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What is the maximum and/or ideal length of an ethernet cable? Is there a distance that data cannot be transferred over an ethernet cable, say over X number of feet?
studiohack
Posted 2010-09-25T15:54:05.910
Reputation: 13 125
Maximum/ ideal length of ethernet cable?
Answers
16
There is no ideal length of a cat 5 cable but the specification states that it should not be more than 100m (328 feet).
More info on the wiki page
The specification of 328 feet has to do entirely with collision detection in a CSMA/CD (Carrier Sense Multi Access / Collision Detection network. Basically, the length is limited by the fact that the shortest possible frame size (64 bytes) can be sent out on the wire and if a collision occurs, the sending node will still be sending that frame when it hears the collision (due to a jam signal or higher than normal amplitude). If a collision occurs during the first 64 bytes of a frame, this is a normal collision. If something is out of spec such as the cabling is too long and the collision occurs after the first 64 bytes, this is a late collision and will not be retransmitted until an upper layer of the OSI model detects that the packet did not make it to its destination. You can run longer cabling and the network will still function, but there will be issues.
Nifle
Posted 2010-09-25T15:54:05.910
Reputation: 31 337
1The statement "the length is limited by the fact that the shortest possible frame size (64 bytes) can be sent out on the wire and if a collision occurs" applies in gigabit networks but is not true for 10/100 networks. The speed of a signal in copper cables = 200,000,000 m/s. 64 bytes = 512 bits. (200,000,000[m/s]/100,000,000[bits/s]) * 512[bits] = 1024 meters (or 512 meter round trip) maxim distance to detect collisions during a 64 bit packet. – Keith Reynolds – 2015-08-19T19:48:44.973
Before there were network switches, hubs would repeat signals which along with round trip propagation delay is the reason for the 543 rule. that you can have a maximum 5 network segments daisy chained with 4 repeaters, and 3 mixed networks, though the mixed network rule does not apply to twisted pair. Furthermore, switched networks buffer and queue packets which removes even the 543 restriction. – Keith Reynolds – 2015-08-19T20:04:39.060
Instead the main limiting factor is a cable's impedance, which attenuates the signal, and a Network cards (NIC) ability to differentiate between high and low signals at the other end. the specs specify 100 meters, but with quality cable that have lower impedence and good termination with minimal cros talk or alien talk, two NICS can sometimes communicate well over cables longer than 100M – Keith Reynolds – 2015-08-19T20:06:48.570
1True, if the cable is used for ethernet (which is very likely, of course). The maximum length of 100 meter ensures that collision detection mechanisms work as expected (and maybe also ensures the signal strength is okay?). – Arjan – 2010-09-25T16:23:37.453
Category-5 cabling was de-registered last century. The only currently registered cable categories are 3, 5e, 6, and 6a. – Ron Maupin – 2018-07-29T17:26:07.963
9
The ideal length is exactly as long as you need (up to 100 meters) and no longer. Every extra 11.9 inches adds another nanosecond of extra latency.
Joel Coehoorn
Posted 2010-09-25T15:54:05.910
Reputation: 26 787
Signals travel down copper wire at about 200,000,000 meters a second that is approximately 656168000 feet or 1.524 nano seconds a foot. – Keith Reynolds – 2015-08-19T20:31:23.387
While latency is important to network performance, it is not a limiting factor in determine a 100 m specification. – Keith Reynolds – 2015-08-19T20:32:29.057
16I just swapped out my 25' cable for a 10' cable here at home. Those extra 15 nanoseconds are going to help me to be the first answerer on Stack Overflow. Thanks for the suggestion, Joel! – James McNellis – 2010-09-25T19:38:05.530
3
What is the maximum and/or ideal length of an ethernet cable? Is there a distance that data cannot be transferred over an ethernet cable, say over X number of feet?
Your question is really too broad. Different ethernet standards use different media with different lengths.
