Confused by the OSI Model or trying to remember which port goes with which protocol? We’ve got you covered! Check out this super-handy 𝐎𝐒𝐈 𝐌𝐨𝐝𝐞𝐥, 𝐏𝐨𝐫𝐭𝐬 & 𝐏𝐫𝐨𝐭𝐨𝐜𝐨𝐥𝐬 𝐂𝐡𝐞𝐚𝐭 𝐒𝐡𝐞𝐞𝐭. ➡️ It breaks down: ✅ All 7 OSI layers (from Physical to Application) ✅ Common protocols like HTTP, FTP, DNS, and SSH ✅ Default port numbers and protocol numbers ✅ The difference between port number vs protocol number

1. OSI
MODEL, PORTS, AND PROTOCOLS
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CHEAT SHEET

2. Layer Function
Common
Protocols /
Technologies
Transmit raw bits over
physical medium
Ethernet (physical), USB,
DSL, Wi-Fi (PHY)
Ethernet (MAC), ARP,
PPP, VLAN, Wi-Fi (MAC)
Node-to-node data
transfer, MAC addresses
Logical addressing &
routing
IP (IPv4/IPv6), ICMP, OSPF,
BGP, IGMP
TCP, UDP, SCTP
End-to-end data transfer,
flow control
Manage sessions and
connections
NetBIOS, PPTP, RPC
Data translation,
encryption, compression
SSL/TLS, JPEG, MPEG, ASCII
Layer 1: Physical
Layer 2: Data Link
Layer 3: Network
Layer 4: Transport
Layer 5: Session
Layer 6: Presentation
Layer 7: Application
Network services to
applications
HTTP, HTTPS, FTP, SMTP,
DNS, SSH, SNMP
Note: Some protocols span multiple layers of the OSI model.
Example: DNS operates at both the Application and Transport layers
(uses TCP/UDP port 53).
• 0–1023: Well-known ports (assigned by IANA)
• 1024–49151: Registered ports
• 49152–65535: Dynamic/private ports
Well-Known Port Ranges
OSI Model Layers & Key Protocols

3. Common Protocols and
Default Port Numbers
Protocol Port(s) TCP / UDP Description
Web traffic
(non-secure)
Secure web traffic
(SSL/TLS)
File transfer control
File transfer data
Secure remote login
Remote terminal
access
Email sending
Domain Name
System
Email retrieval
Advanced email
retrieval
Network
management
Directory services
Windows file
sharing
Remote desktop
Network time
synchronization
VoIP signaling
System logging
MySQL database
server
Microsoft SQL
Server
Simple file transfer
HTTP
HTTPS
FTP (Control)
FTP (Data)
SSH
Telnet
SMTP
DNS
POP3
IMAP
SNMP
LDAP
SMB
RDP
NTP
SIP
Syslog
MySQL
MSSQL
TFTP
DHCP
80
443
21
20
22
23
25
53
110
143
161
389
445
3389
123
5060
514
3306
1433
69
67 (server),
68 (client)
Dynamic IP
addressing
TCP
TCP
TCP
TCP
TCP
TCP
TCP
TCP/UDP
TCP
TCP
UDP
TCP/UDP
TCP
UDP
TCP/UDP
UDP
TCP
TCP
UDP
UDP
TCP

4. Protocol Protocol Number Description
1
Internet Control Message
Protocol
Transmission Control
Protocol
6
17 User Datagram Protocol
Open Shortest Path First
(Routing)
89
2
Internet Group Management
Protocol
ICMP
TCP
UDP
OSPF
IGMP
Protocol Numbers (Used in IP
Header to Identify Protocol)

5. Difference Between Port
Number and Protocol Number
Feature Port Number Protocol Number
A numeric identifier used
by Transport Layer
(TCP/UDP) to specify a
particular
application/service on a
host.
Direct data to the
correct
application/process on
a device (e.g., HTTP
runs on port 80).
Layer 4 (Transport Layer)
16-bit number, ranges
from 0 to 65535
Used in TCP and UDP
headers to
differentiate multiple
services on the same
IP address.
• HTTP: port 80 TCP
• DNS: port 53
UDP/TCP
A numeric identifier
assigned to protocols at
the Network Layer (IP) to
indicate which protocol is
encapsulated in the IP
packet payload.
Identify the protocol type
inside an IP packet (e.g.,
TCP, UDP, ICMP).
Layer 3 (Network Layer)
8-bit number, ranges
from 0 to 255
Used in the IP header’s
"Protocol" field to specify
which protocol to hand data
to at the receiving device.
• TCP protocol number: 6
• UDP protocol number: 17
• ICMP protocol number: 1
Definition
OSI Layer
Range/Format
Purpose
Where Used
Examples
Quick Analogy
Protocol Number = The type of mail (e.g., letter, postcard, package)
that tells the post office how to handle the mail.
Port Number = The apartment number inside the building where
the mail should be delivered.