Basic Networking | Finals Long Quiz Reviewer

Dynamic Host Configuration Protocol (DHCP)

• It is a network management protocol used on Internet Protocol (IP) networks.

• It automatically assigns IP addresses and other communication parameters to devices connected to the network using a client–server architecture

• Every device on a TCP/IP-based network must have a unique

  unicast IP address to access the network and its resources.

• Without this, IP addresses for new computers or computers that are moved from one subnet to another must be configured manually; IP addresses for computers that are removed from the network must be manually reclaimed.

• Valid TCP/IP configuration parameters for all clients on the

  network.

• Valid IP addresses, maintained in a pool for assignment to clients, as well as excluded addresses.

• Reserved IP addresses associated with particular DHCP clients. This allows consistent assignment of a single IP address to a single DHCP client.

• The lease duration, or the length of time for which the IP address can be used before a lease renewal is required.

The DHCP server stores the configuration information in a database that includes:

• Client-Server Model

• Client Requests

• Server Response

• Dynamic IP Configuration

How DHCP Works:

Client-Server Model

Consists of a centrally installed network DHCP server and client instances on each device.

Client Requests

When a device connects to the network, it requests parameters (e.g., IP address) from the DHCP server.

Server Response

The DHCP server provides the requested parameters to the client.

Dynamic IP Configuration

Eliminates manual configuration of network devices.

Scopes

Determine which IP addresses are provided to clients.

DHCP Scope

A pool of IP addresses on a subnetwork that the DHCP server can lease to clients.

Lease Duration

The period the DHCP server holds a leased IP address for a client.

• Network ID

• Subnet Mask

• Router Option

Scope Properties

Network ID

Defines the range of IP addresses.

Subnet Mask

Specifies the subnet for the network.

Router Option

Allows DHCP clients to access remote networks.

Security Considerations

• DHCP can be secured to prevent unauthorized devices from obtaining IP addresses.

• Use DHCP snooping and port security to enhance security.

• Simplified IP Address Management

• Reduced Configuration Errors

• Improved Network Scalability

• Centralized Control

• Resource Optimization

• Simplified Troubleshooting

• Security Enchancements

Benefits of DHCP:

Simplified IP Address Management

DHCP automatically assigns and manages IP addresses, making it easier for network administrators to keep track of devices and their associated addresses, says a blog post on Medium.

Reduced Configuration Errors

By automating IP address assignment, DHCP minimizes the risk of manual errors like typos or conflicts, according to Learn Microsoft.

Improved Network Scalability

DHCP allows for easy addition or removal of devices without requiring changes to the network configuration, says a blog post on Park Place Technologies.

Centralized Control

DHCP provides a central point for managing IP address allocation, making it easier to implement changes and updates across the network.

Resource Optimization

DHCP allows for efficient use of IP addresses by automatically releasing them when devices disconnect from the network, according to an article on LinkedIn.

Simplified Troubleshooting

DHCP logs DHCP transactions, making it easier to troubleshoot network issues related to IP addresses.

Security Enhancements

DHCP servers can be configured to assign IP addresses only to authorized devices based on MAC address filtering, enhancing network security.

Physical Connection

• Before any network communications can occur, a physical connection to a local network must be established.

• This connection could be wired or wireless, depending on the setup of the network.

• This generally applies whether you are considering a corporate office or a home.

• A Network Interface Card (NIC) connects a device to the network.

• Some devices may have just one NIC, while others may have multiple NICs (Wired and/or Wireless, for example).

• Not all physical connections offer the same level of performance.

Physical Layer

• Transports bits across the network media

• Accepts a complete frame from the Data Link Layer and encodes it as a series of signals that are transmitted to the local media

• This is the last step in the encapsulation process.

• The next device in the path to the destination receives the bits and re-encapsulates the frame, then decides what to do with it.

TCP/IP standards

Are implemented in software and governed by the IETF.

Physical Layer Standards

Are implemented in hardware and are governed by many organizations including:

• ISO

• EIA/TIA

• ITU-T

• ANSI

• IEEE

• Physical Components

• Encoding

• Signaling

Physical Layer Standards Address Three (3) Functional Areas:

Physical Components

• Are the hardware devices, media, and other connectors that transmit the signals that represent the bits.

• Hardware components like NICs, interfaces and connectors, cable materials, and cable designs are all specified in standards associated with the physical layer.

Encoding

• It converts the stream of bits into a format recognizable by the next device in the network path.

• This ‘coding’ provides predictable patterns that can be recognized by the next device.

• Examples of encoding methods include:

  • Manchester;

  • 4B/5B, and

  • 8B/10B.