Some ethernet standards and the cable length limits:
10BASE-5 500 meters
10BASE-2 185 meters
10BROAD-36 3600 meters
10BASE-T 100 meters
10BASE-FL 2000 meters
10BASE-FB 2000 meters
10BASE-FP 500 meters
100BASE-TX 100 meters
100BASE-T4 100 meters
100BASE-FX 2000 meters
100BASE-SX 300 meters
100BASE-LX10 10000 meters
1000BASE-T 100 meters
1000BASE‑CX 25 meters
1000BASE‑KX 1 meter
1000BASE‑SX 220, 275, or 550 meters
1000BASE‑LX 550 or 5000 meters
1000BASE‑LX10 10000 meters
1000BASE‑EX 40000 meters
1000BASE‑ZX 70000 meters
1000BASE‑BX10 10000 meters
1000BASE-T1 15 meters
1000BASE‑TX 100 meters
1000BASE-RHx 15 to 50 meters
10GBASE-T 100 meters
10GBASE-SR 300 or 400 meters
10GBASE-LR 10000 meters
10GBASE-ER 40000 meters
10GBASE-ZR 80000 meters
10GBASE-LX4 300 or 10000 meters
10GBASE-LRM 220 meters
10GBASE-CX4 15 meters
10GBASE-KX4 1 meter
10GBASE-KR 1 meter
10GBASE-PR 20000 meters
There are other ethernet standards with other cable length limits. Some cabling has other requirements, too. For example, UTP cabling has a limit of 100 meters, assuming 90 meters of solid-core, horizontal cable (better performance, but more fragile) and a maximum 10 meters of stranded patch cable (worse performance, but less fragile) split between both ends.
There are also different grades of fiber cabling, and some ethernet standards can be used at different distances, depending on the fiber grade, while others require a specific grade of fiber.
Ron Maupin
Posted 2010-09-25T15:54:05.910
Reputation: 3 130
3
Ideal: As short as possible, as isolated as possible.
Maximum: 100 meters without repeaters.
Grumpy ol' Bear
Posted 2010-09-25T15:54:05.910
Reputation: 5 313
1
To be in spec, a CAT 5 UTP cable should not exceed 100 meters. Cable can be connected with repeaters and you can get another 100 meters and so on. However, if you network is too large, then the TCP/IP packet will take so long to go from end to end computers will reach the timeout before they get a reply back. At that point other devices will have to be used to retransmit the packets, like switches/routers... I'm not sure about that distance/time before packets are considered lost.
Scott McClenning
Posted 2010-09-25T15:54:05.910
Reputation: 3 519
5I truly doubt the maximum length is about timeouts. I've always learned it's to ensure proper collision detection. (Timeouts limits are much, much longer than the microseconds used for collision detection.) – Arjan – 2010-09-25T16:25:47.373
Category-5 cabling was de-registered last century and there is actually no such thing for the last 20 years. The only currently registered cable categories are 3, 5e, 6, 6a, and now 8, which is shielded and limited to 30 total meters. – Ron Maupin – 2019-03-20T02:51:10.620
-1
Maximum length of Ethernet over CAT5 has very interesting information.
TL;DR:
- the maximum for ethernet is actually 2500m (or up to 5500m), to avoid crosstalk
- the 100m (90m horizontal + 10m server patches) is set to limit the loss of signal strength so that a cable can still be certified as cat 5a
serv-inc
Posted 2010-09-25T15:54:05.910
Reputation: 400
Category-5 cabling has been deprecated since the last century. The only currently recognized cable categories are 3, 5e, 6, and 6a. – Ron Maupin – 2018-07-21T19:00:32.023
3As far as ideal length. The ideal length would be as long as necessary and no longer. Be it for cost, interference, cable management or latency (for all the hard core gamers out there). Excess unneeded cable can cause problems. – Scott McClenning – 2010-09-25T23:03:56.707
That depends. Ethernet can run on fiber for many, many kilometers. Ethernet runs on a variety of media (coax, UTP, fiber, etc.), and there are multiple ethernet standards for each medium with varying maximum distances. You would need to be specific about the medium in question and the ethernet standard used on that medium. – Ron Maupin – 2018-07-21T18:57:37.340
1There is also a MINIMUM length, to avoid problems like reflection. I encountered this years ago, when I was doing up my house. I cn't remember the value, but I THINK a cable one foot long was not recommended! – None – 2011-06-21T08:58:35.343
1which is odd, as we've got some 10cm patch cables in our server room/switch bays. – tombull89 – 2011-06-21T09:36:34.033