COSC 85 - Reviewer

Network Protocols

Standardized rules and procedures that govern how devices communicate and exchange data over a network

Network Protocols

They break down complex tasks into smaller functions, ensuring smooth, reliable, and secure communication for everything from web browsing to email and file transfers

Enable Communication
Define Data Handling
Manage Flow

What Network Protocols Do?

Enable Communication

This allow diverse devices (PCs, servers, phones) to talk, regardless of internal differences.

Define Data Handling

This specify data formatting, addressing, packaging, and error checking.

Manage Flow

This act like traffic signals to regulate data movement, preventing errors and ensuring delivery.

HTTP
HTTP/3
HTTPS
WebSocket
TCP
UDP
SMTP
FTP

Network Protocols

HTTP (Hypertext Transfer Protocol)

This is a protocol for fetching resources such as HTML documents. It is the foundation of any data exchange on the Web and it is a client-server protocol.

HTTP/3

This is the next major

revision of the HTTP. It runs on QUIC, a new transport protocol designed for mobile-heavy internet usage. It relies on UDP instead of TCP, which enables faster web page responsiveness.

HTTPS (HyperText Transfer Protocol Secure)

This extends HTTP and uses encryption for secure communications.

WebSocket

is a protocol that provides full-duplex communications over TCP. Clients establish this to receive real- time updates from the back-end services.

TCP (Transmission Control Protocol)

This is designed to send packets across the internet and ensure the successful delivery of data and messages over networks. Many application-layer protocols build on top of this.

UDP (User Datagram Protocol)

This sends packets directly to a target computer, without establishing a connection first. This is commonly used in time-sensitive communications where occasionally dropping packets is better than waiting. Voice and video traffic are often sent using this protocol.

SMTP (Simple Mail Transfer Protocol)

This is a standard protocol to transfer electronic mail from one user to another.

FTP (File Transfer Protocol)

This is used to transfer computer files between client and server. It has separate connections for the control channel and data channel.

Menu Bar

This part contains standard file, edit, options, view, tools, and help menus, providing access to basic commands like open, save, and print.

Main Tool Bar

This part offers shortcut icons for frequently used menu commands, including new, open, save, print, activity wizard, copy, paste, undo, and redo.

Logical/Physical Workspace Tabs

These tabs allow you to toggle between the Logical and Physical work areas.

Common Tools Bar

This part Offers access to primary workspace tools, including Select, Inspect, Delete, Resize Shape, Place Note, Drawing Palette, Add Simple PDU (packet icon), and Add Complex PDU.

Workspace

This is the area where topologies are created and simulations are displayed.

Realtime/Simulation tabs

These tabs are used to toggle between the real and simulation modes. Buttons are also provided to control the time, and to capture the packets.

Network component box

This component contains all of the network and end devices available with Packet Tracer, and is further divided into two areas

Network component box (Device-type selection box)

This area contains device categories

Network component box (Device-specific selection box)

When a device category is selected, this selection box displays the different device models within that category

User-created packet box

In this part, users can create highly-customized packets to test their topology from this area, and the results are displayed as a list.

Router > - User EXEC Mode
Router # - Privileged EXEC Mode
Router(Config) # - Global Configuration Mode
Router(Config-if) # - Interface Mode
Router(Config Router) # - Routing Engine Mode
Router(Config-Line) # - Line Mode

User Levels and Modes in Cisco Packet Tracer

Router > - User EXEC Mode

This mode is primarily for read-only monitoring. Users can check basic hardware and software status using limited show commands. You can also perform basic connectivity tests like ping and traceroute.

Router # - Privileged EXEC Mode

Often called "Enable Mode," this level grants full administrative visibility. It is the "hub" for advanced troubleshooting and management.

Router(Config) # - Global Configuration Mode

This is where you implement system-wide changes that affect the entire device

Router(Config-if) # - Interface Mode

Used to configure individual physical or virtual ports. Here you assign IP addresses, set link speeds, or enable/disable ports with no shutdown.

Router(Config Router) # - Routing Engine Mode

Used for setting up routing protocols. Inside this mode, you define which networks a protocol like OSPF or RIP should advertise to other devices.

Router(Config-Line) # - Line Mode

Used to secure access points. You enter this mode to set passwords for the console (physical access) or vty (remote Telnet/SSH access) lines

Start Up Configuration
Running Configuration
Configuration Register

Other Cisco Packet Tracer Necessity

Running Configuration

This is also known as the "current configuration" or "active configuration" is the configuration that is currently active and operational on the network device. Changes made here take effect immediately.

Startup Configuration

Also known as the "saved configuration" or "boot configuration" is the configuration that is saved on the device's non-volatile memory. It represents the configuration that will be loaded and applied to the device when it boots up or is restarted.

Configuration Register

This is a 16-bit software value stored in a Cisco device's non-volatile RAM (NVRAM) that acts as a set of boot instructions.

Configuration Register (0x2142) - Password Recovery Mode

This setting is specifically used when you need to bypass existing security settings.

Configuration Register (0x2102) – Default Mode

This is the factory-default setting for most Cisco routers. The router boots normally by loading the Cisco IOS software from Flash memory and the startup-config from NVRAM. The router loads the IOS from Flash but completely ignores the startup-config in NVRAM.

Mitigation of Data Breaches
Maintaining Brand Trust and Reputation
Prevention of Credential Stuffing
Protection Against Future Threats
Regulatory and Legal Compliance
Defending Against Insider Threats

Why Password Encryption is Important?

Slow Network
Weak Wi-Fi Signal
Physical Connectivity Issues
Excessive CPU Usage
Slow DNS Lookups
Duplicate and Static IP Addresses
Exhausted IP Address
Virtual LAN and VPN problems

Common Network Issues

Slow Network

High bandwidth usage from activities like 4K streaming or large file downloads saturates the connection, often exacerbated by outdated hardware that cannot handle modern internet speeds.

Weak Wi-Fi Signal

Signal strength degrades due to physical distance from the router or interference from thick walls, metal objects, and other electronic devices operating on the same frequency.

Physical Connectivity Issues

Sudden outages or intermittent connections are frequently caused by loose connectors, damaged Ethernet cables, or faulty hardware ports.

Excessive CPU Usage

Routers and switches may become sluggish or unresponsive when their processors are overwhelmed by high traffic volumes, malware, or complex encryption tasks.

Slow DNS Lookups

When an ISP’s DNS server is slow or non-responsive, the time it takes to translate a website name into an IP address increases, leading to long loading delays.

Duplicate and Static IP Addresses

Connectivity fails for one or more devices when two pieces of hardware are assigned the same IP address, causing a conflict on the network.

Exhausted IP Address

This occurs when the DHCP server has no more available addresses to hand out, preventing new devices from joining the network.

Virtual LAN and VPN problems

These issues typically involve incorrect VLAN tagging on network switches or authentication and encryption failures within a VPN tunnel.