Microsoft Networking Essentials 1

A LAN (local area network), as the name implies, comprises a group of computers contained within a small geographic area. WANs (wide area networks) connect LANs that are geographically distant. MANs (metropolitan area networks) are not confined to a small area; they are typically larger than a LAN but smaller than a WAN. There is no type of network called a CAN.

Error correction refers to the process of identifying and correcting errors that occur during data transmission. When packets are garbled or lost in transit, error correction techniques are used to detect and fix these errors. This ensures that the transmitted data is received accurately and without any corruption. Error correction mechanisms such as forward error correction (FEC) or error correcting codes (ECC) are commonly used in network protocols to ensure reliable data transmission.

Baseband technology can carry only one signal at a time. It is typically used in a local area network (LAN) environment where the medium is shared by all computers. An example of this is Ethernet or Token Ring. Only one system can transmit at a time, and that system’s signal is the only one that can occupy the communication channel or medium. Broadband technology, not baseband technology, can carry more than one signal at a time. An example of this is the cable television (CATV) network, which provides many channels over a single cable installation.

Flow control refers to the process of managing the rate of data transmission between a sender and a receiver. In this context, flow control involves the generation of messages by a receiving system to instruct the sending system to either speed up or slow down its transmission. This ensures that the receiver can handle the incoming data at a pace it can handle, preventing data loss or overload. Flow control is crucial in maintaining efficient and reliable communication between systems.

WANs (wide area networks) connect LANs that are geographically distant. A LAN, as the name implies, comprises a group of computers, not other LANs, and it is contained within a small geographic area. MANs (metropolitan area networks) connect LANs in a single metropolitan area; they are not confined to a small area. A MAN is typically larger than a LAN but smaller than a WAN. There is no type of network called a CAN.

Segmentation refers to the process of dividing lengthy data streams into smaller segments that can be transmitted over a network. This is necessary because large data streams may exceed the maximum transmission unit (MTU) size, causing network congestion or data loss. By segmenting the data, it becomes more manageable and can be efficiently transmitted across the network.

A WAN (wide area network) uses point-to-point connections between two systems to connect LANs (local area networks) that are geographically distant. A LAN connects a group of computers, not whole networks, over a common shared medium. There is no type of network called a VAN or a CAN.

Electrical signals transmit data over copper cable. Fiber-optic is a cable type, not a signal type. Microwave signals can’t be transmitted over copper cable. Infrared signals are used only for wireless networks.

Packet acknowledgment refers to the process of the recipient sending a return message to confirm that a packet or packets have been successfully received. This is an important aspect of communication protocols, as it allows the sender to ensure that the intended recipient has received the transmitted data. Without packet acknowledgment, there would be no way to verify if the data has been successfully delivered, leading to potential errors and data loss.

Error detection refers to the process of identifying and detecting errors in data transmission. In this context, the inclusion of special codes in a packet helps the receiving system verify whether the content of the packet has been damaged during transit. These special codes, often referred to as checksums or error detection codes, allow the receiving system to compare the received data with the calculated code to determine if any errors have occurred. This ensures the integrity and reliability of the transmitted data.

IEEE is responsible for developing and publishing standards that define data-link and physical layer standards. The ITU-T, formerly known as the CCITT, coordinates the development and advancement of international telecommunication networks and services. ANSI is a private organization that administers and coordinates a United States–based standardization and conformity assessment system. ISO developed and published the Open System Interconnection (OSI) model to serve as a conceptual model for software and hardware developers.

The illustration shows the process by which protocols at successive layers of the OSI model add headers to the data they receive from the layer above. This process is called data encapsulation. Packet switching is the process by which a system splits data into separate units called packets, which it individually transmits over the network. Media access control is the mechanism that specifies which computer is able to use the network at a particular time. Dialog separation is a session-layer process that calls for the creation of checkpoints that networked systems use to synchronize their activities.

The physical layer of the OSI model defines the standards for physical and mechanical characteristics of a network, such as cabling (copper and fiber), connecting hardware (hubs), and signaling methods (analog and digital). All other protocols reside above the physical layer of the OSI model.

The physical layer defines specific mechanical and electrical characteristics of a network. The data-link layer defines specific network—LAN or wide area network (WAN)—architectures and their characteristics. The physical layer standards you implement are dependent on the data-link layer protocol you select. All other layers reside above the physical and data-link layers.

