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Group 2, Use, Provider, Protocol Used for Retrieval, Operation - Coggle…
Group 2
5. Describe the purpose of ARP
DEFINITION
Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever-changing Internet Protocol (IP) address to a fixed physical machine address, also known as a media access control (MAC) address, in a local-area network (LAN).
BASIC FUNCTION
Resolving IPv4 addresses to MAC
addresses
Maintaining a table of mappings
TYPES OF ARP
Proxy ARP.
Proxy ARP is a technique by which a proxy device on a given network answers the ARP request for an IP address that is not on that network. The proxy is aware of the location of the traffic's destination and offers its own MAC address as the destination.
Reverse ARP (RARP)
Gratuitous ARP is almost like an administrative procedure, carried out as a way for a host on a network to simply announce or update its IP-to-MAC address. Gratuitous ARP is not prompted by an ARP request to translate an IP address to a MAC address.
Gratuitous ARP.
Host machines that do not know their own IP address can use the Reverse Address Resolution Protocol (RARP) for discovery.
Inverse ARP.
Whereas ARP uses an IP address to find a MAC address, IARP uses a MAC address to find an IP address.
1. The purpose and function of the data link layer for transmission on specific media
Data Encapsulation
Message Segmentation
Large streams of data are divided into smaller, more manageable pieces to send over the network.
◦ By sending smaller pieces, many different conversations can be interleaved on the network, called multiplexing
◦ Each piece must be labelled
◦ If part of the message fails to make it to the destination, only the missing pieces need to be retransmitted.
Protocol Data Units
As application data is passed down the protocol stack, information is added at each level. This is known as the encapsulation process.
The form that the data takes at each layer is known as a Protocol Data Unit (PDU).
◦ Data - application layer PDU
◦ Segment – Transport layer PDU
◦ Packet – Network layer PDU
◦ Frame – Data Link Layer PDU
◦ Bits – Physical Layer PDU
Encapsulation Example
The encapsulation process works from top to bottom:
◦ Data is divided into segments.
◦ The TCP segment is encapsulated in the IP Packet.
◦ The IP packet is encapsulated in the Ethernet Frame.
De-encapsulation
De-encapsulation is the process used by a receiving device to remove one or more of the protocol headers.
◦ The data is deencapsulated as it moves up the stack toward the end-user application.
The de-encapsulation process works from bottom to top.
Data Access
Network Addresses
Network layer source and destination addresses - Responsible for delivering the IP packet from the original source to the final destination.
◦ Source IP address - The IP address of the sending device, the original source of the packet.
◦ Destination IP address - The IP address of the receiving device, the final destination of the packet.
Data Link Addresses
The purpose of the data link address is to deliver the data link frame from one network interface to another network interface on the same network.
◦ As the IP packet travels from source to destination it is encapsulated in a new data link frame when it is forwarded by each router
Devices on the Same Network
The network layer addresses, or IP addresses, indicate the original source and final destination.
◦ Network portion – The left-most part of the address indicates which network the IP address is a member of.
◦ Host portion – The remaining part of the address identifies a specific device on the network.
The data link frame which uses MAC addressing, is sent directly to the receiving device.
◦ Source MAC address - address of sending device.
◦ Destination MAC address – address of receiving device.
Devices on a Remote Network
Sending to a remote network - the source and destination IP addresses represent hosts on different networks.
The data link frame cannot be sent directly to the remote destination host. Therefore the frame is sent to the default gateway (nearest router interface).
The router removes the received Layer 2 information and adds new data link information before forwarding out the exit interface.
6. Explain why the IPv4 protocol requires other layers to provide reliability
• Internet Protocol Version 4 (IPv4) is protocol in data communication over different kinds of network. IPv4 is a connectionless protocol used in packet-switched layer network, such as Ethernet.
• It provides the logical connection between network devices by providing identification for each device.
• IPv4 is uses 32-bit addresses to Ethernet communication in five classes: A, B, C, D and E.
• Classes A, B and C have a different bit length for addressing the network host.
• Classes D, addresses are reserved for multicasting.
• Classes E, addresses are reserved for future use.
