Physical Layer OF THE OSI Model

Physical Layer OF THE OSI Model

OSI Model


·         Layer 7 = Application: file, print, message, database, and application services
Layer 6 = Presentation: data encryption , compression and translation services
Layer 5 = Session: Dialog control
Layer 4 = Transport: End to End connection
Layer 3 = Network: Routing
Layer 2 = Data Link: Framing
Layer 1 = Physical: Physical Topology


Physical Layer OF THE OSI Model


·         Layer 1: Provides the means for transmitting data packets over a physical medium. Specifies the electrical and mechanical characteristic of the network. Receives fully formatted data packets from the Data Link layer. ie Hubs


Technologies that Function at the Physical Layer


·         Ethernet
2. Fast Ethernet
3. Asynchronous Transfer Mode (ATM)
4. token ring


Data Link Layer OF THE OSI Model


·         Layer 2: Responsible for error free transfer of data packets on a network and for grouping data packets into frames and attaching the address of the receiving node to each frame - thus forming the data packet. Also adds error correction and detection codes to frames. ie switches, PPP and SLIP


Two Sub-layers of the Data Link Layer


·         MAC
2. LLC


In a contention based network the MAC sub-layer is responsible for WHAT?


·         For the Carrier Sense to detect collision. In an Ethernet network it controls elements of addressing such as error notification ,the frame delivery sequence and flow control.


In a Token Passing network the MAC sub-layer is responsible for WHAT?


·         For the token.


TCP/IP Model vs the OSI model


·         APPLICATION - Layer 7-5 (application, presentation and session)
TRANSPORT - Layer 4 (transport)
INTERNET - Layer 3 (network)
NETWORK INTERFACE - Layer 2-1 (data link and physical


Network Design configurations that are affected by the Physical layer of the OSI model


-       Bandwidth of the transmission medium
- Type of transmission medium ie copper
- Switching technologies
- Mode of transmission (wired or wireless)
- Analog or digital transmission
- modulation


MAC Sub-layer of the Data Link Layer


·         Media Access Control: Defines how packets are placed on the media.


LLC Sub-layer of the Data Link Layer


·         Logical Link Control:
- ID's Network Layer protocols and encapsulating those protocols so that multiple upper layer protocols can share the same media.
- Controls the Physical Layer device and also performs error control.
-Checks the CRC of the frame and either ACK or NACK the data.
-Controls data flow to maintain the bandwidth of the network medium.
-Tells the Data Link Layer how to handle the frame it receives.


Network Layer OF THE OSI Model


·         Layer 3 - Responsible for addressing and routing the data packets from a source to a destination through a network. Ensures delivery of packets across a network. Responsible for controlling congestion on the network by taking proper routing decisions. ie routers and some switches


Transport Layer OF THE OSI Model


·         Layer 4 - Accepts data from upper layers and breaks it into smaller units, aka segments. Passes the segments to the lower layers and ensures that all segments arrive correctly at the receiving end. Adds a sequence number to reconstruct original sequence of segments. Responsible for error correction and sending acknowledgments at the network level.


What are the protocols that operate at the Transport Layer?


·         TCP (transmission control protocol)
UDP (user datagram protocol)
PPTP (Point to Point Tunneling Protocol)
L2TP (Layer 2 Tunneling Protocol)


Network Layer OF THE OSI Model defines protocols for interconnecting two or more similar networks such as these....


·         IP
ARP (address resolution protocol)
ICMP (internet control message protocol)
RIP (routing information protocol)
OSPF (open shortest path first)
BGP (boarder gateway protocol)
IGMP (internet group management protocol)


Network and Transport Layer Protocols contain protocol families. What are the 3 categories?


·         1.Reliability
2. Connection
3. Routing



Reliability Protocols


·         Provides a method of ensuring reliable data transfer. ie.. A header or trailer might contain a Checksum value or request that you need to acknowledge received data by sending an acknowledgement message back to the sender. TCP (transmission control protocol)


Connection Protocols


·         Establish and maintain a connectionless or connection-oriented service for the upper layers. In a connection-oriented service, the sending and receiving nodes maintain constant communication to mediate the transfer of data. Sequencing, flow control and reliability are monitored at both ends. In a connectionless service, the message is packaged, delivered and sent. the message is transferred only if communication exits between the two nodes. UDP (user datagram protocol)


Routing Protocols


·         Provides a method of ensuring data transfer to the correct destination. In an unswitched network, routing is virtually unnecessary because the nodes are directly connected. In a switched network, the routing protocol determines the path a packet will take to reach its destination. this function is particularly important and complex in a packet-switched network, because there can be many possible paths to a destination and many intermediary devices such as routers along the path. Routing protocols determine the strategies used to transmit data through the network. RIP, OSPF, PPTP


Checksum Value


·         Lets the receiver test the integrity of received data.


Session Layer OF THE OSI Model


·         Layer 5 - Establishes connections between network devices and applications, maintains the connection, and then terminates or reestablishes it when required. Controls how, when and for how long a device can transmit or receive data. Specifies procedures for synchronizing data transfer between two devices with different data transmission rates.


