of the IEEE effort

despite the fact that Cisco is charging hard into HPs tradi-

tional server territory while HP is ramping up its networking

efforts in an attempt to gain control of data centers that have

been turned on their heads by vir tualization technology.

Cisco and HP say their VEPA and VN-Tag/multichannel

and port extension proposals are complementary despite

reports that they are competing techniques to accomplish

the same thing: reducing the number of managed data

center elements and dening a clear line of demarcation

between NIC, server and switch administrators when mon-

itoring VM communications.

This isnt the battle its been made out to be, Pelissier says.

Though Congdon acknowledges he initially proposed

VEPA as an alternative to Ciscos VN-Tag technique, the

two together present a nice layered architecture that

builds upon one another where virtual switches and

VEPA form the lowest layer of implementation, and you

can move all the way to more complex solutions such as

Ciscos VN-Tag.

And the proposals seem to have broad industry support.

We do believe this is the right way to go, says Dhriti-

man Dasgupta, senior manager of data center marketing

at Juniper. This is putting networking where it belongs,

which is on networking devices. The network needs to

know whats going on.


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10G ETHERNET SHAKES NET DESIGN TO THE CORE

Shift from three- to two-tier architectures driven by need for speed, server

virtualization, unied switching fabrics

The emergence of 10 Gigabit Ethernet, virtualization and

unied switching fabrics is ushering in a major shift in

data center network design: three-tier switching architec-

tures are being collapsed into two-tier ones.

Higher, non-blocking throughput from 10G Ethernet

switches allows users to connect server racks and top-of-

rack switches directly to the core network, obviating the

need for an aggregation layer. Also, server vir tualization is

putting more application load on fewer servers due to the

ability to decouple applications and operating systems

from physical hardware.

More application load on less server hardware requires

a higher-performance network.

Moreover, the migration to a unied fabric that con-

verges storage protocols onto Ethernet also requires a

very low-latency, lossless architecture that lends itself to a

two-tier approach. Storage trafc cannot tolerate the buff-

ering and latency of extra switch hops through a three-tier

architecture that includes a layer of aggregation switch-

ing, industry experts say.

All of this necessitates a new breed of high-performance,

low-latency, non-blocking 10G Ethernet switches now hitting

the market. And it wont be long before these 10G switches

are upgraded to 40G and 100G Ethernet switches now that

the IEEE has ratied those standards.

Over the next few years, the old switching equipment

needs to be replaced with faster and more exible switch-

es, says Robin Layland of Layland Consulting, an adviser

to IT users and vendors. This time, speed needs to be

coupled with lower latency, abandoning spanning tree

and support for the new storage protocols. Networking in

the data center must evolve to a unied switching fabric.

A three-tier architecture of access, aggregation and

core switches has been common in enterprise networks

for the past decade or so. Desktops, printers, servers and

LAN-attached devices are connected to access switches,

which are then collected into aggregation switches to

manage ows and building wiring.

Aggregation switches then connect to core routers/

switches that provide routing, connectivity to wide-area

network services, segmentation and congestion man-

agement. Legacy three-tier architectures naturally have

a large Cisco component specically, the 10-year-old

Catalyst 6500 switch given the companys dominance

in enterprise and data center switching.

Cisco says a three-tier approach is optimal for segmen-

By Jim Duffy Network World


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tation and scale. But the company also supports two-tier

architectures should customers demand it.

We are offering both, says Senior Product Manager

Thomas Scheibe. It boils down to what the customer

tries to achieve in the network. Each tier adds another two

hops, which adds latency; on the ipside it comes down to

what domain size you want and how big of a switch fabric

you have in your aggregation layer. If the customer wants

to have 1,000 10G ports aggregated, you need a two-tier

design big enough to do that. If you dont, you need an-

other tier to do that.

Blade Network Technology agrees: Two-tier vs. three-

tier is in large part driven by scale, says Dan Tuchler, vice

president of strategy and product management at Blade

Network Technologies, a maker of blade server switches

for the data center. At a certain scale you need to start

adding tiers to add aggregation.

But the latency inherent in a three-tier approach is inade-

quate for new data center and cloud computing environments

that incorporate server virtualization and unied switching

fabrics that converge LAN and storage trafc, experts say.

