My professor told me that the questions were based only on layer 2. No IP, layer
ID: 673169 • Letter: M
Question
My professor told me that the questions were based only on layer 2. No IP, layer 2 frame. What part of my work should I change ?
1)What is the primary purpose of a LAN?
The purpose of a local area network is to establish a communications network that connects computers, workstations, printers and other deceives that are being placed in a building or campus. Devices that are connected on a LAN are able to communicate with each other. The most popular LAN is an Ethernet. LANs have progressed over time because software use to be very expensive and difficult to install. Node devices, on the intermediate level, like repeaters, bridges and switches, allow LANS to be connected together to create larger LANS. A backbone, at the local level, is one or more lines that LAN’s can connect to in order to establish a WAN connection or to have a LAN span distances efficiently. In today’s society, Windows and Apple software and computers are created with LAN software built in.
2)A protocol is a collection of rules used to govern the format of messages that are being exchanged between computers and people. A protocol is also a standard procedure that two devices accept and use to understand each other. An example would be when computers communicate with each other by transferring data. The three basic types of protocol are character-oriented, byte-oriented and bit-oriented. Protocols can break a file into equal portions known as blocks or packets. When packets are being sent from a computer, the computer on the receiving end checks the packet and send an acknowledgment to the sending computer if the transportation of the block was successful. Protocol has a mathematical way of determining if a block was sent successfully or an error has occurred. A block will continue to be retransmitted until it successfully meets its destination. An example of a layer 2 protocol would be point to point protocol (PPP). PPP has the ability to simultaneously transmit multiple layer 3 protocols by using control protocols.
3) A MAC protocol is a procedure used to have control over a medium that is being utilized between a couple or more entities. The goal of the MAC protocol is to resolve any issues pertaining to independent entities competing with each other for access. Mac Protocols can either be contention based or schedule based. In contention based MAC protocols, there is distribution within the medium access. Central coordination for the nodes to use the medium is not necessary. In schedule based MAC protocols, noes are allowed to communicate in selected time slots and are left inactive at other times. An example of a contention based MAC protocol would be S-MAC. S-MAC works by have a node placed in a state that allows it to listen to a medium. If nothing is heard on that medium, a nod will send SYNC packet that contains a schedule that establishes definite listening and sleeping periods. The schedule will ultimately be adopted by all nodes that have heard that packet. An example of a schedule based MAC protocol would be LEACH (Low-Energy Adaptive Clustering Hierarchy). LEACH works in several rounds. A cluster head is elected once nodes are organized into clusters.
4) A frame is a packet. It is a term very specific to a number of data communication protocols. It represents a larger set of data. For example image information. When a large file is being prepared for transmission, it is divided into smaller units. The frame format is comprised of a header, payload and a trailer. Frames are specific to certain bit-oriented data transmission protocols. For example SDLC (synchronous Data Link Control). SDLC is a data communications line protocol that is linked with IBM systems network architecture.
5) Mac addresses are location independent. They are aligned with the card that fits inside a workstation, printer or server, which have the ability to move around. In the header of the LAN packet destination and source MAC names are being contained and can be used by different devices to filter through and continue to forward packets. Some examples of devices with this ability would be bridges, hubs and switches.
Explanation / Answer
Data Link Layer:(OSI Reference Model Layer 2)
The second-lowest layer in the OSI Reference Model stack is the data link layer, often abbreviated “DLL” (though that abbreviation has other meanings as well in the computer world). The data link layer, also sometimes just called the link layer, is where many wired and wireless local area networking (LAN) technologies primarily function. For example, Ethernet, Token Ring, FDDI and 802.11 (“wireless Ethernet” or “Wi-Fi’) are all sometimes called “data link layer technologies”. The set of devices connected at the data link layer is what is commonly considered a simple “network”, as opposed to an internetwork.
Data Link Layer Sublayers: Logical Link Control (LLC) and Media Access Control (MAC)
The data link layer is often conceptually divided into two sublayers: logical link control (LLC) and media access control (MAC). This split is based on the architecture used in the IEEE 802 Project, which is the IEEE working group responsible for creating the standards that define many networking technologies (including all of the ones I mentioned above except FDDI). By separating LLC and MAC functions, interoperability of different network technologies is made easier, as explained in our earlier discussion of networking model concepts.
Data Link Layer Functions
The following are the key tasks performed at the data link layer:
Logical Link Control (LLC): Logical link control refers to the functions required for the establishment and control of logical links between local devices on a network. As mentioned above, this is usually considered a DLL sublayer; it provides services to the network layer above it and hides the rest of the details of the data link layer to allow different technologies to work seamlessly with the higher layers. Most local area networking technologies use the IEEE 802.2 LLC protocol.
Media Access Control (MAC): This refers to the procedures used by devices to control access to the network medium. Since many networks use a shared medium (such as a single network cable, or a series of cables that are electrically connected into a single virtual medium) it is necessary to have rules for managing the medium to avoid conflicts. For example. Ethernet uses the CSMA/CD method of media access control, while Token Ring uses token passing.
Data Framing: The data link layer is responsible for the final encapsulation of higher-level messages into frames that are sent over the network at the physical layer.
Addressing: The data link layer is the lowest layer in the OSI model that is concerned with addressing: labeling information with a particular destination location. Each device on a network has a unique number, usually called a hardware address or MAC address, that is used by the data link layer protocol to ensure that data intended for a specific machine gets to it properly.
Error Detection and Handling: The data link layer handles errors that occur at the lower levels of the network stack. For example, a cyclic redundancy check (CRC) field is often employed to allow the station receiving data to detect if it was received correctly.
Physical Layer Requirements Definition and Network Interconnection Device Layers
As I mentioned in the topic discussing the physical layer, that layer and the data link layer are very closely related. The requirements for the physical layer of a network are often part of the data link layer definition of a particular technology. Certain physical layer hardware and encoding aspects are specified by the DLL technology being used. The best example of this is the Ethernet standard, IEEE 802.3, which specifies not just how Ethernet works at the data link layer, but also its various physical layers.
Since the data link layer and physical layer are so closely related, many types of hardware are associated with the data link layer. Network interface cards (NICs) typically implement a specific data link layer technology, so they are often called “Ethernet cards”, “Token Ring cards”, and so on. There are also a number of network interconnection devices that are said to “operate at layer 2”, in whole or in part, because they make decisions about what to do with data they receive by looking at data link layer frames. These devices include most bridges, switches and barters, though the latter two also encompass functions performed by layer three.
Some of the most popular technologies and protocols generally associated with layer 2 are Ethernet, Token Ring, FDDI (plus CDDI), HomePNA, IEEE 802.11, ATM, and TCP/IP's Serial Link Interface Protocol (SLIP) and Point-To-Point Protocol (PPP).
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.