Sockets and session establishment in TCP function at this OSI layer


·         Session Layer


Gateways operate at this OSI layer. Ports are referred here also


·         Transport Layer


Presentation Layer OF THE OSI Model


·         Layer 6 - Responsible for encoding data into a standard network-compatible format, which enable devices with different representation techniques to communicate with each other. Adds services such as data compression and encryption.


What are the technologies and protocols that operate at the Presentation Layer?

MME (mesh made easy)

SSL (secure socket layer)
TLS (transport layer security)
GIF (graphics interchange format)
JPEG (joint photographic experts group)
TIFF (tagged imaged file format)


Application Layer OF THE OSI Model


·         Layer 7 - Offers services and utilities that enable application access to the network and its resources.


What are the technologies and protocols that operate at the Application layer?


·         HTTP
FTP (file transfer protocol)
NFS (network file system)
NTP (network time protocol)
SMTP (simple mail transfer protocol)
SNMP (simple network management transfer protocol)



What are the 7 Application, Presentation and Session layers protocol families (aka Application layer of the TCP/IP model)


·         Terminal-Emulation protocols
2. File access and file transfer protocols
3. Email protocols
4. Remote-action and multiple-session protocols
5. Network management protocols
6. Task to task protocols
7. Codeset and data structure protocols


Terminal-Emulation protocols


·         Allow the user access to a text terminal and all its applications. Enable computers to act as standard terminals so that they can access hosts.


File access and file transfer protocols


·         File access protocols: enable nodes to access files on the network. provide a common means to access network files.
File transfer protocols: Enable copying of files between network storage and other storage, such as a computers local disk drive.


Email protocols


·         Provide for email delivery and handling of messages


Remote-action and multiple-session protocols


·         Remote-action protocols: Determine whether processes should be performed remotely on a client node or directly by a server. Required for setting up a client-server relationship.
Multiple-session protocols: Enable multiple network links to be established.


Network management protocols


·         Provide tools for setting up and maintaining the network


Task to task protocols


·         Enable software processes to communicate over the network.


Codeset and data structure protocols


·         Define the representation of data. Translate data for nodes that use different coding schemes.


The OSI Data Communication Process


·         Sender goes through the model from 7 to 1. the receiver goes from 1 to 7.


Application Layer of the TCP/IP network model


·         Provides definition of protocols for file, mail and hypertext transfer. Handles the encoding of data and controlling of the sessions. Defines socket services and other utilities over TCP/IP.


Transport Layer of the TCP/IP network model


·         Provides connection establishment and communication services. Defines protocols for end to end transfer of data, along with error and flow controls.


Internet Layer of the TCP/IP network model


·         Provides addressing and routing services. Controls congestion on the network. Involves transferring data from a source to destination network when multiple networks are connected together.


Network Interface Layer of the TCP/IP network model


·         Provides services to send and receive data packets on the network. Defines protocols for moving data frames between adjacent nodes and for accessing the medium by the devices. Defines the protocols for encoding and transmitting data over the network media.


OSI was developed to standardize networking. TRUE/FALSE


·         True


TCP/IP model was specifically developed to execute Internet related tasks. TRUE/FALSE


·         TRUE


The OSI model was invented after protocols


·         FALSE



TCP/IP protocols are the standards around which the Internet was developed. The functionality allotted at each layer is perfectly optimized.


·         TRUE


In the TCP/IP model each layer uses different terminologies for a unit of information. What are they?


·         Application - Data
Transport - Segment
Internet - Datagram or packets
Network Interface - Frames



Data Encapsulation


·         Process of adding delivery information to the actual data transmitted on each layer. Takes place in the transmission end as data is passed down the layers. At the receiving end, the reverse process of removing the added information is done as data passes to the next higher layer in a process called de-encapsulation. The added information is called a header if it is before the data or a trailer if it is added after the data.



Protocol Binding look


·         Assigning a protocol to a NIC. This creates a path for the flow of data. In windows you can specify the binding order in which to bind protocols to a NIC.




·         The quality of data segments, measured in bytes, that the transmitting machine is allowed to send without receiving an acknowledgement.



You will find Bridges and switches on what layer?


·         Data link layer


What layer is responsible for converting data into signals?


·         Physical layer


What are two purposes for segmentation with a bridge?


·         To create more Collision domains and to add more bandwidth for users


Which layer 1 devices can be used to enlarge the area covered by a single Lan segment?


·         Hub and repeater



Service Firms vs. Manufacturing Firms


·         Manufacturing firms - produce tangible, physical goods, such as cars or food products

Service firms - produce nonphysical outputs in the form of services, such as medical and transportation services

>Economy is dominated by creation and sale of services



Value Chain Management


·         Value - the performance characteristics, features, and attributes, and any other aspects of goods and services for which customers are willing to give up resources for (usually money)

>Value is provided to customers through transforming raw materials and other resources into some product or service that end users need or desire when, where, and how they want it

Value chain management - the process of managing the sequence of activities and information along the entire value chain
>Externally oriented and focuses on both incoming materials and outgoing products and services
>Effectiveness-oriented and aims to create the highest value for customers




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