Cisco Online Study test versus reality

I just took the study Exam 1 test available on Cisco website.

According to the results of my test Cat5 cable cannot run at the speed of 1GB.

The Odom book says it can run at 1GB. I belive to book to be right and the test to be wrong but I wanted to hear what other thought.

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networker050184

Cat5 up to 100mb

Cat5e up to 1gb

scheistermeister

T88 wrote:

I just took the study Exam 1 test available on Cisco website.

According to the results of my test Cat5 cable cannot run at the speed of 1GB.

The Odom book says it can run at 1GB. I belive to book to be right and the test to be wrong but I wanted to hear what other thought.

If you are talking about the tests from the prep centers there are a few questions in those that are wrong. Especially with the BCMSN test. But you also have to realize the difference between Cat5 and Cat5e...

T88

It is most commonly used for 100 Mbit/s networks, such as 100BASE-TX Ethernet, although IEEE 802.3ab defines standards for 1000BASE-T - Gigabit Ethernet over category 5 cable.

From: http://en.wikipedia.org/wiki/Category_5_cable

tech-airman

T88 wrote:

I just took the study Exam 1 test available on Cisco website.

According to the results of my test Cat5 cable cannot run at the speed of 1GB.

The Odom book says it can run at 1GB. I belive to book to be right and the test to be wrong but I wanted to hear what other thought.

T88,

Category 3 cabling is designed and certified for 10 Mbps performance. Category 5 cabling is designed and certified for 100 Mbps performance. By design, you should be using Category 6 cabling for 1 Gbps performance. In other words, for each Category level, there's a corresponding intended speed for it.

For a cable or channel to be certified for a certain category level, there are required tests to be passed. Only if all tests pass can the cable or channel be certified as Cat # rating. Generally speaking, Cat 3 has less tests to pass than Cat 5, Cat 5 has less tests to pass than Cat5e, and Cat5e has less tests to pass than Cat 6. It is because of these tests that must be passed to be certified which is what makes certified Cat 6 cabling more expensive than Cat 5e, Cat 5, and Cat 3. It is because of that expense that some people are deciding to use the cheaper Cat 5 cabling and take their chances that it supports 1 Gbps speeds than to do the correct thing and use Cat 6 cabling for ther Gigabit links.

So yes, from a standard, design, and engineering perspective, Cat 5 cabling is designed for 100 Mbps performance but NOT 1 Gbps performance. So I say that the book is wrong to be teaching you something that is in violation of the standard that the Category system is based on and the test is right from the point of view of the actual Category 5 standard which is intended for 100 Mbps performance.

astorrs

Sorry guys, but when 1000Base-T was defined as 802.3ab by IEEE and the GEA it was done so against Cat-5.

The 1000BASE-T standard outlines operation, testing, and usage requirements of Gigabit Ethernet for the installed base of CAT-5 copper wiring, which includes most of the cabling within buildings.

http://standards.ieee.org/announcements/802.3ab.html

So the answer to the book question is "Yes, 1000Base-T is supported over Cat-5 wiring."

Would I ever do it in real life? Probably not. Cat-5e is my minimum usually (Cat-6 for new data centers).

tech-airman

astorrs wrote:

Sorry guys, but when 1000Base-T was defined as 802.3ab by IEEE and the GEA it was done so against Cat-5.

The 1000BASE-T standard outlines operation, testing, and usage requirements of Gigabit Ethernet for the installed base of CAT-5 copper wiring, which includes most of the cabling within buildings.

http://standards.ieee.org/announcements/802.3ab.html

So the answer to the book question is "Yes, 1000Base-T is supported over Cat-5 wiring."

Would I ever do it in real life? Probably not. Cat-5e is my minimum usually (Cat-6 for new data centers).

astorrs,

The term "Category 5" is defined by the standards of the following organizations:

American National Standards Instutute (ANSI)
International Cable Engineers Association (ICEA)
Electronic Industry Alliance (EIA)
Telecommunications Industry Association (TIA)
International Organzation for Standardization (ISO)
International Engineering Consortium (IEC)

The relevant standards are:

ANSI/EIA/TIA-568A - Obsoleted by ANSI/EIA/TIA-568B
ANSI/ICEA S-90-661-2002 - http://www.icea.net/Public_Pages/Documents/Document_Scopes/S-90-661-2002_WebSum.pdf
ISO/IEC 11801