Applications such as storage connectivity, high-perfor-

mance computing, video, extreme Web 2.0 volumes and the

like require unique network attributes, according to Nick Lip-

pis, an adviser to network equipment buyers, suppliers and

service providers. Network performance has to be non-block-

ing, highly reliable and faultless with low and predictable la-

tency for broadcast, multicast and unicast trafc types.

New applications are demanding predictable perfor-

FORK IN THE ROADVirtualization, inexpensive 10G links and unied Ethernet switching fabrics are catalyzing a migration from three-tier Layer 3data center switching architectures to atter two-tier Layer 2 designs, which subsume the aggregation layer into the access

layer. Proponents say this will decrease cost, optimize operational efciency and simplify management.

Three tier Two tier Core

Core

Aggregation

Access Access/Aggregation

G C O


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mance and latency, says Jayshree Ullal, CEO of Arista

Networks, a privately held maker of low-latency 10G Eth-

ernet top-of-rack switches for the data center. Thats

why the legacy three-tier model doesnt work. Most of the

switches are 10:1, 50:1 oversubscribed, meaning dif-

ferent applications are contending for limited bandwidth

which can degrade response time.

This oversubscription plays a role in the latency of to-

days switches in a three-tier data center architecture,

which is 50 to 100 microseconds for an application re-

quest across the network, Layland says. Cloud and virtual-

ized data center computing with a unied switching fabric

requires less than 10 microseconds of latency to function

properly, he says.

Part of that requires eliminating the aggregation tier in a

data center network, Layland says. But the switches themselves

must use less packet buffering and oversubscription, he says.

Most current switches are store-and-forward devices

that store data in large buffer queues and then forward it

to the destination when it reaches the top of the queue.

The result of all the queues is that it can take 80 micro-

seconds or more to cross a three-tier data center, he says.

New data centers require cut-through switching which

is not a new concept to signicantly reduce or even

eliminate buffering within the switch, Layland says. Cut-

through switches can reduce switch-to-switch latency from

15 to 50 microseconds to 2 to 4, he says.

Another factor negating the three-tier approach to data

center switching is ser ver virtualization. Adding virtualization

to blade or rack-mount servers means that the ser vers them-

selves take on the role of access switching in the network.

Virtual switching inside servers takes place in a hyper-

visor and in other cases the network fabric is stretched to

the rack level using fabric extenders. The result is that the

access switching layer has been subsumed into the ser v-

ers themselves, Lippis notes.

In this model there is no third tier where trafc has

to ow to accommodate server-to-server ows; trafc is

either switched at access or in the core at less than 10

microseconds, he says.

Because of increased I/O associated with virtual

switching in the server there is no room for a blocking

switch in between the access and the core, says Asaf

Somekh, vice president of marketing for Voltaire, a maker

of Inniband and Ethernet switches for the data center.

Its problematic to have so many layers.

Another requirement of new data center switches is to

eliminate the Ethernet spanning tree algorithm, Layland

says. Currently all Layer 2 switches determine the best

path from one endpoint to another using the spanning

tree algorithm.

New data centers require cut-through switching which is not a new concept to

signicantly reduce or even eliminate buffering within the switch. Cut-throughswitches can reduce switch-to-switch latency from 15 to 50 microseconds to 2 to 4.

Robin Layland, principal, Layland Consulting

THE OLDSWITCHEROO

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Only one path is active, the other paths through the fab-

ric to the destination are only used if the best path fails. The

lossless, low-latency requirements of unied fabrics in virtu-

alized data centers requires switches using multiple paths

to get trafc to its destination, Layland says. These switches

continually monitor potential congestion points and pick the

fastest and best path at the time the packet is being sent.

Spanning tree has worked well since the beginning

of Layer 2 networking but the only one path [approach]

is not good enough in a non-queuing and non-discarding

world, Layland says.

Finally, cost is a key factor in driving two-tier architec-

tures. Ten gigabit Ethernet ports are inexpensive about

$500, or twice that of Gigabit Ethernet ports yet with 10

times the bandwidth. Virtualization allows fewer servers to

process more applications, thereby eliminating the need

to acquire more servers.

And a unied fabric means a server does not need sepa-

rate adapters and interfaces for LAN and storage trafc.

