Network Switching Methods

Switching

• Switching is a logical network topology component
• Switching determines connection creation between nodes
• Three methods exist: Circuit switching, Packet switching, and Multiprotocol label switching

Circuit Switching

• A connection is established between two network nodes before transmitting data
• It uses dedicated bandwidth
• Data follows the same initial path selected by the switch
• It monopolizes bandwidth while connected, which can be a resource waste
• Common applications include live audio, videoconferencing and traditional telephone calls

Packet Switching

• Packet switching is the most popular method
• Packet switching breaks data into packets before transporting
• Packets travel any network path to the destination
• Packets find the fastest circuit available at any instant
• Packets need not follow each other or arrive in sequence
• Packets are reassembled at the destination
• Packet switching requires speedy connections for live audio and video transmission

Multiprotocol Label Switching (MPLS)

• MPLS enables multiple types of Layer 3 protocols
• These protocols travel over any one of several Layer 2 protocols
• MPLS most often supports IP
• Layer 2 WAN protocols are in common use
• MPLS offers potentially faster data transmission than packet- or circuit-switched networks

Ethernet

• Ethernet is the most popular networking technology that is used on modern LANs
• Ethernet offers benefits such as flexibility, support for various network media, excellent throughput, and a reasonable cost
• All Ethernet variations share a common access method which is CSMA/CD

CSMA/CD (Carrier Sense Multiple Access with Collision Detection)

• CSMA/CD is a network access method
• It controls how nodes access a communications channel
• It is necessary to share finite bandwidth
• Carrier Sense is an Ethernet NIC listening and waiting until no other nodes are transmitting data
• Multiple Access refers to several nodes accessing the same network media.
• Collision Detection refers to what happens when two nodes attempt a transmission at the same time

CSMA/CD Collision Considerations

• A collision happens if two nodes simultaneously check a channel, determines it is free, and begin transmission
• Collision detection is how nodes respond to a collision
• Collision detection requires a routine that is enacted if a node detects a collision
• Jamming occurs when a NIC issues a 32-bit sequence, which indicates the previous message was faulty

Ethernet Standards for Copper Cable

• IEEE Physical layer standards specify how signals transmit to media
• Ethernet standards for copper cables differ significantly in signal encoding
• Signal encoding affects maximum throughput, segment length, and wiring requirements

10Base-T

• In 10Base-T, 10 represents a maximum throughput of 10 Mbps
• Base indicates baseband transmission
• T stands for twisted pair
• It uses two pairs of wires to transmit and receive, allowing for full-duplex transmission
• 10Base-T follows the 5-4-3 rule of networking
• It contains five network segments, four repeating devices, and a maximum of three populated segments

100Base-T (Fast Ethernet)

• 100Base-T shares similarities with 10Base-T
• 100Base-T utilizes baseband transmission, star topology, and RJ-45 connectors
• 100Base-T supports a maximum of three network segments
• It connects using two repeating devices
• 100Base-T has a 100 meter segment length limit between nodes

1000Base-T (Gigabit Ethernet)

• In 1000Base-T, 1000 represents 1000 Mbps
• Base indicates baseband transmission
• T indicates twisted pair wiring
• 1000Base-T utilizes four pairs of wires in Cat 5 or higher cable to transmit and receive signals
• The maximum segment length is 100 meters with one repeater

10GBase-T

• 10GBase-T pushes the limits of twisted pair cables
• It requires Cat 6, 6a, or 7 cabling
• The maximum segment length is 100 meters
• 10GBase-T offers very fast data transmission and is cheaper than fiber-optic
• 10GBase-T is used to connect network devices, servers, and workstations to a LAN

100Base-FX (Fast Ethernet) for Fiber-Optic Cable

• 100Base-FX has a 100-Mbps throughput, baseband, fiber-optic cabling
• A multimode fiber that consists of at least two strands
• Half-duplex mode transmits and receives on one strand, with a 412 meter segment length
• Full duplex-mode sends and receive on both strands and contains a 2000 meters segment length
• There is one repeater maximum

