Chapter 2 Introducing the Host-To-Host Communications Model

What is a PDU called at the Link layer?

frames

Layers 1 to 4, the lower layers, are concerned with what?

how content is transferred over the network.

Transport layer summarized

Supports communication between end devise across a diverse network

Link layer

controls the hardware devices and media that make up the network

What is a PDU called at the internet layer

packet

Layers 5 to 7, or upper layers, are concerned with What?

user interaction and the information that is communicated, its presentation and how the communication proceeds.

TCP/IP Model Layers

1. Link/Network Interface 2. Internet 3. Transport 4. Application

host-to-host communications model, important concepts:

1.Identification of layers and functions of Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite, its layers, and functions 2.Comparison to Open Systems Interconnection (OSI) reference model because it is an alternative to the TCP/IP protocol suite 3.How information is transmitted from the sender to the receiver across the network 4.Encapsulation and de-encapsulation processes on network and end devices

What are the 7 layers of the OSI model?

7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical

Transport Layer

Along with the Internet layer, this layer is the core of the TCP/IP architecture. It is placed between so called "data mover" protocols of the Link and Internet layers and software-oriented protocols of the Application layer. There are two main protocols at this layer, TCP and User Datagram Protocol (UDP). These protocols serve many application layer protocols. Transport services "prepare" application data for transfer over the network, follow on the transfer process, and make sure that data from different applications' is not mixed. To distinguish between the applications, the transport layer identifies each application with its own addressing. This addressing is valid locally, within one host, unlike addressing at the Internet layer, which is valid globally.

what is a PDU called at the application layer

DATA

An example of the TCP/IP link layer protocol is

Ethernet

Internet layer summarized

Provides logical addressing and determines the best pathing through the network.

what is a PDU called at the Transport Layer

Segment

TCP/IP Model

The TCP/IP model defines and describes requirements for the implementation of host systems. These include standard protocols that these systems should use. It does not specify how to implement the protocol functions, but rather provides guidance for vendors, implementors and users of what should be provided within the system.

Layer 7

The application layer is the OSI layer that is closest to the user. It provides services to user applications that want to use the network. Services include e-mail, file transfer, and terminal emulation. An example of a user application is the web browser. It does not reside at the application layer, but is using protocols that operate at the application layer. Operating systems also use the application layer when performing tasks triggered by actions that typically do not involve communication over the network. Examples of such actions are opening a remotely located file with a text editor or importing a remotely located file into spreadsheet. The application layer differs from other layers in that it does not provide services to any other OSI layer.

Layer 2

The data link layer defines how data is formatted for transmission and how access to physical media is controlled. This layer typically includes error detection and correction to ensure reliable data delivery. The data link layer involves network interface controller to network interface controller (NIC-to-NIC) communication within the same network. This layer uses a physical address to identify hosts on the local network

Application layer /TCP/IP Stack

The functions of this layer mainly deal with user interaction. It supports user applications by providing protocols and services that let you actually use the network. It also supports network application programming interfaces (APIs), that allow programs to access the network services, regardless of the operating system that they are running on. This layer accommodates protocols such as Hypertext Transfer Protocol (HTTP), Secure HTTP (HTTPS), Domain Name System (DNS), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Secure Shell (SSH), and many more. These protocols facilitate applications for web browsing, file transfer, names to IP addresses resolution, sending of e-mails, remote access to devices, and many other functions that network users perform.

Layer 3:

The network layer provides connectivity and path selection beyond the local segment, all the way from the source to the final destination. The network layer uses logical addressing to manage connectivity. In networking, the logical address is used to identify the sender and the recipient. The postal system is another common system that uses addressing to identify the sender and the recipient. Postal addresses follow the format that includes name, street name and number, city, state, and country. Network logical addresses have a different format than postal addresses; they are determined by the network layer rules. Logical addressing ensures that a host has a unique address or that it can be uniquely identified in terms of network communication.

Layer 1

The physical layer defines electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between devices. This layer deals with electromagnetic representation of bits of data and their transmission. Physical layer specifications define line encoding, voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other attributes. This layer is the only layer implemented solely in hardware.

Layer 6

The presentation layer ensures that data sent by the application layer of one system is "readable" by the application layer of another system. It achieves that by translating data into a standard format before transmission and converting that format into a format known to the receiving application layer. It also provides special data processing that must be done before transmission. It may compress and decompress data to improve the throughput, and may encrypt and decrypt data to improve security. Compression/decompression and encryption/decryption may also be done at lower layers.

Layer 5

The session layer establishes, manages, and terminates sessions between two communicating hosts, to allow them to exchange data over a prolonged time period. The session layer is mainly concerned with issues that application processes may encounter and not with lower layer connectivity issues. The sessions, also called dialogs, can determine whether to handle data in both directions simultaneously or only handle data flow in one direction at a time. It also takes care of checkpoints and recovery mechanisms. The session layer is explicitly implemented with applications that use remote procedure calls.

Layer 4:

The transport layer defines segmenting and reassembling of data belonging to multiple individual communications, defines the flow control, and defines the mechanisms for reliable transport, if required. The transport layer serves the upper layers, which in turn interface with many user applications. To distinguish between these application processes, the transport layer uses its own addressing. This addressing is valid locally, within one host, unlike addressing at the network layer. The transport services can be reliable or unreliable. The selection of the appropriate service depends on application requirements. For instance, file transfer may be reliable, to guarantee that the file arrives intact and whole. On the other hand, a missing pixel when watching a video might go unnoticed. In networking, this is called an unreliable service.

Link layer

This layer is also known as the media access layer. It defines protocols used to interface the directly connected network. Tasks of the protocols at this layer are closely related to the characteristics of the physical medium and deal primarily with physical network details. The link layer is also referred to as a network interface, network access, or even data link layer. Because there are many different types of physical networks, there are many link layer protocols. An example of the TCP/IP link layer protocol is Ethernet. The link layer introduces physical addresses, sometimes called hardware addresses, to identify devices sharing a particular physical network segment.

Internet Layer

This layer routes data from the source to the destination, provides a means to obtain information on how to reach other networks, and deals with reporting of errors. The Internet layer provides logical addressing. Logical addressing ensures that a host is uniquely identified. An Internet layer logical address, called IP address, is used to identify a host. This address is valid globally and aims at uniquely identifying the host. End devices, such as laptops, mobile phones, and servers, are configured with a logical address, before they can connect to the network. IP protocols, namely IP version 4 (IPv4), and the newer version IP version 6 (IPv6), reside in this layer. This layer serves the upper Transport layer and passes information to the Link layer.

Which layer in the OSI model provides path connectivity beyond the local segment?

network layer

ISO

the International Organization for Standardization, is an independent, nongovernmental organization. It is the world's largest developer of voluntary international standards. Those standards help businesses to increase productivity while minimizing errors and waste.