Combining both on the same network can reduce the num-

ber and cost of interface adapters by half, Layland notes.

And by eliminating the need for an aggregation layer of

switching, there are fewer switches to operate, support,

maintain and manage.

If you have switches with adequate capacity and

youve got the right ratio of input ports to trunks, you dont

need the aggregation layer, says Joe Skorupa, a Gartner

analyst. What youre doing is adding a lot of complexity

and a lot of cost, extra heat and harder troubleshooting

for marginal value at best.



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SEVEN RESOLUTIONS FOR NETWORK MANAGEMENTBy Jim Frey Network World

One analysts advice on how to keep your edge

Here are some suggestions for resolutions [as you look]

forward to the road ahead:

1Build an understanding of

IP videoconferencing.

Its big, its bad, and its going to change your

life, especially when desktop videoconferencing starts to

catch on. Videoconferencing is real-time, requires priority

QoS, low latency and many times more bandwidth than

VoIP. If you had to shake a few skeletons out of the wir-

ing closet when you rolled out VoIP, you better be ready

for a lot more skeletons. Start by nding out what type

of videoconferencing is being used or is planned for your

workforce, and gure out how much load this will create

on your network before it starts a viral ramp-up.

2

Become more application-aware.

How can you really be in tune with the business or

organization you are supporting if you dont know

where and how well the really important apps and services

are running? And in the converse, how can you understand

if the loads your network is carr ying are even relevant or just

so much streaming audio keeping remote ofce workers

entertained during the business day? Look to NetFlow (or

similar) data or packet-based monitoring tools to give you

this perspective.

3Start tracking user experience.

Even if you love the thrill of reghting and trou-

bleshooting gnarly performance issues across

distributed, n-tier architectures, the greatest satisfaction

(and kudos) can be gained by recognizing a problem

before calls start coming in to the help desk. And the

rst line of defense here is understanding what motivates

users to call the help desk their experience in using

(or trying to use) the applications and services which IT

provides. User quality-of-experience data can be gained

via on-client agents, synthetic trafc generators (whether

internally managed or externally subscribed), or by pas-

sively monitoring trafc and comparing request/response

patterns. Best practices employ a mix of these, but any

one is better than none.

4Think proactive/preventative.

Similar to #3, but more broadly speaking, an

ounce of problem prevention is worth at least a

pound of frantic troubleshooting cure. And there are lots

of options here. One of the most effective is to get better

change control in place, thus preventing the oops mo-



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ments when the upgrade you roll out breaks something

else (or a lot of other things). Others include using service

mapping and assessing health and risk on a sustained

basis, or using predictive analytics tools to help you sniff

out the important early warning signs of pending issues

hidden in all of that performance monitoring data youve

been collecting.

5Make friends with the system

admins and app support guys.

OK, maybe thats two resolutions, but its all

about getting along better. Unless you are in the minority,

your cross-organization working relationships usually look

more like a Big Fat Greek Wedding than one big happy

family. Take advantage of the fact that you can help tomeasure IT service delivery in a way that the other guys

cant in context with everything else that is going across

the wire and share that data openly and freely. Many

times, network-facing data can be the most effective

place to start the triage process when no one else is able

to get to the root of a problem.

6Embrace automation.

With the onslaught of virtualization (a.k.a. serv-

er hide and seek), mobility (a.k.a. client hide

and seek) and composite Web applications (a.k.a. you

guessed it application hide and seek) you wont be

able to keep up with all of the moving parts without auto-

mating discovery and upkeep of relationship recognition

and modeling. Automation is also available for respond-

ing to well-known event scenarios with pre-scripted ac-tions, change management for conguration roll-backs,

compliance auditing, and predictive analytics.

7

Figure out how to leverage

virtualization.

One of the more interesting evolutions of man-

agement technology is the growth in the number of hy-

pervisor platforms in place around your network. What

started purely as a computing system concept has rap-

idly spread to network equipment, so you can now deploy

management tools to new places as virtual images or vir-

tual appliances quickly and easily. Keep these in mind

when you are trying to work out how to achieve better

distribution of management tools and instrumentation.

Frey is a senior analyst with Enterprise Management

Associates.

