10GBASE-T: To Shield or Not To Shield, That’s A DilemmaTo Shield, That s A Dilemma

Dr. T. C. TanDistinguished Member, CommScope LabsDistinguished Member, CommScope Labs

TopicsTopics

• EMC Standards• EMC Standards • 10GBASE-T Cabling Specifications• Claims and Facts• Grounding/Earthing & Bondingg g g• Summary/Conclusion

EMC St d dEMC Standards

EMC StandardsC SUS: FCC Part 15

IECCISPR 22

Class A(Commercial)

ProductEmissionStandard

Cl BEN 55022

CENELEC

Class B(Domestic/Residential)

Class B limit is intended primarily for the domestic environment. The domestic environment is an environment where the use of broadcast radio and TV receivers may be expected within a distance of 10 m of the apparatus concerned.

EMC StandardsUS: No immunity

requirements

C S

CISPR 24 IEC

ProductImmunity

Performance Criteria A(No Errors)Performance Criteria BImmunity

StandardPerformance Criteria B(Errors Permitted)

Performance Criteria C(Errors and Manual

EN 55024CENELEC

(Errors and ManualReboot)

EMC Standards

IEC

C S

IEC61000-6-361000-6-4 Class 1

(Residential, Commercial,Light Industry)

GenericEmissionStandard

Light Industry)Class B Limit

Class 2(Heavy Industry)

Class A LimitEN

61000-6-3CENELEC

Class A Limit61000-6-361000-6-4

However, Product standards take precedence over Generic standards.

EMC Standards

IEC

C S

Class 1

IEC61000-6-161000-6-2

GenericImmunity

(Residential, Commercial,Light Industry) Performance Criteria A

(No Errors)Performance Criteria BStandard

EN

Class 2(Heavy Industry)

Performance Criteria B(Errors Permitted)

Performance Criteria C(Errors and ManualEN

61000-6-161000-6-2

(Errors and ManualReboot)

CENELEC

However, Product standards take precedence over Generic standards.

EMC StandardsIEC/EN 61000-6-1 vs 61000-6-2

IEC/EN 61000 6 1 IEC/EN 61000 6 2

C S

Immunity TestsIEC/EN 61000-6-1

(MICE E2)Offices, Light Industrial

IEC/EN 61000-6-2(MICE E3)

Heavy Industrial

ElectroStatic Discharge (ESD) IEC 61000-4-2

Radiated Immunity IEC 3 V/m 10 V/m

Contact Discharge: 4 kV Air Discharge: 8 kV

Contact Discharge: 4 kV Air Discharge: 8 kV

Radiated Immunity IEC 61000-4-3

Electrical Fast Transients (EFT) IEC 61000-4-4

3 V/m80 MHz to 1 GHz

10 V/m80 MHz to 1 GHz

500 V 1000 V(EFT) IEC 61000 4 4

Conducted Immunity IEC 61000-4-6

3 V/m0.15 MHz to 80 MHz

10 V/m0.15 MHz to 80 MHz

Power Frequency Magnetic Field Immunity IEC 61000-4-8 3 A/m 30 A/m

EMC StandardsField Strength Surveys (up to 1 GHz)

3

EN 55024 Limit

C S

2

2.5

EN 55024 Limit

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EMC Standards

Applicable EMC Standards for ITE

C S

ppin Commercial Environment

IEC CISPR 22EN 55022

IEC CISPR 24EN 55024

ProductImmunityStandard

ProductEmissionStandard

Shielding Affects Internal Parameters

• When a shield is added to a UTP cable, the

g

,following happens:– Shield changes the capacitive and inductive

coupling of the overall cable. C increases and L decreasesAtt ti [ b ll i t d t b– Attenuation [can be well approximated to be proportional to √(C/L)] increases

– Balance (TCL/LCL) degrades– Balance (TCL/LCL) degrades

Cl i d F tClaims and Facts

Claims and FactsClaim: • Data Centres are a “harsh environment” due to the• Data Centres are a harsh environment due to the

presence of large quantity of powered equipment

F tFact: • Data Centres are no harsher than a large

Communications RoomDi t b f id ti l ITE (IT i t) ll– Disturbances from identical ITE (IT equipment) are generally not additive in practice (IEC CISPR 22 Clause 8.1)

