Certification IT Specialist - Certiport

Peer-To-Peer Networks

• Most home and small office networks

• No central device managing and storing users, files, and folders

• Every device is its own server b/c every device is responsible for managing access to its own resources

Client-server network

• Many medium to large sized businesses

• A central server hosts all the user accounts, devices, and permissions for the users and devices

• Active Directory is the server piece in a Windows-based client-server network

Unicast

Data is transmitted from one device to another

Multicast

One device transmits data to a selected group of devices

Broadcast

A device transmits data to every other device on its network

IoT Devices

A device that’s controlled remotely, often through a smartphone app or similar

Hypervisor

A tool that manages physical resources for virtual machines

Type II hypervisor: sits within an operating system (Windows 10 Pro)

Type I hypervisor (bare-metal): run on their own operating systems

Virtual machines

Software-based, allowing to run multiple operating systems

Virtual Switches (External, Internal, Private)

External: Gives virtual machines access to whatever the host PC has access to

Internal: Virtual machines on the switch have access to each other & the host machine

Private: Virtual machines only have access to each other

VPN

A private network that uses a public network to transmit data from a source to a destination

Site-to-Site: Two businesses/locations within a network are connected

Uses Internet Protocol Security (IPsec): A suite of protocols that authenticates and encrypts data packets over VPN

Provides confidentiality and integrity of data

Remote Desktop Connection

Where one connects to and takes over the device

Remote Assistance: Allows one to see what someone is doing when connected to a machine

Local Area Networks (LANS)

Networks that are confined to a single building or a single area of a building

Share common resources (servers, printers, workstations)

DMZ

• A perimeter network; holds devices that need to be seen by the public/private security zones of a network

• Web servers, email servers, and proxy servers

• Back-to-back Configuration: Firewall on both sides of a perimeter network

• Three-leg Perimeter: Each leg connected to a single firewall

IP Addresses

• Any IP address starting with 10, 192.168., 172.16-172.31, 127 = private IP address → can be reused, saves from public IP’s being used on every device

Automatic Private IP Addressing (APIPA)

Address range 169.254 → used when a device can’t get an IP address through a DHCP server (gives out IP addresses to devices)

Virtual LANS (VLANS)

Logically segments the network

Wired LAN

• Computers & devices that use Ethernet cables to connect to switches

• The switches connect through Ethernet cables, to one or more routers, which connect a network to other networks

Wireless LAN

• Common to homes and small offices

• Devices connect through a wireless access point (wireless router)

• More flexible than wired LANS, devices can connect to the LAN from different places within a building

• Little slower than wired LANS, more susceptible to signal interference, and less reliable for consistency in speed + performance

Wide Area Network (WANS)

• Networks that cover multiple geographical areas and are a collection of LANS

Dial-up line (not a leased line)

• A phone line & a server

• Very slow connection by today’s standards (56 Kbps)

Integrated Services Digital Network (ISDN)

• Basic Rate Interface (BRI): Uses TWO 64 Kbps channels for a speed of 128 Kbps

• Primary Rate Interface (PRI): Uses 23!!, 64 Kbps channels for a speed of 1.536 Mbps (Runs on T1 circuit line)

Security (SA)

• Generates the authentication and encryption keys used in IPsec

Authentication Header

• Provides authentication and integrity of data

Encapsulating Security Protocol (ESP)

Provides authentication, integrity, and encryption of data

T1 leased line

Uses 24, 64 Kbps channels of data + 8 Kbps for overhead = 1.544 Mbps

A dedicated leased line

T3 lines

• 44.736 Mbps = 28 T1 lines

• 672, 64 Kbps channels

E1 line

European version of the T1 line

Uses 32 64 Kbps channels, 2.048 Mbps

T3 line

16 E1 lines, 34.368 Mbps

Digital subscribe line (DSL)

A customer has a dedicated phone line from the origin to a telco office

• SDSL: Upload and download speeds are the same (used in businesses that need fast uploads

• ADSL: Used in homes and businesses, different upload/download speeds BUT download speeds > upload speeds

Cable modem

Tends to run over shared bandwidth

Speeds are slower during peak usage hours → Speeds are faster than DSL

Not on dedicated lines

Latency

The delay from a source to a destination

Standards and Characteristics

IEEE 802.11 → Runs on 2.4 GHz and 5 GHz

• 5 GHz: Faster and shorter range

Infrastructure wireless network

• One or more WAPs is the central point of the network

• SSID: name for the network

Ad Hoc wireless network

• No central wireless

• Doesn’t have the security or encryption that infrastructure has

Wireless Bridge

Used to connect two wired segments of a network

• Can serve as repeaters (boosts a signal reaching its max distance, also what a Hub does)

WAP

• Should be placed in a room centrally or above the ground

• Avoid placing it near items that can interfere with its signal (microwaves, elevator shafts, water tanks)

Star Topology

• A central device (switch) is the center of the network which all other devices connect

• Fault tolerant: A break will not affect the rest of the network only if the central device doesn’t fail

Mesh Topology

• Common in WANS, every device has a connection to every other device

• Provides redundancy

• n * (n-1) / 2

Ring Topology

• Not common in LANS, used in FDDI networks

• FDDI: fiber optic cable connects networks within a ring, typically has two rings

• One token of data is being passed at a time from device-device → avoids having collisions, if there’s a break the network is down