Take advantage of the fact that you can help to measure IT service delivery in a way

that the other guys cant in context with everything else that is going across the

wire and share that data openly and freely.AN OPEN EXCHANGE

RETHINKING THE DATA CENTER NETWORK S d b
http://www.hp.com/http://www.networkworld.com/http://www.hp.com/http://www.hp.com/http://www.hp.com/


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White Paper

Redening the Economicsof Networking

See why Gartner and the network in-

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Freeing Your NetworkInfrastructure featuringGartner

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InnovationThroughEnd-to-End UnifiedNetworking SolutionsHP networkingfor midsize companiesSolutionbrief

Customer challengeBusinessesare strugglingto increase revenue andretaincustomer loyaltydue to constantcompetitivepressure to innovate quicklyanddeliver greater valueto their customers. Businesseslook to technologytohelpspur growth, cutcosts, andstayaheadofthecompetition.

Businessesare forcedto undergo digitaltransformationto remaincompetitive andenablenew serviceslike supplychainautomation, businessanalytics, manufacturingsystemsautomation, orderingsystems, andcustomer relationshipmanagement. Thesolutionto IT sprawl liesinaconvergedinfrastructurewhere IT silosare broughttogether into poolsofvirtualizedassets, sharedbymanyapplicationsandservices. The network isthe foundationofaconvergedinfrastructure. The systemsandapplicationsareall interconnectedover acritical IT infrastructurethe network.

Today, businessesseem shackledbyamix oflegacynetwork infrastructuresthatare difficultto expand,lack interoperability, andcosttoo much. Withtheboomingdemandfor mobile andfixedaccesstomultiple applicationsandservices, the rapidevolutionofwiredandwirelesstechnology, andthe proliferationofWLAN devicesandapplications, businessessimplylack the abilityto scale their networksefficiently, muchlessmanage andsecure them.

Due to these rapidchanges, businessesstruggle toremainagile andensure businesscontinuity. Networkexecutivesrelentlesslyseek aclear anddocumentedreturnoninvestmentfor every project. The networksmustbe simple to manage to supportsuchdiverseapplicationsandadaptto changingneeds, andtheymustbe cost-effective to supportbusinessobjectives.

Innovative HP solutionsInresponse to these challenges, HP networkingenablesbusinessesto do more withless. Throughabroadportfolio ofsecure unifiednetworkingproductsandsolutions, HP helpsbusinessestoreduce complexity, enhance businessagility, andmanage costs.

Reduced complexityThe network isthe foundationfor aconvergedinfrastructure andfor advancedapplicationslikeunifiedcommunicationsandcollaboration.

HP simplifiesthe network withaunifiedapproachwiredandwirelesshardware, software, management,andsecurity. HPsintegrated, easy-to-use managementfeaturesreduce the time andcomplexityofplanning,deploying, andoperatingwiredandwirelessLANsfrom asingle managementplatform. Thiseliminatesthe needto maintainmultiple managementstations,differentdevice andconfigurationpolicies, andaccessrights; italso eliminatesthe needto learndifferentsystems.

Securityisbuiltinto the network fabric asopposedto boltingiton. The HP ProActive Defense strategyenforcessecurityatthe network edge, where usersanddevicesconnect. Policiesare enforcedconsistentlyfor wiredandwirelessusersalike from the samemanagementsystem. Throughunifiedcore-to-edgeswitches, businessescanenable aconsistentcommandline interface, commonsoftware, andinterchangeablemodules. Inaddition, HPsoptimizedWLAN solutionsprovide simple andcost-effective migrationto IEEE802.11nenvironmentsthatscale to deliver high-speedWLAN capacityasbusinessesgrow.

