# Cisco Networking/CCENT/Networking Models

This lesson covers the TCP/IP and OSI networking models and encapsulation concepts.

## Objectives and Skills

Objectives and skills for the TCP/IP and OSI networking models portion of Cisco CCENT certification include:
* Describe the purpose and basic operation of the protocols in the OSI and TCP/IP models
* Recognize the purpose and functions of various network devices such as routers, switches, bridges and hubs
* Identify common applications and their impact on the network
* Predict the data flow between two hosts across a network

## Readings

* Wikipedia: OSI model
* Wikipedia: Internet protocol suite
* Wikipedia: Encapsulation (networking)
* Cisco: Internetworking Basics

## Multimedia

* YouTube: The OSI Model - CompTIA Network+ N10-005 - 1.1
* YouTube: The OSI Model in the Real World - CompTIA Network+ N10-005: 1.2
* YouTube: The TCP/IP Model - CompTIA Network+ N10-005: 1.1
* YouTube: Networking Protocols - CompTIA Network+ N10-005: 1.6
* YouTube: Network Layers - OSI, TCP/IP Models - Part 1
* YouTube: Network Layers - OSI, TCP/IP Models - Part 2
* YouTube: Network Layers - OSI, TCP/IP Models - Part 3

## Activities

* Review OSI Components. Describe the purpose and basic operation of the layers in the OSI and TCP/IP models.
* Draw your own personal reference chart comparing the Internet protocol suite four-layer model to the OSI seven-layer model.
* Use Wireshark to capture network traffic on your school, work, or home network. Identify the protocols in use on the network at each layer of the OSI and TCP/IP models.
* Use Wireshark to capture network traffic on your school, work, or home network. Identify the protocol data unit headers and layer interaction as data is encapsulated from segment to packet to frame for transmission as bits.

## Lesson Summary

* The Open Systems Interconnection model (OSI Model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard for the underlying internal structure and technology.
* The OSI model is a seven-layer model containing Physical, Data Link, Network, Transport, Session, Presentation, and Application layers.
* The OSI model layers are numbered from the bottom up:
** 7 - Application
** 6 - Presentation
** 5 - Session
** 4 - Transport
** 3 - Network
** 2 - Data Link
** 1 - Physical
* The OSI model is maintained by the International Organization for Standardization (ISO).
* The OSI Physical layer transmits and receives raw bit streams over a physical medium.
* The OSI Data Link layer reliably transmits data frames between two nodes connected by a physical layer.
* The OSI Network layer manages packet addressing, routing, and traffic control.
* The OSI Transport layer ensures reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing.
* The OSI Session layer manages information exchange between two nodes, including authentication and authorization.
* The OSI Presentation layer manages translation (formatting) of data, including character encoding, data compression, and encryption/decryption.
* The OSI Application layer provides APIs (application programming interfaces) to support resource sharing, remote file access, directory services, virtual terminals, etc.
* The Internet protocol suite is the set of communications protocols used for the Internet and similar networks.
* The Internet protocol suite is a four-layer model containing Link, Internet, Transport, and Application layers.
* The Internet protocol suite is maintained by the Internet Engineering Task Force (IETF).
* The Link layer contains communication technologies for a local network.
* The Internet layer connects local networks, thus establishing internetworking.
* The Transport layer handles host-to-host communication.
* The Application layer contains all protocols for specific data communications services on a process-to-process level.
* The Internet protocol suite protocols are deliberately not as rigidly designed into strict layers as in the OSI model.
* The Internet Link layer includes the OSI Data Link and Physical layers, as well as parts of OSI's Network layer.
* The Internet internetworking layer (Internet layer) is a subset of the OSI Network layer.
* The Internet Transport layer includes the graceful close function of the OSI Session layer as well as the OSI Transport layer.
* The Internet Application layer includes the OSI Application layer, Presentation layer, and most of the Session layer.
* Internet Link layer protocols include Ethernet, Wi-Fi, and PPP.
* Internet internetworking layer (Internet layer) protocols include IP, ICMP and IGMP.
* Internet Transport layer protocols include TCP and UDP.
* Internet Application layer protocols include HTTP and SMTP,

## Key Terms
### adjacent-layer interaction

    Each lower layer provides a service to the layer or layers above it.

### bit

    The OSI Physical layer protocol data unit.

