Saeed Darvish Pazoki – MCSE, CCNA Abstracted From: Cisco Press – ICND 1 – Chapter 2 Sybex – CCNA Study Guide The TCP/IP and OSI Networking Models 1

The TCP/IP Protocol Architecture OSI Model 2

The TCP/IP Protocol Architecture 3

History of Networking Model Simplifies networking by dividing it into less complex components. Enables programmers to specialize in a particular layer Provides modularity which allows upgrades to a specific layer to remain separate from the other layers. Encourage interoperability by promoting balance between different networking models. Allows for standardized interfaces to be produced by vendors. 4

5 Layer 1 - Physical

OSI Model Media Type: 1. “Speed” 2. “Distance” 3. Signaling 4. Connectors 5. Pinout Signaling Electricity - (Bounded Media) Radio Frequency (RF) - (Un-bounded Media) Optics – (Bounded and Un-bounded Media) 6

OSI Model Physical Layer Protocols and Standards: Ethernet Variants: 10BASE-T 100BASE-T 1000BASE-T 100BASE-FX 1000BASE-LX 1000BASE-SX PDH (E-Carrier/T-Carrier) ISDN xDSL RS-232 SDH SONET 7

OSI Model Physical Layer Protocols and Standards: 8

OSI Model Physical Layer Protocols and Standards: 9

10 Layer 2 – Data-Link

OSI Model Layer-2 Functions: Physical Addressing (MAC) Access to the Media (CSMA/CD) Error-Detection (FCS/CRC) Framing 11

OSI Model Layer-2 Standards and Protocols: Ethernet STP (Spanning-Tree Protocol) VTP (VLAN Trunking Protocol) HDLC PPP SLIP FDDI Token-Ring Frame-Relay PPTP L2TP 12

13 Layer 3 – Network

OSI Model Layer-3 Functions: Logical Addressing Routing (Path Selection) Layer-3 Standards and Protocols: IP IPX ICMP IPSec 14

OSI Model 15

16 Layer 4 – Transport

OSI Model Layer-4 Functions: Multiplexing Error recovery Flow control Connection establishment / Termination Ordering Data 17

OSI Model Transport Layer The TCP/IP transport layer consists of two main protocol options: Transmission Control Protocol (TCP) User Datagram Protocol (UDP) TCP/IP needs a mechanism to guarantee delivery of data across a network. Because many application layer protocols probably want a way to guarantee delivery of data across a network, TCP provides an error-recovery feature to the application protocols by using acknowledgments. 18

OSI Model Transport Layer The higher-layer protocol (HTTP) needs to do something it cannot do (error recovery). So, the higher layer asks for the next lower-layer protocol (TCP) to perform the service, and the next lower layer performs the service. The lower layer provides a service to the layer above it. 19

OSI Model Transport Layer 20

OSI Model Transport Layer 21

22 Layer 5,6,7 – Session, Presentation and Application

The TCP/IP Protocol Architecture Application Layer TCP/IP application layer protocols provide services to the application software running on a computer. The application layer does not define the application itself, but rather it defines services that applications need. 23

OSI Model Architecture Layer-7 Standards and Protocols: DHCP DNS FTP TFTP HTTP SMTP SNMP Telnet SSH NTP SIP Syslog 24

The TCP/IP Protocol Architecture 25

Data Encapsulation 26

The TCP/IP Protocol Architecture Data Encapsulation Each TCP/IP layer adds its own header (and sometimes trailer) to the data supplied by the higher layer. The term encapsulation refers to the process of putting headers and trailers around some data. 27

The TCP/IP Protocol Architecture 28

The TCP/IP Protocol Architecture Data Encapsulation The steps are summarized in the following list: Create and encapsulate the application data with any required application layer headers. For example, the HTTP OK message can be returned in an HTTP header, followed by part of the contents of a web page. Encapsulate the data supplied by the application layer inside a transport layer header. For end-user applications, a TCP or UDP header is typically used. Encapsulate the data supplied by the transport layer inside an internet layer (IP) header. IP is the only protocol available in the TCP/IP network model. Encapsulate the data supplied by the internet layer inside a network access layer header and trailer. This is the only layer that uses both a header and a trailer. Transmit the bits. The physical layer encodes a signal onto the medium to transmit the frame. 29

The TCP/IP Protocol Architecture Data Encapsulation Like TCP/IP, OSI defines processes by which a higher layer asks for services from the next lower layer. To provide the services, the lower layer encapsulates the higher layer’s data behind a header. The TCP/IP model uses terms such as segment, packet, and frame to refer to various layers and their respective encapsulated data. OSI uses a more generic term: protocol data unit, or PDU. A PDU represents the bits that include the headers and trailers for that layer, as well as the encapsulated data. OSI defines encapsulation similarly to how TCP/IP defines it. All layers except the lowest layer define a header, with the data from the next higher layer being encapsulated behind the header. The data link layer defines both a header and a trailer and places the Layer 3 PDU between the header and trailer. 30

The TCP/IP Protocol Architecture Data Encapsulation 31

The TCP/IP Protocol Architecture OSI Model 32