10gbase-t: to shield or not to shield, thatto shield, that ... · 10gbase-t: to shield or not to...
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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
1.5
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Stre
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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