CSE 220 Midterm 2

ARP (Address Resolution Protocol)

A network protocol used to map IP addresses to physical MAC addresses in a local area network.

Domain Name Service - DNS

A system that translates human-readable domain names into IP addresses, allowing browsers to load Internet resources.

• operates at application layer

DHCP (Dynamic Host Configuration Protocol)

protocolthat automatically assigns IP addresses to devices on a network

Network Address Translation - NAT

maps private IP addresses to a public IP address and vice versa, allowing multiple devices to share a single public IP

Source NAT (SNAT)

• Changes the source IP address in a packet (usually your device’s IP) to a public IP.

• Used when you go out to the internet.

• Example: Your private IP 192.168.1.5 becomes 72.100.40.1 as it leaves your home network.

Destination NAT (DNAT)

• Changes the destination IP address of incoming packets.

• Used for port forwarding — to send traffic from the internet to a specific device inside a private network.

• Example: A request to 72.100.40.1 on port 80 is forwarded to 192.168.1.10 inside your network.

encapsulation

• Definition: process of wrapping data with protocol-specific headers as it moves down the OSI model (from Application to Physical). Each layer adds its own information to help transmit the data.

• Purpose: Help data move across network layers

• Example: When sending a packet over TCP/IP, data is encapsulated in a TCP segment, then in an IP packet, and finally in an Ethernet frame.

ethernet

A family of networking technologies used in local area networks (LANs) that defines wiring and signaling standards for physical connections and how data is formatted and transmitted at Layer 2 (Data Link Layer).

TCP (Transmission Control Protocol)

network protocol that allows for reliable, in order, transport of data

1. splits data into packets with each packet having sequence # for reassembly

2. sends them over the internet

3. waits for ACKs that each packet arrives

4. if packet missing, it resends packet

UPD

A connectionless protocol used to send data quickly without guaranteeing delivery. Used for streaming, gaming, and VoIP.

IPv4

32 bit addressing system used to identify devices on a network

• ex: 192.16.4.99

• security is optional

IPv6

128 bit successor of IPv4, designed to accommodate more devices with a vastly larger address space

• supports encryption and other security features to prevent address spoofing

ex: 2001:db8:3333:4444:5555:6666:7777:8888

HTTP

An Application-layer protocol used for transferring web pages and resources between web servers and clients.

MAC address

A unique hardware address assigned to a network interface card (NIC) used to identify devices on a local network. Works at the Data Link layer.

IP address

logical address used to identify a device on network and route data between networks

VPN

creates secure, encrypted connection/tunnel over a public network, often used for privacy or remote access

• takes original IP packet and wraps it in another IP packet with different source and destination to hide real IP address from the public

• private IP packet is encapsulated inside public one

tunneling

• Definition: A technique that encapsulates a protocol within another protocol so it can traverse an incompatible network.

• Purpose: Send private data through public places

• Example: VPNs use tunneling (e.g., GRE, IPSec, L2TP) to wrap private network traffic within public network protocols.

checksum

value used to verify integrity of data during transmission. if it doesnt match on receiving end, an error is assumed

1. sum up every 8-bit (byte) chunk of data

2. take modulo 16

3. add that sum to packet to make sure data isnt corrupted

• ex: byte 1 = 01000011 = 67

• byte 2 = 00010001 = 17

• 67 + 17 = 84

• 84 % 16 = 4 ← add to data

port

identifier for the source or destination program

common numbers = 80 for HTTP, 443 for HTTPS, 22 for SSH

address

A binary number used to define the network and host portions of an IP address. It always starts with a series of 1s followed by 0s.

sequence number

a value used in TCP to keep track of the order of packets in a data transmission, ensuring proper reassembly and delivery.

window size

in TCP, the amount of data in bytes that can be sent before requiring an acknowledgement - used for flow control

subnet masks in binary…

always follows the form of a series of 1s followed by 0s

PAT (Port Address Translation)

• A type of NAT that uses ports to let multiple private devices share one public IP.

• It’s what your home router uses so all your devices can go online at once.