Signaling

• This method is how the bit values, “1” and “0” are represented on the physical medium.

• The method of signaling will vary based on the type of medium being used

Bandwidth

• It is the capacity at which a medium can carry data.

• Digital bandwidth measures the amount of data that can flow from one place to another in a given amount of time; how many bits can be transmitted in a second.

• Physical media properties, current technologies, and the laws of physics play a role in determining available bandwidth.

Latency

Amount of time, including delays, for data to travel from one given point to another

Throughtput

The measure of the transfer of bits across the media over a given period of time

Goodput

• The measure of usable data transferred over a given period of time

• Goodput = Throughput - traffic overhead

Cooper Cabling

• It is the most common type of cabling used in networks today.

• It is inexpensive, easy to install, and has low resistance to electrical current flow.

• Limitations:

  • Attenuation – the longer the electrical signals have to travel, the weaker they get.

  • The electrical signal is susceptible to interference from two sources, which can distort and corrupt the data signals (Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) and Crosstalk).

• Mitigation:

  • Strict adherence to cable length limits will mitigate attenuation.

  • Some kinds of copper cable mitigate EMI and RFI by using metallic shielding and grounding.

  • Some kinds of copper cable mitigate crosstalk by twisting opposing circuit pair wires together.

1. Unshielded Twisted-Pair (UTP) Cable

2. Shielded Twisted-Pair (STP) Cable

3. Coaxial Cable

Types of Copper Cabling:

Unshielded Twisted Pair (UTP)

• The most common networking media.

• Terminated with RJ-45 connectors

• Interconnects hosts with intermediary network devices.

• Key Characteristics:

  1. The outer jacket protects the copper wires from physical damage.

  2. Twisted pairs protect the signal from interference.

  3. Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair.

• Properties:

  • It has four pairs of color-coded copper wires

    twisted together and encased in a flexible plastic

    sheath.

  • No shielding is used.

  • UTP relies on the following properties to limit crosstalk:

    • Cancellation - Each wire in a pair of wires uses opposite polarity. One wire is negative, the other wire is positive. They are twisted together and the magnetic fields effectively cancel each other and outside EMI/RFI.

    • Variation in twists per foot in each wire - Each wire is twisted a different amount, which helps prevent crosstalk amongst the wires in the cable.

Shielded Twisted Pair (STP)

• Better noise protection than UTP

• More expensive than UTP

• Harder to install than UTP

• Terminated with RJ-45 connectors

• Interconnects hosts with intermediary network devices.

• Key Characteristics:

  1. The outer jacket protects the copper wires from physical damage

  2. Braided or foil shield provides EMI/RFI protection

  3. Foil shield for each pair of wires provides EMI/RFI protection

  4. Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair

Coaxial Cable

• There are different types of connectors used with coax

  cable.

• Commonly used in the following situations:

  • Wireless installations - attach antennas to wireless devices

  • Cable internet installations - customer premises wiring.

• Consists of the following:

  1. Outer cable jacket to prevent minor physical damage

  2. A woven copper braid, or metallic foil, acts as the second wire in the circuit and as a shield for the inner conductor.

  3. A layer of flexible plastic insulation

  4. A copper conductor is used to transmit the electronic signals.

Properties of Fiber-Optic Cabling

• Not as common as UTP because of the expense involved

• Ideal for some networking scenarios

• Transmits data over longer distances at higher bandwidth than any other networking media

• Less susceptible to attenuation, and completely immune to EMI/RFI

• Made of flexible, extremely thin strands of very pure glass

• Uses a laser or LED to encode bits as pulses of light

• The fiber-optic cable acts as a wave guide to transmit light between the two ends with minimal signal loss

• Single-Mode Fiber

• Multimode

Types of Fiber Media

Single-Mode Fiber

• Very small core

• Uses expensive lasers

• Long-distance application

Multimode

• Larger core

• Uses less expensive LEDs

• LEDs transmit at different angles

• Up to 10 Gbps over 550 meter

Dispersion

• Refers to the spreading out of a light pulse over time.

• Increased dispersion means increased loss of signal strength.

• MMF has greater dispersion than SMF, with a the maximum cable distance for MMF is 550 meters.

1. Enterprise Networks

2. Fiber-to-the-Home (FTTH)

3. Long-Haul Networks

4. Submarine Cable Networks

Fiber-optic cabling is now being used in Four (4) types of industry:

Enterprise Networks

Used for backbone cabling applications and interconnecting infrastructure devices

Fiber-to-the-Home

Used to provide always-on broadband services to homes and small businesses

Long Haul Networks

Used by service providers to connect countries and cities

Submarine Cable Networks

Used to provide reliable high-speed, high-capacity solutions capable of surviving in harsh undersea environments at up to transoceanic distances.

