8. Protocols
Protocols are likened to rulebooks that define how data is transmitted, and receives accross network. They are essential for maintaining order and standardization in network communication.
TCP and UDP:- Data delivery methods
TCP (Transmission control protocol):- Ensure reliable data delivery by confirming data arrival and order, like sending a registered letter.
UDP (User Datagram Protocol):- Focuses on speed, sending data without confirmation, akin to droped a post card in the email.
| OSI Layer | Protocols |
|---|---|
| Layer 7: Application | HTTP, HTTPS, FTP, SMTP, DNS |
| Layer 6: Presentation | SSL/TLS, JPEG, MPEG, GIF |
| Layer 5: Session | NetBIOS, RPC, PPTP |
| Layer 4: Transport | TCP, UDP, SCTP |
| Layer 3: Network | IP, ICMP, IGMP, ARP |
| Layer 2: Data Link | Ethernet, PPP, Frame Relay |
| Layer 1: Physical | Ethernet (cabling), DSL, USB |
| TCP/IP Layer | Protocols |
|---|---|
| Layer 4: Application | HTTP, HTTPS, FTP, SMTP, DNS |
| Layer 3: Transport | TCP, UDP, SCTP |
| Layer 2: Internet | IP (IPv4, IPv6), ICMP, ARP |
| Layer 1: Network Interface | Ethernet, Wi-Fi (802.11), PPP |
| Introduction to protocol:- Protocols are like the secret rules for procedures for data transmission between electronic devices, ensuring smooth communication the traffic flaws of internet highways. |
HTTP and HTTPS:- Web browsing essentials
HTTP(Hyper text transfer protocol:- Foundation for web data exchange, governing how files (text, images, videos are transmitted online.)
HTTPS( https secure):- A secure version of HTTP, encrypting communication between browsers and websites, crucial for secure data transmission like credit card into.
FTP:- Efficient file transfer
FTP (File Transfer Protocol:- A workhorse protocol for moving large files or group of files between.
SMTP (simple mail transfer protocol):- Sends emails from send to recipent's email server.
IMAP (Internet Message access protocol):- Retreives email from the email server, allowing access from multiple devices.
POP(Post office protocol):- Retrieves email from the email server but typically download them to a single device, removing them from the server.
- SYN: The client sends a SYN (synchronize) packet to the server to initiate a connection.
- SYN-ACK: The server responds with a SYN-ACK (synchronize-acknowledge) packet to acknowledge the receipt of the SYN.
- ACK: The client sends an ACK (acknowledge) packet back to the server, completing the handshake and establishing the connection.
Error detection is done by ARQ
ARQ (Automatic repeat request) : When a packet is lost receiver don't send a ACK to sender and sender get to know something want wrong and send the packet again.
TCP connections are terminated gracefully using a four-way handshake:
- FIN: One side (e.g., client) sends a FIN (finish) packet to terminate the connection.
- ACK: The other side acknowledges the FIN with an ACK.
- FIN: The second side then sends its own FIN to terminate the connection.
- ACK: The first side acknowledges this FIN, and the connection is fully closed.
The TCP header is typically between 20 byte to 60 bytes
| Field | Size (Bits) | Description |
|---|---|---|
| Source Port | 16 | The port number of the sender |
| Destination Port | 16 | The port number of the receiver |
| Sequence Number | 32 | The sequence number of the first byte of data |
| Acknowledgment Number | 32 | The next sequence number that the sender expects |
| Data Offset | 4 | The size of the TCP header in 32-bit words |
| Reserved | 3 | Reserved for future use |
| Flags | 9 | Control flags (e.g., URG, ACK, PSH, RST, SYN, FIN) |
| Window Size | 16 | Size of the sender’s receive window (flow control) |
| Checksum | 16 | Used for error-checking of the header and data |
| Urgent Pointer | 16 | Indicates if there is urgent data |
| Options (if any) | Variable | Additional options (e.g., Maximum Segment Size) |
| Padding | Variable | Padding to ensure the header is a multiple of 32 bits |
The IP header (for IPv4) is typically 20 bytes but can also be longer with options. The structure is as follows:
| Field | Size (Bits) | Description |
|---|---|---|
| Version | 4 | IP version (e.g., 4 for IPv4) |
| IHL (Internet Header Length) | 4 | Length of the IP header in 32-bit words |
| Type of Service (ToS) | 8 | Defines the quality of service parameters |
| Total Length | 16 | Total length of the IP packet (header + data) |
| Identification | 16 | Unique identifier for the fragment |
| Flags | 3 | Control flags for fragmentation |
| Fragment Offset | 13 | Position of the fragment in the original packet |
| Time to Live (TTL) | 8 | Limits the packet's lifetime |
| Protocol | 8 | Indicates the transport layer protocol (e.g., TCP=6, UDP=17) |
| Header Checksum | 16 | Used for error-checking of the header |
| Source IP Address | 32 | IP address of the sender |
| Destination IP Address | 32 | IP address of the receiver |
| Options (if any) | Variable | Additional options (if any) |
| Padding | Variable | Padding to ensure the header is a multiple of 32 bits |
UDP is suitable for applications such as: UDP is ideal for real-time and low-latency applications where some packet loss is acceptable, such as ✓ video streaming ✓ online gaming ✓ VoIP (Voice over IP) ✓ DNS queries ✓ IoT device communication.
DHCP Server (Dynamic Host Configuration Protocol) : Routers can assign IP addresses to devices on the network automatically, which simplifies network management.