Bus Topology

• Every device is connected to a backbone cable that runs from one end of the network to the other → needs terminators at both ends of the cable

• Kept small in size, any break means the entire network is down (includes taking down the network to add/remove a device)

Physical Topology

• Physical appearance and setup of a network

Logical Topology

Describes how data flows through a network

Switch

Uses a MAC address table to direct traffic within a network

Learns the MAC address of every device connected

• Fast Ethernet = 100 Mbps

• Gigabit Ethernet = 1 Gbps

Have speed capabilities from 10 Mbps to 10 Gbps

Uplink (MDI) Ports

• To connect switch to switch

• Faster than other ports + Handles straight-through and crossover cables

Managed/Unmanaged Switches

• Managed: Can be configured, have an IP address set, security settings enable, and support VLANS → Memorizes the # of addresses per switch port

• UnManaged: Plug/Play Switch, no configuration

Layer 2/3 Switches

Layer 2: Learns MAC address and sends traffic to the device

• Switches do NOT route traffic

Layer 3: Uses IP addresses, logical address of the device, routes traffic

Redundancy

• Has load balancing: multiple devices share a workload, increasing performance

• If one device fails, the other device takes over the workload

Backplane Speed

Total throughput a switch is capable of at any given time

Store-and-forward

• A switch will receive a data frame in its entirety, check for errors, and then forward the frame

Cut-through

A switch needs to know the frame header that has the destination MAC address and then it sends the frame

Hub

• Before switches, they were the central devices used to direct traffic in LANS → took signal & sent them out to all devices (no idea who owns each MAC address

• Good repeaters, boosts data signal

• Does not store MAC addresses & forward data to specific locations

Spanning Tree Protocol

• Loops can occur in switches

  • Physical: device plugged into itself by accident

  • Receives multiple copies of the same frame of data as it goes through a network

• Searches, find, and destroys redundant links → found by BPDUs, once redundant link is found it’s destroyed

Routers

• Route traffic between networks, can only transmit data as fast as the media connected to them

• Most routers may not get the top speeds as advertised by the device itself

Static Route

A route defined by an administrator, when traffic destined for a certain network needs to go through a certain router

Dynamic Route

• In Windows,. TCP/IP is the default dynamic routing protocol

• Routing tables form and update as routers enter and exit a network infrastructure

RIP

• Distance-vector routing protocol, uses hop counts to determine the best route for data packets (doesn’t take speed into consideration)

• Routing tables are updated through receiving updates from nearby routers as a topology changes

OOSPF

• A link-state protocol that uses multiple factors to determine the best route (hops and speed)

• Routing tables are updated through receiving updates from nearby routers as a topology changes

Routing Tables

• Uses RAM within a router for storage

  • If a table becomes too large, it can affect the performance

Network Segmentation

• Act of physically and/or logically breaking up a network into smaller networks

  • Each group should be isolated from others → physical networks are easily broken up into multiple VLANS to create multiple logical networks!

QoS

• Helps solve delay, dropped packets, errors, jitter (inconsistency in signals), and out-of-order devliery

Convergence

• Root bridge router learns the topology of the network → distributes the topology to the remaining routers (takes seconds)

  • Temporary performance slowdown can be noticed, after changes have taken place (normal traffic flow should resume once convergence is completed)

Twisted-Pair Cable

• Used for Ethernet networks

• Signals travel up to 100m or 328 ft + Speed: 10 Mbps-10 Gbps

• Uses RJ-45 connectors

UTP

• 4 twisted pairs of wire, avoids EMI + Inexpensive and easy to install

STP

• Runs through high areas of EMI, has extra shielding to avoid EMI

• More expensive than UTP, twisting is enough to counter the effects of EMI

• Subject to crosstalk → damaged cable

Fiber optic cable

• Used more for WAN connections but used for high-speed LAN connections (storage area networks)

• Carries signals up to 70 km + Speed: 100 Mbps-10 Gbps (fastest)

• Least susceptible to EMI b/c data is transmitted with photons

• Expensive + Bend radius not generous

Single-mode

• Transmit one ray of light over long distance

Multimode

• Carries multiple rays of light for 600m

Plenum Cable

• Fire-retardant insulation jacket + Used in plenum and air handling spaces

• Gives off less smoke than other jacket plastics

Susceptibility (Wired & Wireless Networks)

Wired

• Power cables, EMI. Fluorescent lighting

Wireless

• Heavy machinery

• Walls

• Anything that runs on 2.4 GHz (microwave ovens + cordless phones)

TCP

• Connection-oriented protocol

• Data is broken into segments and numbered

• Requires an acknowledgement of received data

UDP

• A connectionless protocol

• Data streams from source to destination with no segment numbering/acknowledgement of data received

• Used for audio and video streaming + less overhead (favorable for high bandwidth streams)

Subnetting

The act of splitting up physical networks into logical networks → each subnet is its own separate network

Teredo

Provides IPv6 connectivity to IPv4 hosts

ISATAP

Transmits IPv6 packets between dual-stack nodes on an IPv4 network

6 to 4

Allows a router with a public IPv4 address to be an IPv6 gateway for a set of LANS

HTTP vs HTTPS

• Data not encrypted - HTTP

• Data encrypted - HTTPS

FTP

• used with HTTP + HTTPS

• To upload and download files to and from a web server