1.1 Compare the layers of the OSI and TCP/IP models
What Layer of the OSI model does a AP operate
Access point (AP) operate at the Data link (Layer 2)
Three Characters at the MAC Layer at the Data link Layer
Physical addressing: A common example of a Layer 2 address is a MAC address,which is a 48-bit address assigned to a device's network interface card (NIC). Logical topology: Layer 2 devices view a network as a logical topology. Examples of a logical topology include bus and ring topologies Method of transmitting on the media: With several devices connected to a network, there needs to be some strategy for determining when a device is allowed to transmit on the media. Otherwise, multiple devices might transmit at the same time, and interfere with one another's transmissions
Service addressing at the Transport Layer
Protocols such as TCP/IP support many network services. The transport layer ensures that data is passed to the right service at the upper layers of the OSI model.
Service advertisement at Layer 7
Service advertisement: Some applications' services (for example, some networked printers) periodically send out advertisements, making the availability of their service known to other devices on the network. Other services, however, register themselves and their services with a centralized directory (for example, Microsoft Active Directory), which can be queried by other network devices seeking such services.
Network Interface Layer of TCP/IP stack
The TCP/IP stack's network interface layer encompasses the technologies addressed by Layers 1 and 2 (physical and data link layers) of the OSI model.
Application Layer Of The TCP/IP model
The biggest difference between the TCP/IP stack and the OSI model is found at the TCP/IP stack's application layer. This layer addresses concepts described by Layers 5, 6, and 7 (the session, presentation, and application layers) of the OSI model. Application layer protocols in the TCP/IP stack are identifiable by unique port numbers .
What other Name does the TCP/IP model go by
This model is known as the DoD model, as it was developed by the department of defence or the TCP/IP stack .
Segmentation at the Transport Layer
To traverse the network, blocks of data need to be broken into packets of a manageable size for the lower layers to handle. This process, called segmentation, is the responsibility of the transport layer.
Layers Of The OSI model
Layer 7 - Application Layer 6 - Presentation Layer 5 - Session Layer 4 - Transport Layer 3 - Network Layer 2 - Data link Layer 1 - Physical
Error checking at the Data Link Layer
A mathematical algorithm is performed on the data to create a cyclic redundancy check (CRC). If both the sender and receiver calculate the same CRC value for the same chunk of data, the receiver can conclude that the data was not corrupted during transmission.
What happens at the Physical Layer
At the physical layer, binary expressions (that is, a series of 1s and 0s) represent data. A binary expression is made up of bits, where a bit is a single 1 or a single 0. How bits are represented on the medium Wiring standards for connectors and jacks Physical topology Synchronizing bits Bandwidth usage Multiplexing strategy
Characteristics of the Logical Link Control (LLC) sublayer of the Data Link Layer
Connection services: When a device on a network receives a message from another device on the network, that recipient device can provide feedback to the sender in the form of an acknowledgment message. Flow control: Limits the amount of data a sender can send at one time; this prevents the receiver from being overwhelmed with too much information. Error control: Allows the recipient of data to let the sender know if the expected data frame was not received or if it was received, but is corrupted. Synchronizing transmissions: Senders and receivers of data frames need to coordinate when a data frame is being transmitted and should be received. Examples Isochronous, Asynchronous and Synchronous.
What Layer of the OSI model does a Bridge operate
Data link (Layer 2)
What Layer of the OSI model does a NIC operate
Data link (Layer 2)
What Layer of the OSI model does a Switch operate
Data link (Layer 2) or network (Layer 3) for a multi-function switch
Application services at layer 7
Examples of the application services residing at the application layer include file sharing and e-mail.
Example other than TCP/UDP protocol at layer4
Internet Control Message Protocol (ICMP) is another transport layer protocol you are likely to encounter. ICMP is used by utilities such as ping and traceroute
What Layer of the OSI model does a Router operate
Network (Layer 3)
What are the layers of TCP/IP model
Network Interface Layer ( aka Network Access or Link layer) Internet Layer Transport Layer Application Layer
What does OSI abbreviation stand for?
Open Systems Interconnect
What Layer of the OSI model does a Hub operate
Physical (Layer 1)
Internet layer of TCP/IP model
The Internet layer of the TCP/IP stack maps to Layer 3 (the network layer) of the OSI model. Although multiple routed protocols (for example, IP, IPX, and AppleTalk) reside at the OSI model's network layer, the Internet layer of the TCP/IP stack focuses on IP as the protocol to be routed through a network
What happens at the Data Link Layer ?
The data link layer is concerned with packaging data into frames and transmitting those frames on the network, performing error detection/correction, uniquely identifying network devices with an address, and handling flow control. These processes are collectively referred to as data link control (DLC). The term frame describes the logical grouping of data at the data link layer. The data link layer has two distinct sublayers: Media Access Control (MAC) layer: The MAC address is defined at this layer. The MAC address is the physical or hardware address burned into each network interface card (NIC). The MAC sublayer also controls access to network media. The MAC layer specification is included in the IEEE 802.1 standard. Logical Link Control (LLC) layer: The LLC layer is responsible for the error and flow-control mechanisms of the data link layer. The LLC layer is specified in the IEEE 802.2 standard.