1000Base-LX (1-Gigabit Ethernet) for Fiber-Optic Cable

• The 1000 in 1000Base-LX represents 1000-Mbps throughput
• Base stands for baseband transmission
• LX relies on 1300 nanometers wavelengths
• It contains longer reach than any other 1-gigabit technology
• A single-mode fiber maximum segment is 5000 meters
• A multimode fiber maximum segment is 550 meters
• One repeater between segments is allowed
• It is an excellent choice for long backbones

1000Base-SX (1-Gigabit Ethernet) for Fiber-Optic Cable

• The difference between 1000Base-LX and 1000Base-SX is 1000Base-SX uses multimode fiber-optic cable which makes installation less expensive
• 1000Base-SX also uses short wavelengths (850 nanometers)
• The maximum segment length depends on fiber diameter and modal bandwidth

1000Base-SX continued

• Modal bandwidth measurement is the highest frequency of multimode fiber signal (over a specific distance)
• 50 micron fibers: 550 meter maximum length
• 62.5 micron fibers: 275 meter maximum length
• One repeater between segments
• Best suited for shorter network runs

10-Gigabit Fiber-Optic Standards

• Fiber-optic cable is extraordinary with pushing limits
• 802.3ae standard: Fiber-optic Ethernet networks that are transmitting data at 10 Gbps comes in several variations
• Common characteristics are star topology and full-duplex mode that allows one repeater
• The difference is signal’s light wavelength and maximum allowable segment length

10GBase-SR and 10GBase-SW

• 10G: 10 Gbps
• Base is a baseband transmission
• S stands for short reach
• Physical layer encoding uses R with LAN fiber connections and W with SONET fiber connections
• Multimode fiber 850 nanometer signal transmission and depends on fiber diameter of maximum segment length

10GBase-LR and 10GBase-LW

• 10G: 10 Gbps
• Base: baseband transmission
• L: long reach
• Uses single-mode fiber: 1310 nanometer signal transmission
• Maximum segment length: 10,000 meters
• 10GBase-LR: WAN or MAN
• 10GBase-LW: SONET WAN links

10GBase-ER and 10GBase-EW

• E: extended reach
• Single-mode fiber transmit signals with 1550 nanometer wavelengths
• It is the longest fiber-optic segment reach: 40,000 meters (25 miles)
• Best suited for WAN use

Ethernet Frames

• Ethernet comes in four types
• Ethernet_802.2 (Raw)
• Ethernet_802.3 (Novell proprietary)
• Ethernet II (DIX)
• Ethernet_SNAP
• Frame types differ slightly

Using and Configuring Frames

• Ensure all devices use the same, correct frame type to facilitate node communication
• Ethernet_II currently used today
• Frame type configuration is specified using NIC configuration software and NIC autodetect
• Importance is to know frame type for troubleshooting

Frame Fields

• Common fields include a 7-byte preamble and a 1-byte start-of-frame delimiter
• SFD (start-of-frame delimiter) identifies where data field begins
• Fields also include a 14-byte header and a 4-byte FCS (frame check sequence)
• The frame size range is 64 to 1518 total bytes
• Larger frame sizes result in faster throughput

Ethernet_II (DIX)

• Developed by DEC, Intel, Xerox (abbreviated DIX)
• Contains 2-byte type field to identify the Network layer protocol
• Most commonly used on contemporary Ethernet networks

PoE (Power over Ethernet)

• PoE supplies electrical power over Ethernet connections
• Two device types: devices that supply power (PSE) and devices that receive power from the PSE (PDs)
• Requires Cat 5 or better copper cable
• Connectivity devices must support PoE

Summary

• Switching manages packet filtering and forwarding
• Ethernet manages cabling specifications, data frames, and PoE