1.2 Explain the characteristics of network topologies and network types.

Question 1

Network Topologies

Answer 1

• Useful in planning a new network
  – Physical layout of a building or campus
• Assists in understanding signal flow
  – Troubleshooting problems

Question 2

Star

Answer 2

• Hub and spoke
• Used in most large and small networks
• All devices are connected to a central device
• Switched Ethernet networks
  The switch is in the middle

Question 3

Ring

Answer 3

• Used in many popular topologies
  – Token Ring is no longer with us
• Still used in many Metro Area Networks (MANs) and
  Wide Area Networks (WANs)
  – Dual-rings
  – Built-in fault tolerance

!!! for the test they always mean FDDI ring. So think Redundancy. Ring = Redundant !!!

Question 4

Bus

Answer 4

• Early local area networks
  – Coaxial cable was the bus
• Simple, but prone to errors
  – One break in the link disabled the entire network
• Controller Area Network
  – CAN bus

Question 5

Mesh

Answer 5

• Multiple links to the same place
  – Fully connected
  – Partially connected
• Redundancy, fault-tolerance, load balancing
• Used in wide area networks (WANs)
  – Fully meshed and partially meshed

Question 6

Hybrid

Answer 6

• A combination of one or more physical topologies
  – Most networks are a hybrid

Question 7

Wireless topologies

Answer 7

Infrastructure
– All devices communicate through
an access point
– The most common wireless
communication mode
* Ad hoc networking
– No preexisting infrastructure
– Devices communication amongst themselves
* Mesh
– Ad hoc devices work together
to form a mesh “cloud”
– Self form and self heal

Question 8

Peer-to-peer

Answer 8

• All devices are both clients and servers
  – Everyone talks to everyone
• Advantages
  – Easy to deploy, Low cost
• Disadvantages
  – Difficult to administer
  – Difficult to secure

Question 9

Client-server

Answer 9

• Central server
  – Clients talk to the server
• No client-to-client communication
• Advantages
  – Performance, administration
• Disadvantages
  – Cost, complexity

Question 10

LAN - Local Area Network

Answer 10

• A building or group of buildings
  – High-speed connectivity
• Ethernet and 802.11 wireless
  – Any slower and it isn’t “local”

Question 11

MAN - Metropolitan Area Network

Answer 11

• A network in your city
  – Larger than a LAN, often smaller than a WAN
• Common to see government ownership
  – They “own” the right-of-way

Question 12

WAN - Wide Area Network

Answer 12

• Generally connects LANs across a distance
  – And generally much slower than the LAN
• Many different WAN technologies
  – Point-to-point serial, MPLS, etc.
  – Terrestrial and non-terrestrial
  Cus

Question 13

WLAN - Wireless LAN

Answer 13

• 802.11 technologies
• Mobility within a building or geographic area
• Expand coverage with additional access points

Question 14

PAN - Personal Area Network

Answer 14

• Your own private network
  – Bluetooth, IR, NFC
• Automobile
  – Audio output
  – Integrate with phone
• Mobile phone
  – Wireless headset
• Health
  – Workout telemetry, daily reports

Question 15

CAN - Campus Area Network

Answer 15

• Corporate Area Network
• Limited geographical area
  – A group of buildings
• LAN technologies
  – Fiber connected, high speed Ethernet
• Your fiber in the ground
  – No third-party provider

Question 16

NAS vs. SAN

Answer 16

• Network Attached Storage (NAS)
  – Connect to a shared storage device
  across the network
  – File-level access
• Storage Area Network (SAN)
  – Looks and feels like a local storage device
  – Block-level access
  – Very efficient reading and writing
• Requires a lot of bandwidth
  – May use an isolated network and
  high-speed network

Question 17

MPLS

Answer 17

• Learning from ATM and Frame Relay
• Packets through the WAN have a label
  – Routing decisions are easy
• Any transport medium, any protocol inside
  – IP packets, ATM cells, Ethernet frames
  – OSI layer 2.5 (!)
• Increasingly common WAN technology
  – Ready-to-network

Question 18

MPLS pushing and popping

Answer 18

• Labels are “pushed” onto packets as they enter the MPLS cloud
• Labels are “popped” off on the way out

Question 19

mGRE

Answer 19

• Multipoint Generic Router Encapsulation
  – Used extensively for Dynamic Multipoint VPN (DMVPN)
  – Common on Cisco routers
• Your VPN builds itself
  – Remote sites communicate to each other
• Tunnels are built dynamically, on-demand
  A dynamic mesh