Application Layer ( Layer 7)
The function of the application layer is to take requests and data from the users and pass them to the lower layers of the OSI model. Incoming information is passed to the application layer, which then displays the information to the users. Some of the most basic application-layer services include file and print capabilities. Two basic services include • Application services and Service advertisement
Presentation Layer (Layer 6)
The presentation layer's basic function is to convert the data intended for or received from the application layer into another format. Such conversion is necessary because of how data is formatted so that it can be transported across the network. Applications cannot necessarily read this conversion. Some common data formats handled by the presentation layer include the following: Graphics files: JPEG, TIFF, GIF, and so on are graphics file formats that require the data to be formatted in a certain way. Text and data: The presentation layer can translate data into different formats, such as American Standard Code for Information Interchange (ASCII) and Extended Binary Coded Decimal Interchange Code (EBCDIC). Sound/video: MPEG, MP3, and MIDI files all have their own data formats to and from which data must be converted. Another important function of the presentation layer is encryption, which is the scrambling of data so that it can't be read by anyone other than the intended recipient. Given the basic role of the presentation layer—that of data-format translator—it is the obvious place for encryption and decryption to take place.
Layer 3: The Network Layer
The primary responsibility of the network layer is routing—providing mechanisms by which data can be passed from one network system to another. The network layer does not specify how the data is passed, but rather provides the mechanisms to do so.Functionality at the network layer is provided through routing protocols, which are software components. Protocols at the network layer are also responsible for route selection, which refers to determining the best path for the data to take throughout the network. In contrast to the data link layer, which uses MAC addresses to communicate on the LAN, network layer protocols use software configured addresses and special routing protocols to communicate on the network. The term packet describes the logical grouping of data at the network layer.
Session Layer (Layer 5)
The session layer is responsible for managing and controlling the synchronization of data between applications on two devices. It does this by establishing, maintaining, and breaking sessions. Whereas the transport layer is responsible for setting up and maintaining the connection between the two nodes, the session layer performs the same function on behalf of the application.
Transport Layer of The TCP/IP model
The transport layer of the TCP/IP stack maps to Layer 4 (the transport layer) of the OSI model. The two primary protocols found at the TCP/IP stack's transport layer are TCP and UDP.
Transport Layer (Layer 4)
The transport layer, acts as a dividing line between the upper layers and lower layers of the OSI model. Specifically, messages are taken from upper layers (Layers 5-7) and are encapsulated into segments for transmission to the lower layers (Layers 1-3). Similarly, data streams coming from lower layers are decapsulated and sent to Layer 5 (the session layer), or some other upper layer, depending on the protocol. The Transport Layer is associated with TCP/UDP Windowing Buffering The basic function of the transport layer is to provide mechanisms to transport data between network devices. Primarily it does this in three ways: Error checking, Service addressing, Segmentation
Two common transport layer protocols
Transmission Control Protocol (TCP): A connection-oriented transport protocol. Connection-oriented transport protocols provide reliable transport, in that if a segment is dropped, the sender can detect that drop and retransmit that dropped segment. Specifically, a receiver acknowledges segments that it receives. Based on those acknowledgments, a sender can determine which segments were successfully received and which segments need to be transmitted again. User Datagram Protocol (UDP): A connectionless transport protocol. Connectionless transport protocols provide unreliable transport, in that if a segment is dropped, the sender is unaware of the drop, and no retransmission occurs.
Two common flow control approaches at Layer 4
Windowing: Data is sent in groups of segments that require only one acknowledgment. The size of the window (that is, how many segments fit into one acknowledgment) is defined when the session between the two devices is established. As you can imagine, the need to have only one acknowledgment for every, say, five segments can greatly reduce overhead. Buffering: With buffering, a device (for example, a router) allocates a chunk of memory (sometimes called a buffer or a queue) to store segments if bandwidth is not currently available to transmit those segments. A queue has a finite capacity, however, and can overflow (that is, drop segments) in the event of sustained network congestion. When buffering flow control is used, data is temporarily stored and waits for the destination device to become available. Buffering can cause a problem if the sending device transmits data much faster than the receiving device can manage.
Example of real world Physical Layer
Wiring standard:ethernet 568A/B standard Physical Topology: Bus, Ring, Star, Mesh Telephone network modems Ethernet physical layer Including 10BASE-T, 10BASE2, 10BASE5, 100BASE-TX, 100BASE-FX, 100BASE-T, 1000BASE-T, 1000BASE-SX and other varieties Varieties of 802.11 Wi-Fi physical layers DSL ISDN T1 and other T-carrier links, and E1 and other E-carrier links SONET/SDH Optical Transport Network (OTN)
