Chapter 5 - Wired Ethernet LANs

Chapter 5 IS 4440
Local area networks exist within a company's site. On the customer premises - office suite, office building, or other property owned by the corporation.
Wide are networks connect different sites within an organization or transmit data between organizations. Transmission beyond its premises.
Speeds of LANs
LANs bring 100 Mbps to 1 Gbps to each desktop. Shared by multiple users
Speeds of WANs
WAN speeds more typically vary from 1 Mbps to about 50 Mbps. Shared by multiple users.
Workgroup switches
Switches that connect hosts to the network.
Core switches
Switches that connect switches to other switches
Access Links
Transmission links that connect hosts to workgroup switches.
Trunk Links
Transmission links that connect switches to other switches.
metropolitan area network - type of WAN limited to a large city and its surrounding communities. Man prices per bit transmitted are lower than those of WANs with geographical scope. MAN speeds are higher than WANs but slower than LAN speeds.
Another name for Ethernet
802.3az task Group
Energy-Efficient Ethernet standards
802.3 working group
Ethernet Standards
802.1 Working Group
General Standards, including Security
802.11 Working Group
Wireless LAN Standards
IEEE Standards Association
802 LAN/MAN standards Committee
American National Standards Insitute
International Organization for Standardization
Standards of Single networks
Single networks use standards at the physical layer and the data link layer.
network interface card - implements Ethernet on a specific machine or host
Possible states in binary and digital signaling?
Binary their are two possible states. Digital signaling there are few possible states (2,4,8, etc.)
Digital signaling vs Binary Signaling
In binary signaling, there are two possible states. One bit is sent in each clock cycle. In digital signaling, there are a few possible states (2,4,8, etc.) More than one bit is sent in each clock cycle.

Binary transmission is a type of digital signaling. Not all digital signaling, however, is binary signaling.
Clock Cycle
When a device transmits, it holds the signal constant for a brief period of time.
UTP wiring
4-pair unshielded twisted pair wiring.
Serial Transmission
Transmitting over a single pair of wires
1 bit per clock cycle
Parallel Transmission
Transmission over more than a single pair of wires.
1 bit per clock cycle per wire pair
4 bits per clock cycle on 4 pairs
100 bits per clock cycle on 100 pairs

Parallel means that transmission occurs on multiple paris, not just four pairs.
Attenuation and Noise
Attenuate - signal gets weaker
Noise - random energy from other objects on the wire
cross-talk interference
generated by the other wire pairs in the same bundle.
Cable quality
is indicated by its category number
example: Category 5e (e stands for enhanced)
Category 6 or Cat 6
Cat 6A
What is the limiting factor in LAN fiber distance?
modal dispersion - modes entering the core at higher angles will take longer to travel than the straight mode. If modal dispersion is too large, parts of the light from sequential light pluses will overlap, making the signal unreadable.
Quality measurement in UTP and LAN fiber?
UTP is expressed as a category number (5e, 6 or 6A.
LAN fiber is expressed modal bandwidth (MHz-km)
Core Diameter
50 micron fiber and 62.5 micron fiber. Smaller is better. Travels faster
Wavelength vs. Amplitude
Wavelength is peak of Wave to next peak of Wave how long. Amplitude is the strength or depth of the wave.
Multimode fiber
light modes can enter at various angles. 50 or 62.5 microns are multimode fibers.
Link aggregation
two or more trunk lines to connect a single pair of switches. Networking professionals call this bonding.
Limits on distance of Ethernet on UTP or Fiber.
The 100-meter Ethernet limit for UTP and the longer distance limits for fiber only apply to physical links between pairs of devices, not to end to end data links between hosts across multiple switches.
Maximum end to end distance in Ethernet network
There is no maximum end-to-end distance (data link distance) between pairs of hosts in an Ethernet network.
MAC frame
media access control frame or the Ethernet Frame.
MAC Addresses
Ethernet addresses or called physical addresses because physical devices (NICs) implement Ethernet at the physical, MAC, and LLC layers.
Minimum length for the data field?
no minimum length but if the data field is less than 46 octets long, then a PAD field must be added to bring the total length of the data and pad fields to 46 octets.
Ethernet organization
Ethernet requires a hierarchical switch hierarchy. In a hierarchy, there is only a single possible path between any two end hosts.
Why Ethernet's dominance in LAN technology
The fact that there is only a single possible path between any two end hosts in an Ethernet hierarchy makes Ethernet switch forwarding simple and therefore inexpensive. The low cost has led to dominance in LAN technology.
Virtual LANs are groups of clients and servers that are allowed to communicate with each other but not with clients or servers on other VLANs.
What is 802.1Q
Frame tagging
Tag Control Information (TCI) field
VLAN addresses
Managed switches vs Regular switches
Managed switches are more expensive than non-managed switches, but they reduce management labor in large networks enough to more than offset managed switch purchased costs. Managed switches reduce overall costs.
Power over Ethernet
provides up to 25 watts to attached devices. USB and phones already do this.
glass core is surrounded by a thin glass cylinder called cladding
LAN Fiber
LAN Fiber Distance: 200 to 300 m, Light wavelength: 850 nano meters Type of Fiber: Multimode (thick core) Core Diameter: 50 or 62.5 microns
Primary Distance limitation: Modal dispersion Quality Metric: Modal Bandwidth (MHz-km)
Carrier WAN Fiber
WAN Fiber Distance: 1 to 40 m, Light wavelength: 1310 or 1550 nano meters Type of Fiber: Single-mode (thin core) Core Diameter: 8.3 microns
Primary Distance limitation: Absorptive attenuation Quality Metric: N/A
The Rapid Spanning Tree Protocol (RSTP)
backup link is deactivated until needed but can cause a loop. This helps prevent single points of failure in a network.