ANSI is the United States governmental standards organization. ANSI is the United State's member organization within the ISO organization. The ISO is like the United Nations for Standards. IEEE on the other hand is a non-governmental professional industry organization. Since the IEEE 802.3ab standard references "CAT-5 copper wiring" then the definition of the term "Category 5" within the ANSI/EIA/TIA-568A standard applies. Since ANSI/EIA/TIA-568A specifies that "Category 5" cabling standard supports throughputs of up to 100 Mbps, using a "Category 5" cable for the intent of using it in 1 Gbps links is exceeding it's intended throughput and thus a violation of the ANSI/EIA/TIA-568A standard. So this is a case of should use Category 5 for 100 Mbps vs. shouldn't use Category 5 for 1 Gbps. It's also a case of Category 5 cabling can operate at 1 Gbps vs. it's not certified to continously operate at that throughput due to the ANSI/EIA/TIA-568A standard definition for "Category 5."

Source:

American National Standards Institute (ANSI) - http://www.ansi.org/
Insulated Cable Engineers Association (ICEA) - http://www.icea.net
Electronic Industry Alliance (EIA) - http://www.eia.org
Telecommunications Industry Association (TIA) - http://www.tiaonline.org
International Organization for Standardization (ISO) - http://www.iso.org
International Engineering Consortium (IEC) - http://www.iec.org
Cat 5 - definition of Cat 5 from YourDictionary.com - http://www.yourdictionary.com/cat-5

astorrs

Thanks for the good links, I'm sure others will find them helpful in understanding how many parties are involved in setting global standards.

I think your confusion is coming from the fact that you are mixing up Mhz and Mbps. The original ANSI/TIA/EIA-568-A document defined the test parameters and expected performance of the cable up to 100Mhz. Prior to the finalization of 802.3ab, 155Mbps ATM was already supported over Cat-5 for short distances up to 300ft.

When 802.3ab was finalized they had to define new performance tests to ensure it would work over 4-pair Cat-5 UTP which TIA/EIA did with TSB95. This bulletin was integrated into ANSI/TIA/EIA-568-B.1-2001 as Annex D and replaced ANSI/TIA/EIA-568-A as the standard for testing Cat-5 cabling installations.

As such not all Cat-5 cables and connectors that were installed prior to 1999 (when TSB95 was released) would meet the revised tests (i.e., how could the contractors have tested it against a set of tests that didn't yet exist). I know because we had to replace some in 2000 when we upgraded some backbone links

, and we replaced it with new UTP cable and then tested it to the ANSI/TIA/EIA-568-A Cat-5 standard with the additional tests for channel return loss and ELFEXT transmissions from TSB95.

Later on to simplify things for both contractors and customers (and for prototyping of 10Gb Ethernet) Cat-5e was defined as a separate standard and Cat-5 was deprecated. It also is tested to only 100Mhz.

Cat-6 is tested to 250Mhz (supports 1000Base-T) while Cat-6a is tested up to 500Mhz (supports 10GBase-T).

I hope that clears things up for everyone.

tech-airman

astorrs,

astorrs wrote:

Thanks for the good links, I'm sure others will find them helpful in understanding how many parties are involved in setting global standards.

I think your confusion is coming from the fact that you are mixing up Mhz and Mbps. The original ANSI/TIA/EIA-568-A document defined the test parameters and expected performance of the cable up to 100Mhz. Prior to the finalization of 802.3ab, 155Mbps ATM was already supported over Cat-5 for short distances up to 300ft.

From what I recall from my physics courses, the unit hertz or Hz for short is associated with waves. The unit hertz refers to "cycles per second." So one cycle or wave per second is a hertz. With computer networking, there's analog and digital signals. The technology using analog signals is called Broadband. The technology using digital signals is called Baseband. Examples of Baseband technologies include 10BASE-T, 100BASE-TX, and 1000BASE-T. An analog signal looks like a sine wave like below:

A digital signal looks more like a square wave like below:

The main difference between a Broadband signal and a Baseband signal is that the first is like the curved sine waves and the second is like the square waves. Here's a diagram comparing the two types of waves.