– FCC and/or IEC/EN emission limits must be met irrespective of whether there is one switch or one hundred switches

• ANSI/TIA-942 and EN 50174-2:2008 have power separation guidelines. Some vendors do provide p g pguidelines

Claims and Facts

IEC CISPR 22:1997 – Clause 8.1

Claims and FactsClaim• The received 10GBASE-T signal has low tolerance to

noise, and requires shielded cabling

Fact• All ITE must be designed to meet immunity limits per

IEC CISPR 24/ EN 55024This is a requirement under EU regulation– This is a requirement under EU regulation

• Vendors must provide documented design, installation, field testing and grounding/earthing guidelines. These are very important for proper EMC and functionalare very important for proper EMC and functional performance. It is also a requirement under the new EMC Directive 2004/108/EC

• Some vendors offer EMC Compliance as part of their application support

Claims and Facts

Claims and Facts

Claims and Facts

ClaimC t 6A FTP d STP t h• Cat 6A FTP and STP systems have more alien crosstalk margin than UTP and therefore are less riskytherefore are less risky

Fact• See next slide

Facts (Alien Crosstalk)• IEEE 802.3an includes Class EA specifications to enable

UTP to 100 m including alien crosstalk requirements

Facts (Alien Crosstalk)

UTP to 100 m, including alien crosstalk requirements• Alien crosstalk channel requirement does exist for

1000BASE-T and yet there is no problem• Alien crosstalk, like other critical parameters such as

balance and coupling attenuation, will be met by design• All vendors must guarantee that their solutions meet g

the IEEE alien crosstalk limits for both near-end and far-end– Must include both worst pair and average limitsMust include both worst pair and average limits– Live 10GBASE-T network over UTP has been demonstrated at

many public events

Key 10GBASE-T DemosyCTV Analyst Mtg, RichardsonSolarFlare Evaluation BoardsDec ’06

Cisco Networkers, Los AngelesDell/SolarFlare NICs

SuperComputing ‘07, Reno

Feb ’07

Nov ’07 Cisco 6500 & Intel NICsCisco Networkers, Barcelona

Cisco 6500 & Intel NICs

Nov 07

Jan ’08

Interop, Las VegasSolarflare NIC SNR on various cabling

HP Tech Forum Las Vegas

Apr ’08

J ’08 HP Tech Forum, Las VegasSMC Switch & Solarflare NICs

Cisco Networkers, OrlandoCisco 4900 & Intel NICs

Jun ’08

Jun ’08 Cisco 4900 & Intel NICsCisco Networkers, Barcelona

Cisco 4900 & Dell/Solarflare NICsJan ’09

Claims and Facts

ClaimClaim• Cat 6A FTP and STP systems have higher

Shannon Capacity than Cat 6A UTP – ideal for f t li tifuture applications

FactsFacts• See next slides

Shannon Capacity

Facts (Shannon Capacity)Facts (Shannon Capacity)

• Shannon capacity calculations provide an early p y p ytool to estimate DSP needs and select media

– Calculations subject to a number of variables/ ( f fassumptions, (max. frequency, length, number of

adjacent channels, background noise, etc.)• All applications specify cabling channel• All applications specify cabling channel

performance requirements, not Shannon Capacityp y

• Let’s take a look at the latest development in IEEE, i.e. 40/100 GbE

Copper: 100G on Class F /Cat 7 ?Copper: 100G on Class FA/Cat 7A?• Nov 2007: Presentation from the Pennsylvannia

State University

Copper: 100G on Class F /Cat 7 ?

• Measured 2 connection Class F /Cat 7 channels to 3 GHz

Copper: 100G on Class FA/Cat 7A?

• Measured 2-connection Class FA/Cat 7A channels to 3 GHz– Not a 4-connection channel and 2 GHz beyond Class FA

specification!• Based on Shannon capacity calculations

– 100 metre support not possible• Complexity and practical implementation issues not taken• Complexity and practical implementation issues not taken

into consideration– Very complex transceiver– No ADC (analog-to-digital converter) available for sometime– A nice, educational R&D exercise

