Lets take a look at OSI 7 layer model and comparison to TCP/IP model.
Table 1 – OSI Model Summary
|7. Application||Interfacing between communications software and any applications that need to communicate outside the computer. It also define proccess for user authentication.|| |
HTTP, Telnet, DNS,DHCP, SNMP, FTP, TFTP, SMTP, POP3, NTP
|6. Presentation||Data representation (define and negotiate data formats),encryption and decryption.|| |
SSL, Shells and Redirectors, MIME
|5. Session||Interhost communication. How to start, control, and end conversations (called session). An application can be notified if some of series of messages are completed. Allow presentation layer to have view of an incoming stream of data.|| |
NetBIOS, Sockets, RPC
|4. Transport||End-to-end connections and reliability,error recovery, and Flow control|| |
TCP and UDP, SPX, NetBEUI/NBF
|3. Network||Three main feature : logical addressing, routing (forwarding), and path determination. IP Address, routing protocols, and routing table belong to this layer|| |
IPv4, IPv6, IP NAT, IPsec, ICMP, IPX, Routing protocols
|2. Data Link||Defines how data is formatted for transmission and how access to the network is controlled. This layer has been divided by the IEEE 802 standards committee into two sublayers: media access control (MAC) and logical link control (LLC).|| |
IEEE 802.2 LLC, Ethernet Family; Token Ring; FDDI, IEEE 802.11 (WLAN, Wi-Fi),ATM, SLIP and PPP
|1. Physical||Media, signal and binary transmission. Refer to standard of physical characterstics of transmission medium such as connector, pins, use of pins, electrical currents, encoding, light modulation, and other rules about physical medium|| |
Physical layers technologies (RS-232, Full duplex, RJ45, V.35,T1, E1, 10BASE-T, 100BASE-TX, POTS, SONET, SDH, DSL, 802.11a/b/g/n, etc
Table 2 will show you comparison of OSI model and TCP/IP model, also encapsulation at each layers.
Table 2 - OSI vs TCP/IP Model, and encapsulation at each layers
|7. Application||4. Application||Data||Data|
|4. Transport||3. Transport||Segments||TCP/UDP Header||Data|
|3. Network||2. Internet||Packets||IP Header||TCP/UDP Header||Data|
|2. Data Link||1. Network Access||Frames||MAC Header||IP Header||TCP/UDP Header||Data||CRC|
|1. Physical||Bits||Transmit into Physical Media (Bit Format)|
Talking about encapsulation, bits transmitted from sender over physical media, at the receiving device will de-encapsulated from bits into frames, and so on untill arrived at Application layer.
Please find Sample CCNA exam (OSI and TCP/IP Model) to check if you already understand this material.