A single square wave can hold the information of 1 bit. 1 bit per second would equal 1 bps which is the same as 1 cycle per second or 1 Hz. That means, there is a 1 to 1 ratio between bits and cycles. That also means 1 bit per second is the same as 1 cycle per second. Therefore:

Analog = Digital
Broadband = Baseband
10 MHz = 10 Mbps
100 MHz = 100 Mbps

Therefore, Category 5 cabling that was tested and certified to 100 MHz was also tested and certified to 100 Mbps throughput standard.

Source:

"Periodic Waveforms" webpage at ByteNoise
[list=1:3e5845ce3f]
- http://music.bytenoise.co.uk/sine_wave.jpg
- http://music.bytenoise.co.uk/square_wave.jpg

[*]"Atmel Ultrasonic Ranger" webpage at Craig's Area - http://www.craigsarea.com/images/ultra_comparator.jpg
[/list:o:3e5845ce3f]

astorrs wrote:

When 802.3ab was finalized they had to define new performance tests to ensure it would work over 4-pair Cat-5 UTP which TIA/EIA did with TSB95. This bulletin was integrated into ANSI/TIA/EIA-568-B.1-2001 as Annex D and replaced ANSI/TIA/EIA-568-A as the standard for testing Cat-5 cabling installations.

Are you sure it was ANSI/TIA/EIA-568B.1? I thought ANSI/TIA/EIA-568B.1 was called "General Requirements." Doesn't ANSI/TIA/EIA-568B.2 cover copper cabling?

astorrs wrote:

As such not all Cat-5 cables and connectors that were installed prior to 1999 (when TSB95 was released) would meet the revised tests (i.e., how could the contractors have tested it against a set of tests that didn't yet exist). I know because we had to replace some in 2000 when we upgraded some backbone links , and we replaced it with new UTP cable and then tested it to the ANSI/TIA/EIA-568-A Cat-5 standard with the additional tests for channel return loss and ELFEXT transmissions from TSB95.

Later on to simplify things for both contractors and customers (and for prototyping of 10Gb Ethernet) Cat-5e was defined as a separate standard and Cat-5 was deprecated. It also is tested to only 100Mhz.

Category 5 was defined in ANSI/TIA/EIA-568A. Category 5e was defined in ANSI/TIA/EIA-568B.2. Since ANSI/TIA/EIA-568A was made obsolete by ANSI/TIA/EIA-568B, that's why "...Cat-5 was deprecated..." to use your term.

astorrs wrote:

Cat-6 is tested to 250Mhz (supports 1000Base-T) while Cat-6a is tested up to 500Mhz (supports 10GBase-T).

I hope that clears things up for everyone.

IEEE 802.3ab achieves it's 1000 Mbps throughput by using all four pairs of cables in the UTP cable. So since there are four pairs being used, each pair only needs to achieve 250 MHz performance. Therefore 4 x 250 MHz = 1000 MHz. Since 1 Hz = 1 bps, 1000 MHz = 1000 Mbps = 1 Gbps.

astorrs

tech-airman wrote:

Are you sure it was ANSI/TIA/EIA-568B.1? I thought ANSI/TIA/EIA-568B.1 was called "General Requirements." Doesn't ANSI/TIA/EIA-568B.2 cover copper cabling?

Yes I'm sure the additional tests were incorporated into Annex D entitled "CATEGORY 5 CABLING TRANSMISSION" of ANSI/TIA/EIA-568-B.1-2001. I'm looking at a copy of it.

tech-airman wrote:

IEEE 802.3ab achieves it's 1000 Mbps throughput by using all four pairs of cables in the UTP cable. So since there are four pairs being used, each pair only needs to achieve 250 MHz performance. Therefore 4 x 250 MHz = 1000 MHz. Since 1 Hz = 1 bps, 1000 MHz = 1000 Mbps = 1 Gbps.

Okay Mr. Smarty Pants

Explain how 1000Base-T works off Cat-5e (4-pair UTP tested from 1-100Mhz) using your clock/frequency range formula. Your calculations don't account for encoding, this isn't the old hz = bps days of 300 "baud" modems.

tech-airman

astorrs,

astorrs wrote:

tech-airman wrote:

Are you sure it was ANSI/TIA/EIA-568B.1? I thought ANSI/TIA/EIA-568B.1 was called "General Requirements." Doesn't ANSI/TIA/EIA-568B.2 cover copper cabling?

Yes I'm sure the additional tests were incorporated into Annex D entitled "CATEGORY 5 CABLING TRANSMISSION" of ANSI/TIA/EIA-568-B.1-2001. I'm looking at a copy of it.