Copper: 40/100G ProposalCopper: 40/100G Proposal

From IEEE HSSG Interim Meeting Sept ’07 presentation: diminico 09_01_07.pdf

Claims and Facts

ClaimClaim• Cat 6A FTP and STP cables are smaller than Cat 6A

UTP cables

Facts• See next slides

Cable Size and Tray FillyVendor P

10GCat 6A STP

Vendor S10G

C t 6A FTP

Vendor C10G UTP

Cat 6A FTP

7.9 mm

86 82 80

7.7 mm 3091A: 8.00 mm 3091B: 7.24 mm

9786 82 80

(100: for 50%)100 x 100 mm tray/basket, 40% fill factor

97

(121: for 50%)

Cables and Cords: bending and flexibility

Angled entry for Vendor C 10G UTP cable at outletNot possible with FTP/STP cables.p

B d di d lBend radius and plug length for FTP/STP CablesRequires more clearance than UTP i bi t k tUTP in cabinets, racks, etc.

Claims and Facts

ClaimClaim• FTP/STP cabling must be used in the

presence of noise (irrespective of the noisepresence of noise (irrespective of the noise frequency)

Facts• See next slidesSee next slides

Facts

• At low frequencies, the noise pickup in a shielded cable is the same as for an unshielded cable. For example, an aluminium or copper shield of about 1 mm thickness will only provide approximately 1 dB loss at y p pp y50 Hz (power cable) frequency

SE R + A + MR dBSE = RL + AL + MRL dBwhere,

SE is Shielding EffectivenessgRL is the Reflection LossAL is the Absorption LossMRL is the Multiple Reflection Loss

Facts

A = 0 1314 * d * f m s dB

Facts

A = 0.1314 * d * f mr sr dB

wherewhere,

mr is the relative permeability (to free space)

i th l ti d ti it (t )sr is the relative conductivity (to copper)

f is the frequency of wave, Hz

d is the thickness of the shield, mm

Claims and Facts

Claim• Shielded cabling can have much lower power

consumption ...... Reason is No Echo Cancellation !!

Facts• Need to differentiate between the types of shielded yp

cabling – FTP or STP• NEXT, FEXT and Echo cancellations are required for

UTP d FTP tUTP and FTP systems• Echo cancellation is required for STP systems• See next slides• See next slides

FactsFacts

Applies to both UTP, FTP and STP

E thi G di & B diEarthing, Grounding & Bonding

Electrical Mains Systemsy

TN-S system:TN-S system:Recommended for FTP/STP cabling systemssystems

TN-C system:C systeNot recommended for FTP/STP cabling systemssystems

Die Normengerechte Installation geschirmter Systeme „Praxisbeispiele“ A requirement in Austria and

some parts of Germany

Grounded Outlets

S /C l iSummary/Conclusion

Key Reasons Why Some VendorsKey Reasons Why Some Vendors Recommends UTP for 10G

• Class EA compliance for 10GBASE-T support to 100 m• Avoids issues with earthing/grounding and bonding

A id i ith l t i t• Avoids issues with power supply system requirements (TN-S system recommended for all shielded systems)

• Avoids extra termination steps related to screen, drainAvoids extra termination steps related to screen, drain wire (i.e. shorter termination time)

• Avoids maintenance of screen/shield integrity over time• Less space required for work area connector housing

and cable/cord bend radius• Preferred twisted pair cabling media worldwide• Preferred twisted pair cabling media worldwide

Conclusion• Alien crosstalk compliance for 10GBASE-T can be

achieved either by– Using the traditional shielding approach, or

– Using innovative UTP design and advanced system level tuning of cable, cords, and connectors, orof cable, cords, and connectors, or

– Physical separation• EMC compliance for 10GBASE-T can be achieved in the

f ll ifollowing ways:– Proper balance of cabling and equipment interfaces– Filtering through the use of common mode chokes. These are g g

located at the NICs and switches– Use of bandwidth efficient coding techniques– Shielding with proper grounding & bonding practices, correctShielding with proper grounding & bonding practices, correct

cabling shield termination procedures and maintaining shield integrity

Conclusion

• EMC compliance for 10GBASE-T (cont)– LAN equipment should be well designed with EMC in

mind. This is within the designer’s controlCabling installations have too many variables and– Cabling installations have too many variables and very difficult to control Difficult to achieve good and clean ground. For ScTP/FTP

and STP cabling system, this is an essential requirement. Good and clean ground maintenance is expensive

So cabling should be simple, easy to install and easy to maintain. Let the equipment perform the EMC management

Th k YThank You