OSI Model

Discuss the major influences of user requirements on network evolution

Identify at least 3 reasons why the industry uses a layered network model

Identify the functions of each layer of the OSI model

Define and explain 5 steps of data encapsulation

Build the semester 2 lab topology

User Influence

LANs interconnected to provide access to computers or file servers in other locations.

End-user needs for higher bandwidth on the LANs.

Relaying technologies for WAN service.

OSI Model Review

Identifying Layer Elements

Establishing Communication

Following the Data

The Network Layer adds source and destination logical addresses creating a Datagram (Packet).The Data Link Layer now puts the Packet into a Frame to allow connectivity to other Network devices.Finally the Frame has to be converted to a pattern of 1’s and 0’s for transmission through the media.

Data will be divided into segments by the Transport Layer in order to provide reliable communication between two computers.

Layers 1,2 and 3

Describe the topology and functionality of various LANs, especially Ethernet

Explain the use of a MAC address Explain what IP addressing is Differentiate between IP address classes Explain what subnet masking is and how

it is used

Ethernet—The first of the major LAN technologies, it runs the largest number of LANs.

Token Ring—From IBM, it followed Ethernet and is now widely used in a large number of IBM networks.

FDDI—Also using tokens, it is now a popular campus LAN.

Ethernet Topology

Note: E0 indicates that the port is 10 Mb, F0 or Fa0 indicates 100 Mb

Addressing other Hosts

Where is the MAC Address?

Finding someone’s MAC address - ARP

Introduction to TCP/IP Addresses

Unique addressing that allows communication between end stations.

Path choice is based on location.

Each location is represented by an address.

Making it easier to manage with subneting.

Layers 4,5,6 and 7

Discuss the function of the application, presentation, and session layers qualitatively

Discuss in detail the function and processes of the transport layer

Application Layer Supports the communicating

component of an application.

Presentation Layer Provides code

formatting and conversion. Code formatting is used to make sure that applications have meaningful information to process. If it is necessary, this layer can translate between different data formats.

Session Layer

The session layer establishes, manages, and terminates sessions between applications. Essentially, the session layer coordinates service requests and responses that occur when applications communicate between different hosts.

Transport Layer

Transport layer segments the several upper-layer applications onto the same Layer 4 data stream. These segmentations allow users to reassemble the same upper-layer applications at the destination.

The Layer 4 data stream is a logical connection between the endpoints of a network.

The Transport layer ensures the integrity and reliability of the data using a method of flow control. Flow control avoids the problem of a host at one side of the connection overflowing the buffers in the host at the other side.

Major Points

Ensure that segments delivered will be acknowledged back to the sender.

Provide for retransmission of any segments that are not acknowledged.

Put segments back into their correct sequence at the destination.

Provide congestion avoidance and control.

WANs

Describe the purpose of WANs

Describe the characteristics of WANs

Identify Major WAN components

WAN’s purpose

WAN is used to interconnect Local Area Networks (LAN’s) that are separated by a large geographical area.

A Wide Area Network (WAN) operates at the OSI Physical and Data link layers.

The WAN provides for the exchanging of data packets between Routers and the LAN’s that the routers support.

WAN’s characteristics

It uses the services of carriers such as Regional Bell Operating Companies (RBOCs), Sprint, and MCI.

WANs use serial connections of various types to access bandwidth over wide-area geographies

WAN connects devices separated by wide areas.

Wan technologies

WAN devices

Routers that offer many services including internetworking and WAN interface ports.

Switches that connect to WAN bandwidth for voice, data, and video communication.

Modems that interface voice-grade services; channel service units/digital service units (CSU/DSU) that interface T1/E1 services; Terminal Adapters/Network Termination 1 (TA/NT1) that interface Integrated Services Digital Network (ISDN) services.

Communication servers that concentrate dialin and dial-out user communication.

WAN data-link protocols describe how frames are carried between systems on a single data link. They include protocols designed to operate over dedicated point-to-point, multipoint, and multiaccess switched services such as Frame Relay.

WAN standards typically describe both physical layer and data link

layer requirements.