Wireless Media

• It carries electromagnetic signals representing binary digits using radio or microwave frequencies.

• This provides the greatest mobility option.

• Wireless connection numbers continue to increase.

• Some of the limitations:

  • Coverage area- Effective coverage can be significantly impacted by the physical characteristics of the deployment location.

  • Interference- Wireless is susceptible to interference and can be disrupted by many common devices.

  • Security- Wireless communication coverage requires no access to a physical strand of media, so anyone can gain access to the transmission.

  • Shared medium- WLANs operate in half-duplex, which means only one device can send or receive at a time. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user.

Wireless Standards

• The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers.

• In each of these standards, physical layer specifications dictate:

  • Data to radio signal encoding methods

  • Frequency and power of transmission

  • Signal reception and decoding requirements

  • Antenna design and construction

• Wi-Fi (IEEE 802.11)

• Bluetooth (IEEE 802.15)

• WiMAX (IEEE 802.16)

• Zigbee (IEEE 802.15.4)

Types of Wireless Standards:

Wi-Fi (IEEE 802.11)

Wireless LAN (WLAN) technology

Bluetooth (IEEE 802.15)

Wireless Personal Area network (WPAN) standard

WiMAX (IEEE 802.16)

Uses a point-to-multipoint topology to provide broadband wireless access

Zigbee (IEEE 802.15.4)

• Low data-rate

• Low power-consumption communications

• Primarily for Internet of Things (IoT) applications

Wireless LAN

• In general, a Wireless LAN (WLAN) requires the following devices:

  • Wireless Access Point (AP)

  • Wireless NIC Adapters

• There are a number of WLAN standards.

  • When purchasing WLAN equipment, ensure compatibility, and interoperability.

• Network Administrators must develop and apply stringent security policies and processes to protect WLANs from unauthorized access and damage.

Wireless Access Point (AP)

Concentrate wireless signals from users and connect to the existing copper-based network infrastructure

Wireless NIC Adapters

Provide wireless communications capability to network hosts

Data Link Layer

• It is responsible for communications between end-device network interface cards.

• It allows upper layer protocols to access the physical layer media and encapsulates Layer 3 packets (IPv4 and IPv6) into Layer 2 Frames.

• It also performs error detection and rejects corrupts frames.

Providing Access to Media

• Packets exchanged between nodes may experience numerous data link layers and media transitions.

• At each hop along the path, a router performs four basic Layer 2 functions:

  • Accepts a frame from the network medium.

  • De-encapsulates the frame to expose the encapsulated packet.

  • Re-encapsulates the packet into a new frame.

  • Forwards the new frame on the medium of the next network segment.

• Institute for Electrical and Electronic Engineers (IEEE).

• International Telecommunications Union (ITU).

• International Organizations for Standardization (ISO).

• American National Standards Institute (ANSI)

Data link layer protocols are defined by engineering organizations:

Topology of a Network

It is the arrangement and relationship of the network devices and the interconnections between them.

• Physical topology

• Logical topology

There are two types of topologies used when describing networks:

Physical topology

It shows physical connections and how devices are interconnected.

Logical topology

It identifies the virtual connections between devices using device interfaces and IP addressing schemes.

1. Point-to-point

2. Hub and spoke

3. Mesh

There are three (3) common physical WAN topologies:

Point-to-Point WAN Topology

• The simplest and most common WAN topology.

• Consists of a permanent link between two endpoints.

• Physical point-to-point topologies directly connect two nodes.

• The nodes may not share the media with other hosts.

• Because all frames on the media can only travel to or from the two nodes, Point-to-Point WAN protocols can be very simple.

Hub and spoke

It’s similar to a star topology where a central site interconnects branch sites through point-to-point links.

Mesh

It provides high availability but requires every end system to be connected to every other end system.

LAN Topologies

• End devices on LANs are typically interconnected using a star or extended star topology.

1. Bus

2. Ring

Early Ethernet and Legacy Token Ring technologies provide two (2) additional topologies:

Bus

All end systems chained together and terminated on each end.

Ring

Each end system is connected to its respective neighbors to form a ring.

Star and extended star topologies

Topologies that are easy to install, very scalable and easy to troubleshoot.

Half-duplex communication

• Only allows one device to send or receive at a time on a shared medium.

• Used on WLANs and legacy bus topologies with Ethernet hubs.

Full-duplex communication

• Allows both devices to simultaneously transmit and receive on a shared medium.

• Ethernet switches operate in full-duplex mode.