Ok, I only have notes from my cabling class so I guess your copy of ANSI/TIA/EIA-568-B.1-2001 Annex D trumps my notes.

astorrs wrote:

tech-airman wrote:

IEEE 802.3ab achieves it's 1000 Mbps throughput by using all four pairs of cables in the UTP cable. So since there are four pairs being used, each pair only needs to achieve 250 MHz performance. Therefore 4 x 250 MHz = 1000 MHz. Since 1 Hz = 1 bps, 1000 MHz = 1000 Mbps = 1 Gbps.

Okay Mr. Smarty Pants

Explain how 1000Base-T works off Cat-5e (4-pair UTP tested from 1-100Mhz) using your clock/frequency range formula. Your calculations don't account for encoding, this isn't the old hz = bps days of 300 "baud" modems.

According to ANSI/ICEA S-90-661-2002 dated June 27, 2002 by ANSI, Category 5e is certified up to 125 MHz and not 100 MHz. My "clock/frequency range formula" was relevant for my point that Category 5 was rated for 100 Mbps. I just extrapolated from Category 5 to Category 6 in order to explain how you get 1 Gbps performance out of Category 6 cabling that is only rated to 250 MHz.

To address your rebuttal and question, there's at least two factors that I'm aware of which are:

Manufacturing
Technology and networking devices

I remember once upon a time when there was the wonderful world of floppy disks. There were 5 1/4" floppy disks as well as 3 1/2" floppy diskettes. Back in those days, just like today, we were inundated with acronyms. For example, SSSD, SSDD, DSDD, DSHD. SSSD stood for "Single Sided Single Density." SSDD stood for "Single Sided Double Density." DSDD stood for "Double Sided Double Density." DSHD stood for "Double Sided High Density." Who here remembers buying SSDD 5 1/4" floppy disks, then using a single hole punch clipped out a second notch in the 5 1/4" floppy disk so you can use the second side of a Single Sided floppy disk so you can get more storage space for the same cost? Even though due to non-certification by the manufacturer that the second side is actually usable, even if you got 1 bit more storage space on side 2, you were still getting more for the same amount of money. Then the diskette manufacturing industry put a stop to that by making the 3 1/2 " floppy disks. That's because, 3 1/2" flopppy disks were only intended to be inserted into the floppy disk drive one way and simultaneously used both sides of the floppy disk material. However, in the 3 1/2" floppy disk world, there was a difference: 1) DSDD and 2) DSHD. The physical difference was that the DSHD floppy diskettes had an extra open window in the opposite corner from the write enable/write protect tab and DSDD floppy disketts didn't. However, imagine you're the manufacturer of the floppy diskettes. Let's say that testing is done to the floppy disks before their encased in their final plastic cover. Let's say you're manufacturing DSHD floppy diskettes. But what if that DSHD intended floppy disk failed the quality control tests for DSHD standards, but was good enough for DSDD standards? Well, that floppy disk was probably NOT thrown away because it's a "DSHD floppy disk failure." Instead, it was probably encased into a DSDD 3 1/2" case then sold as a DSDD 3 1/2" floppy diskette. At least this way, maybe the manufacturer might be able to recoup their costs of manufacturing the floppy disks by making the DSDD floppy diskette instead of throwing it away as a DSHD reject.

Another example that I could imagine was Intel and back in the days of the 80386 processor. As you may or may not recall, the 80386 came in two flavors: 1) 80386 DX and 2) 80386 SX. The difference between the DX and the SX is that the DX had a math coprocessor and the SX didn't. Well, imagine you're Intel and you're trying to manufacture 80386 DX CPUs. But, during Quallity Control testing, you find that the "math coprocessor" circuitry of the CPU was defective or malfunctioning. Soo, instead of throwing out those "80386 DX" rejects, just repackage it as a "80386 SX." Since most of the 80386 CPU worked, why not? Now, here's another irony. What if the "80386 DX" CPU had a functioning coprocessor circuit but the non-functioning main CPU circuit? Just repackage it as a "80386 Coprocessor" and sell it for the computer systems with a "80386 SX" on board, with a "coprocessor slot" for future expansion.

