Interfaces and cables
Ethernet
collection of network protocol/standards
RJ45 - Registered Jack - used at the end of copper ethernet cable (UTP)
Why network protocols?
agreed upon system of communicating
to make the switch and cable manufacturer to agree upon the size and shape of the connector and port
all vendors follow industry standards
physical standards - connectors and cables
logical standards - internet protocol (IP)
Bits and bytes
1 byte = 8 bits
speed is measured in bits/second (mbps-megabits/s, not bytes)
data in hard-drive is measured in bytes
UTP Cables
Unshielded Twisted Pair
copper cables used in ethernet standards
4 pairs of cables twisted together
uses separate wire pairs "within the cable" to transmit and receive data
no metallic shield
vulnerable to electrical interference
Ethernet standards (copper)
Speed | Common name | IEEE standard | Informal name |
---|---|---|---|
10mbps | Ethernet | 802.3i | 10BASE-T |
100mbps | Fast ethernet | 802.3u | 100BASE-T |
1gbps | Gigabit ethernet | 802.3ab | 1000BASE-T |
10gbps | 10 gig ethernet | 802.3an | 10GBASE-T |
BASE - baseband signalling T - twisted pair cabling (max length = 100m) twists helps protect from Electro Magnetic Interference (EMI)
10BASE-T, 100BASE-T
uses 2 pairs - 4 wires
Scenario 1: connection between PC/router/firewall and switch
PC/firewall/routers Transmit (TX) data on pins 1&2 and Receive (RX) data on pins 3&6
Switches Receive (RX) data on pins 1&2 and Transmit (TX) data on pins 3&6
Straight-through cable - used when connecting devices which use opposite pin pairs to transmit and receive data
Full-duplex transmission - both devices can send and receive data at the same time with no collisions
Scenario 2: connection between router&router or switch&switch or router&PC
Crossover cable - used when connecting devices which use same pin pairs to transmit and receive data
pins 1&2 of device A are connected to pins 3&6 of device B
pins 3&6 of device A are connected to pins 1&2 of device B
Auto MDI-X
allows devices to automatically detect which pins their neighbor is transmitting data on, and then adjust which pins they use to transmit and receive data
unless working with old equipment, need not worry about straight-through or crossover cables
1000BASE-T, 10GBASE-T
uses 4 pairs - 8 wires
each pair is bidirectional (no specific pins for transmitting and receiving), thus can operate at much higher speeds
apart from already used pins, pins 4&5, 7&8 are connected straight
Fiber optic connections
Fiber optic cables send light over glass fibers, rather than electrical signal over copper wires
SFP (Small Form-factor Pluggable) transceiver is connected to switches or routers
fiber optic cables connect to these transceivers
there are 2 connectors on each end, one to transmit and another to receive data
unlike copper UTP cables which use wire pairs within the cable, fiber optic cables use separate cables to transmit and receive
Transmit (Tx) pin on A connects to Receive (Rx) pin on B and vice versa.
Structure of fiber optic cable
fiberglass (core)
cladding (reflects light)
protective buffer
outer jacket
Types of fiber optics
Multi-mode fiber cables
core diameter is wider
allows multiple angles (modes) of light waves to enter the fiberglass core
allows longer cables than UTP, but shorter than single-mode fiber
cheaper than single-mode fiber (due to cheaper LED-based SFP transmitters)
Single-mode fiber cables
core diameter is narrower
light enters at a single angle (mode) from a laser-based transmitter
allows longer cables than UTP and multi-mode fiber
more expensive because it uses laser-based SFP transmitters)
Fiber optic cable standards
Informal name | IEEE standard | Speed | Cable type | Max length |
---|---|---|---|---|
1000BASE-LX | 802.3z | 1gbps | multi or single mode | 550m(MM) 5km(SM) |
10GBASE-SR | 802.3ae | 10gbps | multi mode | 400m |
10GBASE-LR | 802.3ae | 10gbps | single mode | 10km |
10GBASE-ER | 802.3ae | 10gbps | single mode | 30km |
extra note
Most hosts do not have the capability to connect to a switch via fiber cabling, and most switches do not have enough SFP interfaces to support many end hosts. UTP cables are the standard for wired connections to switches. Switches typically have many RJ45 ports for end hosts to connect to via UTP cable, and then connect to a router with the SFP fiber optic port.
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