1. Contention-based access

2. Controlled access

Access Control Methods:

Contention-based access

• All nodes operating in half-duplex, competing for use of the medium.

• Examples are:

  • Carrier sense multiple access with collision detection (CSMA/CD) as used on legacy bus-topology Ethernet.

  • Carrier sense multiple access with collision avoidance (CSMA/CA) as used on Wireless LANs.

Controlled access

• Deterministic access where each node has its own time on the medium.

• Used on legacy networks such as Token Ring and ARCNET

Contention-Based Access – CSMA/CD

• CSMA/CD

  • Used by legacy Ethernet LANs.

  • Operates in half-duplex mode where only one device sends or receives at a time.

    Uses a collision detection process to govern when a device can send and what happens if multiple devices send at the same time.

• CSMA/CD collision detection process:

  • Devices transmitting simultaneously will result in a signal collision on the shared media.

  • Devices detect the collision.

  • Devices wait a random period of time and retransmit data.

Contention-Based Access – CSMA/CA

• CSMA/CA

  • Used by IEEE 802.11 WLANs.

  • Operates in half-duplex mode where only one device sends or receives at a time.

  • Uses a collision avoidance process to govern when a device can send and what happens if multiple devices send at the same time.

• CSMA/CA collision avoidance process:

  • When transmitting, devices also include the time duration needed for the transmission.

  • Other devices on the shared medium receive the time duration information and know how long the medium will be unavailable.

Data Link Frame

• Data is encapsulated by the data link layer with a header and a trailer to form a frame.

• The fields of the header and trailer vary according to data link layer protocol.

• The amount of control information carried with in the frame varies according to access control information and logical topology.

1. Header

2. Data

3. Trailer

A data link frame has three (3) parts:

Layer 2 Addresses

• Also referred to as a physical address.

• Contained in the frame header.

• Used only for local delivery of a frame on the link.

• Updated by each device that forwards the frame.

LAN and WAN Frames

• The logical topology and physical media determine the data link

  protocol used:

  • Ethernet

  • 802.11 Wireless

  • Point-to-Point (PTP)

  • High-Level Data Link Control (HDLC)

  • Frame-Relay

• Each protocol performs media access control for specified logical topologies.

VLAN

• Stands for Virtual Local Area Network.

• It is a technology used in networking to segment a physical network into multiple isolated broadcast domains logically.

• Allows you to group devices together even if they are not physically connected to the same switch, as if they were in the same room or office.

• Benefits:

  1. Security - Isolate sensitive data (e.g., HR or Finance).

  2. Performance - Reduces broadcast traffic by limiting broadcast domains.

  3. Flexibility - Users can be grouped logically, not physically.

  4. Manageability - Easier to manage and troubleshoot large networks.

Trunking

• It is used to carry multiple VLANs across a single link between switches or between a switch and a router.

• It allows devices on different VLANs (across switches) to communicate as if they're on the same VLAN.

IPv6 (Internet Protocol version 6)

• The newest version of Internet Protocol, designed to replace IPv4

• Designed by the Internet Engineering Task Force (IETF)

• Has a 128-bit address length

• Has no subnet mask

IPv6 Address Compression

• Consists of eight groups of four hexadecimal digits separated by a ‘:’

• Leading zeros can be omitted (trailing zeros cannot)

• A single instance of continuous zeros can be replaced with a double colon (::)

• There are supposed to be 8 hextets of 4 hexadecimal characters each.

Network Portion

2001:0db8:0000:0000:a111:b222:c333:abcd/64

• The highlighted part of the IPv6 address is the _______

Host Portion

2001:0db8:0000:0000:a111:b222:c333:abcd/64

• The highlighted part of the IPv6 address is the _______

Global Unicast

• It is a publicly routable address like the IPv4 public IPs.

• The prefix to identify these address is 2000::/3

  • This means the first 3 bits identify a global unicast address.

  • It will start with either a 2 or a 3.

Unique Local

• Its like an IPv4 private IPs

• Not globally routable

• The prefix to identify these address is FC00::/7

  • Using the first seven bits, a unique local address will always start with an F followed by either a C or D.

Link Local

• Quick automatic private IP addresses that are not routable over a network.

• Designed to communicate only within a single area of network.

Multicast

• Are addresses that are sent to a group of computers or devices listening for that particular multicast.

• IPv4, also same as broadcast addresses, these were sent to all computers within a network, these have now been scrapped with IPv6

Anycast

• IPv6 allows us to assign the same IP address to multiple devices.

• The data is then sent to the closest device with that address.

• No specific IP range for anycast.

• Used the same range to unicast.