Now, we're currently under the ANSI/TIA/EIA-586B cabling standard that defines Category 5e that obsoleted the ANSI/TIA/EIA-586A standard that defined Category 5. Once again, manufacturers are out there making the products such as UTP cabling. There's at least two scenarios: 1) the UTP cable manufacturer has both equipment and machinery to make Category 5e UTP cables and Category 6 UTP cables or 2) the UTP cable manufacturer has got rid of their Category 5e UTP cable manufacturing equipment and upgraded to Category 6 UTP cable manufacturing equipment. In the first scenario, the UTP cable manufacturer may simply be trying to recapture a return on investment of purchasing the Category 5e UTP cable manufacturing equipment so that's why they're still retaining the equipment and making Category 5e UTP cabling. In the second scenario though, what if the Category 6 UTP cable manufacturing equipment is "backwards compatible" and is able to make both Category 5e UTP cabling or Category 6 UTP cabling. Interpolating from Category 1 to Category 5, the main difference is from low to high pair twisting. Also, the overall quality standards of both the copper materials and the manufacturing processing involved to achieve Category 6 or higher quality. This is simply the consequences of improved manufacturing processes over time. So let's say the UTP cabling manufacturer is intending to make Category 6 cabling. However, during the Quality Control phase, that cabling does NOT meet Category 6's stricter tolerances for meeting the standard BUT that cabling meets the standards for Category 5e. So just like floppy disk manufacturers and Intel, instead of throwing out the "Category 6 reject" cabling, just repackage it as a "Category 5e" cabling. If you can't use it for data networking, might as well use it for something like internal telephone wiring for new buildings and homes. Also with DSL service, it's better to have Category 5e cabling than POTS cabling. The point is, that "Category 6 reject repackaged as Category 5e" may have failed Category 6 standards due to failing at 250 MHz but may be good enough for 240 MHz. So in this case, this "reject" far exceeds the 125 MHz requirement for Category 5e to _almost_ the point where it can achieve the 250 MHz requirement for Category 6. So, kinda like the "use a hole punch on a SSDD 5 1/4" floppy disk" trick, the buyer of the "Category 5e" cabling may be getting quasi-Category 6 quality. Also remember that it is the test segment for the cabling that failed the quality control test, not the whole box/roll/spool. Also, due to quality control reasons, it is unlikely that the UTP cable manufacturer will intentionally make "crappy cable to only meet Category 5e standards."

Then there's the whole issue of encoding and also compression of the data, segment, packet, and frame by the networking device before the bits hit the wire. So yes, that's when my "clock/frequency range formula" breaks down. So to answer your question, the frequency band between the 125 MHz that Category 5e standards requires and the 250 MHz requirement for Category 6 may be bridged by the encoding and compression techniques to effectively create a 1000 Mbps or 1 Gbps link performance.

Source:

ANSI/ICEA S-90-661-2002 dated June 27, 2002 - http://www.icea.net/Public_Pages/Documents/Document_Scopes/S-90-661-2002_WebSum.pdf

astorrs

OMG, it continues.

I have to admit, I hadn't thought about either floppy disks or x386 chips in a long (long) time, and it was kind of funny to think about how those practices still remain today (Ghz ratings for CPU's, etc).

I'm gonna have to go have a few drinks before I can reply to that - it's Friday night here after all. Can we pick-up tomorrow?

astorrs

First a few definitions so we’re all on the same page:

Hz = measured in cycles /sec (bandwidth)

baud = symbols or pulses/sec (signal rate)

bps = bits transferred /sec (bit rate)

Back around the dawn of time, okay the early 1960’s (close enough for me :P), the 300 bps modem was developed. It operated on a form of frequency modulation in which one binary bit mapped to one symbol (and each symbol mapped to a specific frequency). As such 300 baud = 300 bps, then following Shannon we get 300 Hz. That was the last time they were all equal. For 1200 bps modems they switched to digital modulation with a baud rate of 600 and 2 bits per symbol, still at 300 Hz. It got "worse" from there.

Moving back to Ethernet, 10Base-T runs over 2 pairs of UTP Cat-3 cabling (one transmit, one receive) at up to 20 MHz (due to the inclusion of the clock data this will vary) and uses Manchester encoding to achieve 10 Mbps speeds.

For 100Base-TX they opted to use a 4B/5B conversion which makes sure that all symbols include at least 2 changes of state and never more than 3 identical bits are sent in sequence. The problem was by converting 4 bits to 5, so they increased the signal frequency by 25% to 125 MHz. Since Cat-5 cable was only rated to 100 MHz they applied a side-stream scrambler to spread the signal energy across the entire spectrum (“spread-spectrum”) and then applied an encoding scheme called Multi-level Threshold 3 (MLT-3).

