Networking may be straightforward, but the world of networking terminology is not. I’ve been steeped in the strange lingo of Ethernet for many years, but I still get confused by some of the terms. What’s the difference between 1000BASE-CX, 1000BASE-SX, and 1000BASE-T? In this post, I’m going to tackle this Ethernet network naming convention.
Let’s get the first two components of the network name out of the way:
The first part is the signaling rate in megabits per second. In layman’s terms, this is the speed of the network at hand. You are likely to come across one of the following:
- 10 megabits
- 100 megabits – Fast Ethernet
- 1000 megabits – Gigabit Ethernet, GbE, or 1000BASE-X
- 10,000 megabits – 10 Gigabit Ethernet, 10GbE, or 10GBASE-X
- 40,000 megabits – 40 Gigabit Ethernet, 40GbE, or 40GBASE-X
- 100,000 megabits – 100 Gigabit Ethernet, 100GbE, or 100GBASE-X
It may strike you as odd that the next part is always the word, “BASE”. But there is a reason for this, too. BASE refers “baseband”, meaning that this is an unfiltered line not requiring a digital modulation scheme. Back in the day, there was a 10PASS-TS version of Ethernet that used a signaling scheme similar to a modem, but baseband is dominant today.
So 100BASE refers to a Fast Ethernet connection that uses the unfiltered cable for transmission.
The third part of an Ethernet network type refers to the cabling used to carry the signals. The earliest forms of Ethernet used coaxial cable, but thin twisted-pair cabling became popular in the mid-1990s. Faster versions of Ethernet also often use fiber optics rather than electrical signals.
There are a bewildering assortment of physical interconnects for Ethernet. But the naming system isn’t as complex as it might appear:
- The first letter tells us which kind of wire we are talking about:
- “T” means twisted-pair cable (e.g. the common Cat5 in use today)
- “K” means a copper backplane
- “C” means balanced copper cable
- “F” means optical cable
- “B” uses two wavelengths over a single optical cable
- “S” means short-range multi-mode optical cable (less than 100 m)
- “L” means long-range single- or multi-mode optical cable (100 m to 10 km)
- “E” means extended-range optical cable (10 km to 40 km)
- “Z” means long-range single-mode cable at a higher wavelength
- Next is the coding scheme for data on the wire
- “X” means 4B/5B block coding for Fast Ethernet or 8B/10B block coding for Gigabit Ethernet
- “R” means 64B/66B block coding
- Finally, we have a number representing the number of parallel “lanes” for data
- “1” would mean serial (non-parallel) but is omitted instead
- “4” or “10” are available for copper wire
- Just about any other number could be used for optical lanes or wavelengths
Now let’s look at some examples:
- Back in the day, 10BASE-T became more common than coaxial 10BASE2. It was a simple 10 megabit baseband signal over common twisted-pair.
- When Fast Ethernet first rolled out, there was some concern that traditional (usually Cat3) cabling couldn’t handle 100 megabits. Some early implementations used four copper pairs (100BASE-T4) or fiber optics (100BASE-FX), but nearly every 100 megabit Ethernet connection today is 100BASE-TX, using plain two pairs on plain Cat5 cable.
- Gigabit Ethernet had a similar history. Many were concerned that two pairs on unshielded Cat5 wiring could not handle 1000 megabits per second, so optical (1000BASE-SX) and balanced shielded wiring (1000BASE-CX) were specified. Although an unshielded 2-pair standard was developed (1000BASE-TX), it never really caught on. Therefore, today’s predominant gigabit LAN connection, 1000BASE-T, uses all four pairs of unshielded twister-pair wiring on a Cat5 cable (see note 1).
- The 10 Gigabit Ethernet world has mostly shifted to the block coding scheme from Fibre Channel, 64B/66B, which is denoted by the letter “R”. This gives us a family of fiber optic cables (10GBASE-SR, LR, ER, etc), and a copper backplane interconnect (10GBASE-KR). The earlier copper wiring standard (10GBASE-CX4) used InfiniBand-like 4-lane cables and 8B/10B signaling, as did 10GBASE-KX4 on the backplane. A backwards-compatible twisted-pair 10GBASE-T has also been developed, but work continues to make it power-efficient enough to be practical (see note 2).
- Looking ahead, we see Higher-Speed Ethernet emerging: 40GBASE-KR4 for backplane use, multi-mode optical 40GBASE-SR4 and 100GBASE-SR10, and long-range single-mode optical 40GBASE-LR4 and 100GBASE-LR10.
As you can see, all this alphabet soup does have some consistency. Common unshielded twisted pair wiring is all “BASE-T”, optics are denoted according to their range (“S”, “L”, “E”), and backplanes use “K” copper. Clear as mud?
Note 1: Lots of people (and even equipment makers) incorrectly refer to common Gigabit Ethernet as “1000BASE-TX”, but this really should be called “1000BASE-T”.
Note 2: We will probably never see a 10GBASE-TX, which would use just 2 pairs of unshielded twisted pair copper wiring.
I had never heard of 10PASS-TS, interesting.
In the late 1980s there was also 10BROAD-36, which used a 6MHz channel to carry Ethernet over standard 75 Ohm coax used in CATV. BROAD referred to broadband, in that the ethernet signal was modulated onto a carrier wave of whatever TV frequency was chosen.
It got some traction in universities and other large campuses which had TV coax running between buildings. It was limited to about 2 miles, so it was never suitable for delivery from the cable company to customers. DOCSIS came along later and zipped up that market need.
I forgot about 10BROAD-36! I saw that back in college!
I think it’s interesting how history repeats itself. Each time Ethernet ratcheted up in speed, we saw UTP naysayers saying it needed fiber optics. And each time the copper UTP version came out ahead. Although 10GBASE-T is a power hog now, I’m hearing that some component makers have promising low-power parts coming soon!
I suspect a copper->optical transition will happen for economic reasons, not technical limitations of copper transceivers. Cat6 UTP is almost as expensive to install as fiber: it has a bending radius, it cannot be stapled to the walls, it is very sensitive to connectorization, it requires relatively tight manufacturing tolerances in the twists per meter of each pair and the quality of the copper, etc.
UTP has the additional problem that it is made of _copper_, which has gradually become more expensive as a raw material with little sign of improvement.
50 ft Ethernet Cable says
I have not much time, but I've got many useful things here, love it!
Jason Zhou says
Very useful information. Thanks a lot!
This helped a lot! A handy reference
Very helpful, had learned this at varsity but after 5years working experience I totally forgot how to differentiate. Thank you sir, much appreciated, and your article is on point
Gerry Persaud says
thank you very much for explaining this – your document is short and to the point