The network medium provides the physical connection between networked computers. This connection can be made through copper-based, fiber-optic, or wireless technologies. The network medium is not a protocol, and only routing protocols and routers forward data packets. The network medium does not process electrical or light pulses and convert them to data; it carries only the signals generated by transceivers.

Presentation layer protocols are responsible for the formatting, translation, and presentation of information. No other layers of the OSI model translate and format application data.

Data-link layer protocols define the transmission and reception of frames. Hardware level addresses are included in each frame to identify the local sending and receiving systems. Ethernet uses the CSMA/CD channel access method. Physical layer specifications include the transmission of electrical or light pulses to represent 1s and 0s, not frames. Token passing is a data-link layer channel access method used exclusively by Token Ring.

Data encapsulation occurs when the transmitting system’s protocol stack packages information as it’s passed down from one layer to the next, preparing it for transmission across the network. The encapsulation process is performed by the sending host’s protocol stack. Each protocol layer on the sending host adds a header with control information as it’s passed down the stack in preparation for transmission on the network. Protocols use special codes, like a cyclical redundancy check (CRC), to allow for error checking. Protocol identification specifies the protocol that’s carried in a frame. Both the CRC and the protocol identification are included in the fields of information that are added during the encapsulation process. User data is the original raw information that must be encapsulated prior to transmission across the network.

LANs are packet switching networks, meaning that all communications are split into multiple packets that are individually transmitted over the network medium. As a result, multiple workstations can share the medium using baseband signaling; broadband is not necessary. Ethernet does run on coaxial cable, although this implementation is obsolete. Cable television networks do use broadband signaling on coaxial cable.

The application layer provides an entry point for applications to access the protocol stack and prepare information for transmission across a network. All other layers of the OSI model reside below this layer and rely on this access point.

The only layer that adds both a header and a footer (or trailer) is the data-link layer. The process of adding the headers and footers is referred to as data encapsulation. All other protocol layers add just a header (control information) as data is passed down to the next layer within the model. (

A connection-oriented transport layer protocol provides guaranteed delivery of information for upper-layer applications. Connectionless services do not guarantee delivery of information and therefore are not a good choice. Guaranteed delivery of information is generally not a function of the data-link, network, or application layer.

The session layer protocols are responsible for creating and maintaining a dialog between end systems. This dialog can be a two-way alternate dialog that requires end systems to take turns transmitting, or it can be a two-way simultaneous dialog where either end system can transmit at will. No other layers of the OSI model perform dialog control between communicating end systems.

Token Ring is a local area network (LAN) technology that uses baseband signaling (one signal on the channel) over a physical star topology, providing collision-free access to the medium. There are no collisions because Token Ring uses a token passing channel access method. Only the system holding the token has permission to transmit; all others must wait for the token. Fiber-optic is a cable type. Ethernet also uses baseband signaling and can operate in a physical star configuration; however, it is subject to collisions. IP is a connectionless network layer protocol responsible for logical source and destination addressing of hosts.

There are two types of transport layer protocols: connection-oriented and connectionless. Connection-oriented protocols guarantee the delivery of datagrams from source to destination by creating a connection between the sender and receiver before any data is transmitted. Connectionless protocols do not require a connection between end systems in order to pass datagrams. The physical layer does not use connectionless or connection-oriented protocols; it defines standards for transmitting and receiving information over a network. The network layer is responsible for logical addressing and routing. The session layer is responsible for creating and maintaining a dialog between end systems. The presentation layer is responsible for the formatting, translation, and presentation of information.

The network layer is responsible for connecting networks. A router is required to connect different data-link layer architectures such as Ethernet and Token Ring. A router is a network layer device. Routers use routing protocols to route datagrams across an internetwork. Fragmentation might need to be performed before the transmission of datagrams between different networks to accommodate the smallest acceptable datagram size of any link in the path. No other layers of the OSI model use routers to connect networks.

Network layer protocols identify logical addresses for communicating end systems and routing datagrams across a network. The physical layer defines standards for physical and mechanical characteristics of a network. The data-link layer uses Media Access Control (MAC) addresses, not logical addresses. The transport layer uses port addresses, not logical addresses. Session layer protocols create and maintain a dialog between end systems. The application layer provides an entry point for applications to access the protocol stack and prepare information for transmission across a network.