This had two benefits: First by scrambling the data no single frequency gets sent for any substantial amount of time (essentially “whitening” the frequency) and the radiated power looks like noise, thus satisfying the strict FCC requirements on transmissions above 30 Hz. Secondly, MLT uses 3 physical levels to reduce the signal to one forth its original frequency (or 31.25 MHz). Also 100Base-TX is never idle, it maintains a constant “chatter” to keep the two sides synced (since the clock is not being sent along with the data as it was in 10Base-T, this holds true for 1000Base-T as well).

They had to redo things again for 1000Base-TX. Because of the IEEE’s work with 100Base-T2 (which was never marketed due to the prevalence of 100Base-TX when the T2 standard was finally completed) they opted to use the same 5-level Pulse Amplitude Modulation (PAM-5) encoding scheme they had used for 100Base-T2, along with its capability for full-duplex transmission while dealing with crosstalk from adjacent pairs. They also borrowed the 125 MHz rate from 100Base-TX to allow for simpler 100/1000 implementations.

To achieve 1000 Mbps using 4 pairs, each pair had to be able to handle a 250 Mbps data rate. The use of hybrids (a technique for coupling the transmitted data and received data – very complex devices, like advanced solid state transformers, without the transformer) allowed for full duplex operation (transmit and receive at the same time over the same wire pair). In PAM-5 each transmitted symbol represents one of 5 voltage levels (-1V, -0.5V, 0, +0.5V, +1V – usually labeled as -2, -1, 0, +1, +2). Only 4 levels are really required for 2 bits/symbol encoding since there are only 4 possible combinations (00, 01, 10,11), I explain why there is 5 later. A 4 level / 2 bit signal has voltage transitions half as often as a binary signal, so the symbol rate (baud) is half the frequency of a binary signal. So in this case 250 Mbps can be transmitted at 125 Mbaud with 4 voltage levels.

The 5th level is required because the physical layer is receiving 256 data codes from the Gigabit Media Independent Interface at a rate of 8 bits (2^8 = 256) every 8ns (125 MHz). Using 4 levels across all 4 pairs of wires (4^4 = 256) would provide enough symbols to map to, but would leave no room for control signals (Start, End, Idle) or error checking/redundancy. By using a 5 level system across those 4 pairs (5^4 = 625) you end up with enough symbols for 100% redundancy in the data and an additional 113 symbols to use for control signals.

The 5th level of signaling does have one drawback though as it caused a 6dB loss, so they opted to use the redundant symbol states to implement error correction coding to try to recover it. Forward Error Correction (FEC) using a 4-Dimentional 8-state TCM (which increased the distance between points on the constellation) was used to recover the loss when there is a low signal-to-noise ratio or high amount of crosstalk (this is then decoded using a Viterbi decoder on the receiving end). The recovery of that 6dB with a DSP gives the 5 level 1000Base-TX signal the same noise immunity as a 3 level signal.

Through the use of this combination (known as 4D/PAM-5) 8 bits of data are converted to one transmission of four quinary (base-5) symbols. This is again scrambled using a side-stream scrambler as was done with 100Base-TX. Also because of the scrambling, even though we’re using 4 wires in close proximity, the crosstalk is not correlated to the data being sent, thus helping the receiver distinguish the signal from the background noise. So following Shannon again (and remembering that the 5th level is only used for synchronization of the signal so it doesn’t count in the calculations) the required bandwidth is 62.5 MHz. In real life (not theory) the 1000Base-T protocol needs about 80 MHz (and is filtered to within it) so the IEEE maintained the testing up to 100 MHz (as was the norm at the time for Cat-5 cable). They also recommended some additional tests be performed (TSB95, later amended to ANSI/TIA/EIA-568-B.1-2001 as Annex D) on the Cat-5 cable to ensure it met the requirements for return loss and ELFEXT.

As you can see there is a lot more to it than just passing n bits down the line at a specified frequency. It’s pretty amazing when you think about it, due to engineering advances and the associated improved performance available in today’s chipsets, a 500 MHz Cat-6a cable (they test to 625 MHz so there is lots of room) can support 10,000 Mbps of throughput when used with 10GBase-T (which in case you were wondering uses a THP pre-compensation of PAM with 16 levels that are then encoded in a 128 point double square constellation, aka DSQ12

. Yikes!

