OSI Layers

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No.	Name	Protocol(s)	Remarks
7	Application Layer	DNS, HTTP, HTTPS, IMAP, POP3, SMTP, SSH	Concerned with headers, cookies, content, etc.
6	Presentation Layer		Concerned with encryption.
5	Session Layer		Attach session tag.
4	Transport Layer	ALPN, OCSP, SNI, SSL, TCP, TLS, UDP	Attach ports and sequence nos. Each individual part is called a segment.
3	Network Layer	AH, BGP, EIGRP, ESP, ICMP, IGRP, IKE, IP, IPSEC, ISAKMP, IS-IS, OSPF, RIP	Attach IP add. Each individual part is called a packet.
2	Data Link Layer	ARP, DHCP	Attach MAC add. Each individual part is called a frame.
1	Physical Layer		Data transfer in 1s and 0s.

NOTE: Corresponding to the OSI model, there exists a TCP/IP model as well.

Resources

• The OSI Model
• What the Session, Presentation and Application Layers actually do
• The Internet that Wasn’t (OSI)
• Encapsulation explained and why Ping (part of ICMP) doesn’t work at layer three and even then ICMP is considered as a layer three protocol.
• Protocols