Question 20

SD-WAN

Answer 20

• Software Defined Networking in a Wide Area Network
  – A WAN built for the cloud
• The data center used to be in one place
  – The cloud has changed everything
• Cloud-based applications communicate directly to the cloud
  – No need to hop through a central point

Question 21

Demarcation point

Answer 21

• The point where you connect with the outside world
  – WAN provider
  – Internet service provider
  – The demarc
• Used everywhere
  – Even at home
• Central location in a building
  – Usually a network interface device
  – Can be as simple as an RJ-45 connection
• You connect your CPE
  – Customer premises equipment or “customer prem”

Question 22

Smartjack

Answer 22

• Network interface unit (NIU)
  – The device that determines the demarc
  – Network Interface Device,
  Telephone Network Interface
• Smartjack
  – More than just a simple interface
  – Can be a circuit card in a chassis
• Built-in diagnostics
  – Loopback tests
• Alarm indicators
  – Configuration, status

Question 23

Virtual networks

Answer 23

• Server farm with 100 individual computers
  – It’s a big farm
• All servers are connected with enterprise
  switches and routers
  – With redundancy
• Migrate 100 physical servers to one physical server
  – With 100 virtual servers inside
• What happens to the network?

Question 24

Network function virtualization (NFV)

Answer 24

• Replace physical network devices with virtual versions
  – Manage from the hypervisor
• Same functionality as a physical device
  – Routing, switching, load balancing, firewalls, etc.
• Quickly and easily deploy network functions
  – Click and deploy from the hypervisor
• Many different deployment options
  – Virtual machine, container,
  fault tolerance, etc.

Question 25

The hypervisor

Answer 25

• Virtual Machine Manager
  – Manages the virtual platform and guest
  operating systems
• Hardware management
  – CPU, networking, security
• Single console control
  – One pane of glass

Question 26

vSwitch

Answer 26

• Virtual switch
  – Move the physical switch into the virtual environment
• Functionality is similar to a physical switch
  – Forwarding options, link aggregation,
  port mirroring, NetFlow
• Deploy from the hypervisor
  – Automate with orchestration

Question 27

Virtual Network Interface Card (vNIC)

Answer 27

• A virtual machine needs a network interface
  – A vNIC
• Configured and connected through the hypervisor
  – Enable additional features
  – VLAN, aggregation, multiple interfaces

Question 28

Provider Links: Satellite networking

Answer 28

• Communication to a satellite
  – Non-terrestrial communication
• High cost relative to terrestrial networking
  – 50 Mbit/s down, 3 Mbit/s up are common
  – Remote sites, difficult-to-network sites
• High latency
  – 250 ms up, 250 ms down
• High frequencies - 2 GHz
  – Line of sight, rain fade

Question 29

Provider Links: Copper

Answer 29

• Extensive installations
  – Relatively inexpensive,
  – Easy to install and maintain
• Limited bandwidth availability
  – Physics limits electrical signals through copper
• Wide area networks
  – Cable modem, DSL, T1/T3 local loop
• Often combined with fiber
  – Copper on the local loop,
  fiber in the backbone

Question 30

Provider Links: DSL

Answer 30

• ADSL (Asymmetric Digital Subscriber Line)
  – Uses telephone lines
• Download speed is faster than the upload speed
  (asymmetric)
  – ~10,000 foot limitation from the central office (CO)
  – 200 Mbit/s downstream / 20 Mbit/s upstream
  are common
  – Faster speeds may be possible if closer to the CO

Question 31

Provider Links: Cable broadband

Answer 31

• Broadband
  – Transmission across multiple frequencies
  – Different traffic types
• Data on the “cable” network
  – DOCSIS (Data Over Cable Service Interface
  Specification)
• High-speed networking
  – 50 Mbits/s through 1,000+ Mbit/s are common
• Multiple services
  – Data, voice, video

Question 32

Provider Links: Fiber

Answer 32

• High speed data communication
  – Frequencies of light
• Higher installation cost than copper
  – Equipment is more costly and more difficult to repair
  – Communicate over long distances
• Large installation in the WAN core
  – Supports very high data rates
  – SONET, wavelength division multiplexing
• Fiber is slowly approaching the premises
  – Business and home use

Question 33

Provider Links: Metro Ethernet

Answer 33

• Metro-E
  – Metropolitan-area network
  – A contained regional area
• Connect your sites with Ethernet
  – A common standard
• The provider network is optical
  – Local fiber network
  – Wavelength-division multiplexing
  – High speed, multiple wavelengths of light