1

Freeing your

network infrastructure

Featuringresearch from

Experience innovation with end-to-endunifiedsolutions

Freeingyour network infrastructure

The ConvergentPolicies of WiredandWireless LANs

AboutHP

Issue1

2

4

6

Executive summary ..............................................2Challenge amongchange.....................................2Proprietaryvs. openstandards...............................2

Value-drivensolutions...........................................2Breakingthe barriersofnetworking........................3Conclusion..........................................................4For more information............................................4

HP ProCurve businesswhite paper:Redefiningthe economicsofnetworking

Advancednetworkingthatbreak IT barriersandredefine the valueofnetworking

ProCurve Networkingby HP

InterconnectingtheIntelligentEDGE

Introduction .................................................. ...................................................... .......2

Networksin Transition ................................................................................................. 2

Performance................................................................................... .........................2

Scalability.................................................................... ........................................... 3

Security.............................................................. .................................................... 3

Quality ofService(QoS).......................................................... ..................................3

BusinessEfficiency........................................................ ........................................... 3

ProCurvesApproach toNetwork Design:Move Intelligence tothe EDGE .............. ...............4

ProCurvesIntelligentEDGE Solutions ............................................................................ 5

ProCurveIntelligentEDGE Switches.................................................... ........................5

ProCurveInterconnectFabric..................................................................................... 6

IntelligentEDGE NetworksversusTraditionalCoreNetworks ............................................. 6

TraditionalCoreNetworks .............................................. ........................................... 6

IntelligentEDGENetworks.................................................................................. .......7

TheValueof Deployingan IntelligentEDGE Network........................................................ 8

MinimizeInvestmentRisk................................................................. .........................8

ImproveNetworkPerformanceandAvailability............................................................. 8

Increase Network Security.............................................. ........................................... 8

Bolster ChoiceandFlexibility ..................................................................................... 8

Summary........................................................................ ........................................... 9

For More Information................................................................................................. 10

WH IT E PA PER

R OI o f Swit ch ed Et h ern et N et wo rkin g So lu t io n s f o r t h eMid m arket

Sponsored by: HP ProCurve

R a nd y P er r y A b ne r G e rm a no w

August2009

E x e c u t i v e S u m m a r y

Newgenerations of network equipment continueto be more reliable than previous

generations. Meanwhile, the applications running across the network have become

more ubiquitous and more demandin g. Underlying this cycle, the network has

become much more importantto businessesof all sizes inclu ding midmarket firms

and in all industries.

Driven bythe financial crisis, midmarket firms are takinga closelookat allbudgetl ine

items. Theydemandsolutionsthatprovid e morethan sufficient functionalityfortheir

current networking needs and also leave plentyof headroomto scale their network in

the years to come, in terms of both bandwidth and functionality. At the same time,

theywant these network systems to becost effective todeployand run.

One companystriving to address these n eeds is HP. HP ProCurve networking

productsinclude a broad line of LANcoreswitches,LANedge switches,and wireless

LANand network securitysolutions that are all brou ght together under a unifiedmanagement suite. To determine the return on investment (ROI) associated with

implementation of an HP ProCurve network solution, IDCconducted a study of

medium-sized to large organizations with an HP ProCurve implementation up andrunning in theirproduction environment. IDCestimates thatthese businesses were

ableto achieve a 473%ROI; a three-year(discounted) benefitof $38,466per100

users; and payback on their initial investment within 5.7 months.

N e t w o r k Infr a st r uct u r e G r o w t h D r i v e r s i nT o d a y ' s M i d ma r k e t E nv i r o nme nt s

The ITindustryingeneral andthenetworking market inparticularare finallyshowing

signs of stabilizing after the financial crisis of late 2008/early200 9. Looking forward,

IDCanticipates that networking will rebound morestronglythan other areas of IT

spending, driven bythe fact that the recession has not changed the fundamental

reasons for businesses to continue investing in their networks. Major drivers for

midmarket firms to continue investingin networking equipment include:

MigrationofvoiceandvideotoIP. Asbusinesseslook toreduceexpenses by

adoptingtechnologiessuch asvideoconferencingandvoice overIP,theincreasing

amount of v oiceandv ideot r af f ic is c r eat ingnew c hallenges f or t henetw or k .

R es pons et imes f or W ebs ites or appl ic ations of upt oa s ec ondus edt obe

acceptable,butthehumaneye andearcandetectdel aysmeasuredinmilliseconds.

Simplythrowingbandwidthat theproblemis insufficientasthemix ofapplication

demandson thenetworkrises.Midmarket firmsmustincorporate newlevelsof

bandwidthandintelligenceinto theirnetworktohandlethese morecomplexquality-

of-servicerequirements.

GlobalHeadquarters:5SpeenStreetFramingham,MA01701USA

P.508.872.8200

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Rethinking the Data Center Network

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