Presentation on theme: "OSI Model n Discuss the major influences of user requirements on network evolution n Identify at least 3 reasons why the industry uses a layered network."— Presentation transcript:
OSI Model n Discuss the major influences of user requirements on network evolution n Identify at least 3 reasons why the industry uses a layered network model n Identify the functions of each layer of the OSI model n Define and explain 5 steps of data encapsulation n 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
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 n Describe the topology and functionality of various LANs, especially Ethernet n Explain the use of a MAC address n Explain what IP addressing is n Differentiate between IP address classes n Explain what subnet masking is and how it is used
EthernetEthernet—The first of the major LAN technologies, it runs the largest number of LANs. Token RingToken Ring—From IBM, it followed Ethernet and is now widely used in a large number of IBM networks. FDDIFDDI—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 n Unique addressing that allows communication between end stations. n Path choice is based on location. n Each location is represented by an address.
Making it easier to manage with subneting.
Layers 4,5,6 and 7 n Discuss the function of the application, presentation, and session layers qualitatively n Discuss in detail the function and processes of the transport layer
Application Layer n Supports the communicating component of an application.
Presentation Layer n 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 n 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 n 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. n The Layer 4 data stream is a logical connection between the endpoints of a network. n 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 n Describe the purpose of WANs n Describe the characteristics of WANs n Identify Major WAN components
WAN’s purpose n WAN is used to interconnect Local Area Networks (LAN’s) that are separated by a large geographical area. n A Wide Area Network (WAN) operates at the OSI Physical and Data link layers. n The WAN provides for the exchanging of data packets between Routers and the LAN’s that the routers support.
WAN’s characteristics n It uses the services of carriers such as Regional Bell Operating Companies (RBOCs), Sprint, and MCI. n WANs use serial connections of various types to access bandwidth over wide-area geographies n WAN connects devices separated by wide areas.
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.
n 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. n WAN standards typically describe both physical layer and data link layer requirements.
Data Link Layer: WAN Protocols n High-Level Data Link Control (HDLC) - An ISO standard. HDLC might not be compatible between different vendors because of the way each vendor has chosen to implement it. HDLC supports both point- to-point and multipoint configurations. n Frame Relay - Uses high-quality digital facilities. By using a simplified framing with no error correction mechanisms, Frame Relay can send Layer2 information very rapidly, compared to these other WAN protocols. n Point-to-Point Protocol (PPP) - Described by RFC 1661, two standards developed by the IETF. PPP contains a protocol field to identify the network-layer protocol. n Integrated Services Digital Network (ISDN) - A set of digital services that transmits voice and data over existing phone lines. Back
Ethernet n Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps. Ethernet is similar to the IEEE series of standards. Thin Ethernet n 10Base2- Thin Ethernet Thick Ethernet n 10Base5- Thick Ethernet Fiber optics n 10BaseF- Fiber optics Twisted Pair n 10BaseT- Twisted Pair Back
FDDI n Fiber Distributed Data Interface. LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses a dual-ring architecture to provide redundancy. Back
Token Ring n Token-passing LAN developed and supported by IBM. Token Ring runs at 4 or 16 Mbps over a ring topology. Similar to IEEE n IEEE LAN protocol that specifies an implementation of the physical layer and MAC sublayer of the data link layer. IEEE uses token passing access at 4 or 16 Mbps over STP cabling and is similar to IBM Token Ring. Back