### deencapsulation

    Each layer interprets and removes header (and sometimes trailer) control information before passing a PDU to the layer above.

### encapsulation

    Each lower layer adds header (and sometimes trailer) control information to the PDU received from the layer above.

### frame

    The OSI Data Link layer protocol data unit.

### networking model

    A conceptual model that describes and represents network function, exemplified by the OSI model and the Internet Protocol Suite.

### packet

    The OSI Network layer protocol data unit.

### protocol data unit (PDU)

    Information that is delivered as a unit among peer entities of a network and that may contain control information, such as address information, or user data.

### same-layer interaction

    Each layer communicates with its corresponding layer on the receiving node.

### segment

    The OSI Transport layer protocol data unit.

## Review Questions

* The Open Systems Interconnection model (OSI Model) is _____. The Open Systems Interconnection model (OSI Model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard for the underlying internal structure and technology.
* The OSI model is a _____-layer model containing _____ layers. The OSI model is a seven-layer model containing Physical, Data Link, Network, Transport, Session, Presentation, and Application layers.
* The OSI model layers are numbered from the bottom up as: The OSI model layers are numbered from the bottom up as 7 - Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 - Data Link 1 - Physical
* The OSI model is maintained by _____. The OSI model is maintained by the International Organization for Standardization (ISO).
* The OSI Physical layer _____. The OSI Physical layer transmits and receives raw bit streams over a physical medium.
* The OSI Data Link layer _____. The OSI Data Link layer reliably transmits data frames between two nodes connected by a physical layer.
* The OSI Network layer _____. The OSI Network layer manages packet addressing, routing, and traffic control.
* The OSI Transport layer _____. The OSI Transport layer ensures reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing.
* The OSI Session layer _____. The OSI Session layer manages information exchange between two nodes, including authentication and authorization.
* The OSI Presentation layer _____. The OSI Presentation layer manages translation (formatting) of data, including character encoding, data compression, and encryption/decryption.
* The OSI Application layer _____. The OSI Application layer provides APIs (application programming interfaces) to support resource sharing, remote file access, directory services, virtual terminals, etc.
* The Internet protocol suite is _____. The Internet protocol suite is the set of communications protocols used for the Internet and similar networks.
* The Internet protocol suite is a _____-layer model containing _____ layers. The Internet protocol suite is a four-layer model containing Link, Internet, Transport, and Application layers.
* The Internet protocol suite is maintained by _____. The Internet protocol suite is maintained by the Internet Engineering Task Force (IETF).
* The Link layer _____. The Link layer contains communication technologies for a local network.
* The Internet layer _____. The Internet layer connects local networks, thus establishing internetworking.
* The Transport layer _____. The Transport layer handles host-to-host communication.
* The Application layer _____. The Application layer contains all protocols for specific data communications services on a process-to-process level.
* The Internet protocol suite protocols are _____ as in the OSI model. The Internet protocol suite protocols are deliberately not as rigidly designed into strict layers as in the OSI model.
* The Internet Link layer includes the OSI _____. The Internet Link layer includes the OSI Data Link and Physical layers, as well as parts of OSI's Network layer.
* The Internet internetworking layer (Internet layer) is a subset of the OSI _____ layer. The Internet internetworking layer (Internet layer) is a subset of the OSI Network layer.
* The Internet Transport layer includes the graceful close function of the OSI _____ layer as well as the OSI _____ layer. The Internet Transport layer includes the graceful close function of the OSI Session layer as well as the OSI Transport layer.
* The Internet Application layer includes the OSI _____. The Internet Application layer includes the OSI Application layer, Presentation layer, and most of the Session layer.
* Internet Link layer protocols include _____. Internet Link layer protocols include Ethernet, Wi-Fi, and PPP.
* Internet internetworking layer (Internet layer) protocols include _____. Internet internetworking layer (Internet layer) protocols include IP, ICMP and IGMP.
* Internet Transport layer protocols include _____. Internet Transport layer protocols include TCP and UDP.
* Internet Application layer protocols include _____. Internet Application layer protocols include HTTP and SMTP.

## Assessments

* Flashcards: Quizlet: CCENT - Networking Models
* Quiz: Quizlet: CCENT - Networking Models

## See Also

* Internet Protocol Analysis/Introduction