Before you start
Objectives: learn about different Ethernet standards – their speed, maximum bandwidth, type of medium which can be used, and maximum segment length.
Prerequisites: you should be familiar with Twisted Pair cable and Fiber optic cable.
Key terms: fiber, cable, ethernet, maximum, duplex, multimode, mbps, bandwidth, distance, optic, segment, transmission, medium, mode, speed, lenght, pair, twisted, standard
When we look at different Ethernet standards we look at four different things: speed, the transmission medium, distance and the number of hosts. Ethernet specifications have a common naming standard,.They all have the word base in the middle. In front there’s a number which designates thespeed, and on the back is a letter or combination of letters that designate the transmission medium. For the speed can have 10 megabits per second, 100 megabits per second (also called Fast Ethernet), 1000 megabits per second (also called gigabit Ethernet), and 10 gigabit Ethernet. For all Ethernet specifications the number of hosts is the same, it is 1024 hosts per network.
Twisted Pair Standards
When it comes to Twisted Pair transmission medium the letter T stands for twisted pair. So we have10BaseT, 100BaseTX, 1000BaseT and 10GBaseT. All four of these use Unshielded Twisted Pair cable. There’s another letter designation that’s added for the 1000 Base, and that’s CX. CX is an UTP cable that’s used in very short runs, typically within a wiring closet.
With 10BaseT we need to use CAT3 cable or higher. The bandwidth is 10 Mbps (half duplex) or 20 Mbps (full duplex).
For 100BaseTX we need to use CAT5 cable or higher. It uses two pairs of wires. The bandwidth is 100 Mbps (half duplex) or 200 Mbps (full duplex).
For 1000BaseT we need to use CAT5 cable or higher. It uses all four pairs of wires. The bandwidth is 1000 Mbps (half duplex) or 2000 Mbps (full duplex).
For 10GBaseT we need to use CAT5E cable or higher, although CAT6 or CAT7 is preferred. The bandwidth is 10 Gbps (full duplex only).
1000BaseCX (short copper)
For 1000BaseCX we need to use special copper cable (150 ohm). The bandwidth is 1000 Mbps (half duplex) or 2000 Mbps (full duplex).
As far as distance, all of the “T” designations are the same. Cable lenght can be up to 100 meters. That makes it easy to remember. The only one that’s different is the CX, which is up to 25 meters.
Fiber Optic Standards
Now let’s look at the other transmission medium that Ethernet can use, which is Fiber Optics. For Fiber Optics we have the following designations: 10BaseFL, 100baseFX, 1000BaseSX, 1000BaseLX,10GBaseSR, 10GBaseLR, 10GBaseER, and another variations of 10GBase are 10GBaseSW,10GBaseLW, 10GBaseEW. Another thing to be aware of is what type of fiber optic cable it uses. It’s either multimode fiber or single mode fiber.
With 10BaseFL we need to use fiber optic multimode cable. Maximum bandwidth is 10 Mbps. Maximum segment length is up to 2000 meters. When mixed with with FOIRL equipment, maximum segment length is limited to FOIRL’s 1000 meters.
With 100BaseFX we need to use fiber optic multimode cable. Maximum bandwidth is 100 Mbps. Maximum segment lenght is 412 meters.
With 1000BaseSX we need to use fiber optic multimode cable. Maximum bandwidth is 1000 Mbps (half duplex) or 2000 Mbps (full duplex). Depending on the cable quality, maximum segment lenght can range from 220 meters to 550 meters.
With 1000BaseLX we can use either multimode or single-mode fiber optic cable. Maximum bandwidth is 1000 Mbps (half duplex) or 2000 Mbps (full duplex). Maximum segment lenght is 550 meters (multimode) or 10 kilometers (single-mode)
With 10GBaseSR/10GBaseSW we need to use multimode fiber optic cable. Maximum bandwidth is 10 Gbps (full duplex only). Maximum segment length is 300 meters.
With 10GBaseLR/10GBaseLW we need to use single-mode fiber optic cable. Maximum bandwidth is 10 Gbps (full duplex only). Maximum segment length is 10 kilometers.
With 10GBaseER/10GBaseEW we need to use single-mode fiber optic cable. Maximum bandwidth is 10 Gbps (full duplex only). Maximum segment length is 40 kilometers.
As you noticed, the cable mode dictates the distance. Now with 10 base FL, transmission speeds are rather low, so even with a multimode fiber cable we can get between 1000 and 2000 meters for the transmission distance. Because of the increased speeds with 100Base Ethernet the distance is decreased down to 412 meters. With gigabit Ethernet 1000BaseSX we have between 220 and 550 meters. Here’s where the difference is clear. We can use multimode fiber with LX designations, but we only get about 550 meters. If we use the single mode fiber we get up to 10 kilometers in distance. For the 10G designations, the S designation is multimode. Well because it’s multimode the distance is less, and in this case the distance is about 300 meters. To help us remember all those information we should keep in mind that S stands for short, L stands for long, and the E stands for extended or extreme long. Multimode fiber has a shorter distance than the single mode fiber. So to get up to the 10 kilometer and beyond distances we will need to have single mode fiber instead of the multimode fiber. The only exception to this rule is when we’re talking about the 10BaseFL Ethernet because the speeds were so slow they could get a pretty long distance out of that multimode fiber. As the speed increases with the same fiber type, the distances will somewhat drop.
SR versus SW
With Ethernet every designation in the 10G Ethernet with a W uses what’s called SONET. SONET is a Wide Area Network technology that uses fiber optics to multiplex signals across a single wire. So instead of having a single light pulse sending information one at a time, one after another, with SONET we have multiple pulses going at the same time at different frequencies. SONET allows Ethernet to run over much longer distances and using equipment that’s already been put into place for wide area networking.
Important things about each Ethernet standard are: speed, distance, transmission medium, and the number of hosts on the network. For all Ethernet designations the number of hosts is the same, it’s 1024 hosts per network. In every specification name, the number designates the speed, and the letter at the end designates the transmission medium. So we have T for twisted pair, C for copper, F for fiber, and then also for fiber optic we have S, L and E, with each one of those roughly indicating the distance. S for short, L for long and E for extremely long. Also, whenever we see the W designation along with the fiber optic designation, that stands for Ethernet over SONET. With fiber optic cables we have multimode or single mode, with multimode being a shorter distance than the single mode. When it comes to cost, copper is typically cheaper to implement.