Andrew

P.S. Hopefully someone actually reads all of that, I can be fairly long winded – hope it made sense and maybe you learned something too.

tech-airman

T88 wrote:

I just took the study Exam 1 test available on Cisco website.

According to the results of my test Cat5 cable cannot run at the speed of 1GB.

The Odom book says it can run at 1GB. I belive to book to be right and the test to be wrong but I wanted to hear what other thought.

T88,

To finally directly answer your question, according to the "Dictionary of Internetworking Terms and Acronyms" it states "Category 5 cabling - One of five grades of UTP cabling described in the EIA/TIA-568 standard. Category 5 cabling can transmit data at speeds up to 100 Mbps...." Since 1 Gbps is greater than 100 Mbps, by definition Category 5 cabling is not able to carry 1 Gbps traffic.

Source:

Dictionary of Internetworking Terms and Acronyms - Cisco Systems - http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/c12.pdf

astorrs

tech-airman wrote:

To finally directly answer your question, according to the "Dictionary of Internetworking Terms and Acronyms" it states "Category 5 cabling - One of five grades of UTP cabling described in the EIA/TIA -586 standard. Category 5 cabling can transmit data at speeds up to 100 Mbps...." Since 1 Gbps is greater than 100 Mbps, by definition Category 5 cabling is not able to carry 1 Gbps traffic.

I think we can agree to disagree and leave it at that don't you think?

Cisco's Statement of Direction on "1000BASE-T—Delivering Gigabit Intelligence on Copper Infrastructure"
http://www.cisco.com/warp/public/cc/techno/lnty/etty/ggetty/tech/1000b_sd.pdf

dynamik

astorrs wrote:

I think we can agree to disagree and leave it at that don't you think?

Aww.. I think it's nice you guys have a hobby

LBC90805

tech-airman wrote:

T88 wrote:

I just took the study Exam 1 test available on Cisco website.

According to the results of my test Cat5 cable cannot run at the speed of 1GB.

The Odom book says it can run at 1GB. I belive to book to be right and the test to be wrong but I wanted to hear what other thought.

T88,

Category 3 cabling is designed and certified for 10 Mbps performance. Category 5 cabling is designed and certified for 100 Mbps performance. By design, you should be using Category 6 cabling for 1 Gbps performance. In other words, for each Category level, there's a corresponding intended speed for it.

For a cable or channel to be certified for a certain category level, there are required tests to be passed. Only if all tests pass can the cable or channel be certified as Cat # rating. Generally speaking, Cat 3 has less tests to pass than Cat 5, Cat 5 has less tests to pass than Cat5e, and Cat5e has less tests to pass than Cat 6. It is because of these tests that must be passed to be certified which is what makes certified Cat 6 cabling more expensive than Cat 5e, Cat 5, and Cat 3. It is because of that expense that some people are deciding to use the cheaper Cat 5 cabling and take their chances that it supports 1 Gbps speeds than to do the correct thing and use Cat 6 cabling for ther Gigabit links.

So yes, from a standard, design, and engineering perspective, Cat 5 cabling is designed for 100 Mbps performance but NOT 1 Gbps performance. So I say that the book is wrong to be teaching you something that is in violation of the standard that the Category system is based on and the test is right from the point of view of the actual Category 5 standard which is intended for 100 Mbps performance.

So in essence if I contracted AVAYA to put in 1Gbps cabling in my building they would automatically use Cat 6 cabling?

They just ripped out the old Cat 5 on the second floor of the building I work at for a new Call Center. Everything will be running at 1Gbps but they are still using Cat 5e for the installation. Funny thing is they don't even test the lines when they are installed. The cable guys for the company I work for just install the cables and then run patch cables from the panels to the switches. No certifying or anything along those lines. I know they couldn't get away with that in the real world. What is even funnier is I work for the US's biggest Telco... If you can figure out who that is?

Paul Boz

LBC90805 - The telco that I used to work for does a lot of business with the telco I presume you work for and what you describe doesn't seem out of the norm at all

scheistermeister

I didn't read it all but is this battle still raging on or has there been a victor?

astorrs

scheistermeister wrote:

I didn't read it all but is this battle still raging on or has there been a victor?

Now where is that poll option...