7. Explain how the ARP process in sending packet to a destination network
At the network layer when the source wants to find out the MAC address of the destination device it first looks for the MAC address (Physical Address) in the ARP cache or ARP table. If present there then it will use the MAC address from there for communication. If you want to view your ARP cache (in Windows Operating System) then open Command Prompt and type command-‘arp-a’ (without quotes).
The source device will broadcast the ARP request message to the local network.
The broadcast message is received by all the other devices in the LAN network. Now each
device will compare the IP address of the destination with its own IP address. If the IP address of destination matches with the device’s IP address, then the device will send an ARP reply massage. If the IP address do not match then the device will simply drop the packet.
The device whose IP address has matched with the destination IP address in the packet will reply and send the ARP reply message. This ARP replay message contains the MAC address of this device. The destination device updates it’s ARP table and stores the MAC address of the source as it will need to contact the source soon. Now, the source becomes destination (target) for this device and the ARP Reply message is sent.
When the source receives the ARP reply it comes to know about the destination. MAC address and it also updates its ARP cache. Now the packets can be sent as the source how address.
2. Describe the basic characteristics of media access control methods on WAN and LAN topologies
DATA LINK PROTOCALS
Purpose of the Data Link Layer
data link layer
Layer 2 Data Link Addresses
The Layer 2 notation for network devices connected to a common medium is called a node.
Specifically the data link layer performs these two basic services:
It accepts Layer 3 packets and packages them into data units called frames
It controls media access control and performs error detection
The data link layer effectively separates the media transitions that occur as the packet is forwarded from the communication processes of the higher layers. The data link layer receives packets from and directs packets to an upper layer protocol, in this case IPv4 or IPv6. This upper layer protocol does not need to be aware of which media the communication will use.
Data Link Sublayers
Logical Link Control (LLC)
◦ Communicates with the network layer.
◦ Identifies which network layer protocol is being used for the frame.
◦ Allows multiple Layer 3 protocols, such as IPv4 and IPv6, to utilize the same network interface and media.
Media Access Control (MAC)
◦ Defines the media access processes performed by the hardware.
◦ Provides data link layer addressing and access to various network technologies.
◦ Communicates with Ethernet to send and receive frames over copper or fiber-optic cable.
◦ Communicates with wireless technologies such as Wi-Fi and Bluetooth.
Media Access Control
As packets travel from the source host to the destination host, they travel over different physical networks.
As packets travel from the source host to the destination host, they travel over different physical networks.
Physical networks can consist of different types of physical media such as copper wires, optical fibers, and wireless consisting of electromagnetic signals, radio and microwave frequencies, and satellite links.
Providing Access to Media
At each hop along the path, a router:
• Accepts a frame from a medium
• De-encapsulates the frame
• Re-encapsulates the packet into a new frame
• Forwards the new frame appropriate to the medium of that segment
Data Link Layer Standards
Engineering organizations that define open standards and protocols that apply to the network access layer include:
◦ Institute of Electrical and Electronics Engineers (IEEE)
◦ International Telecommunication Union (ITU)
◦ International Organization for Standardization (ISO)
◦ American National Standards Institute (ANSI)
MEDIA ACCESS CONTROL
Topologies
Controlling Access to the Media
Media access control is the equivalent of traffic rules that regulate the entrance of motor vehicles onto a roadway.
The absence of any media access control would be the equivalent of vehicles ignoring all other traffic and entering the road without regard to the other vehicles.
However, not all roads and entrances are the same. Traffic can enter the road by merging, by waiting for its turn at a stop sign, or by obeying signal lights. A driver follows a different set of rules for each type of entrance.
Physical and Logical Topologies
Physical Topologies
Refers to the physical connections and identifies how end devices and infrastructure devices such as routers, switches, and wireless access points are interconnected
Logical Topologies
Refers to the way a network transfers frames from one node to the next. These logical signal paths are defined by data link layer protocols.
WAN Topologies
Common Physical WAN Topologies
Point-to-Point - Permanent link
between two endpoints
Hub and Spoke - A central site interconnects branch sites using point-to-point links
Mesh - Provides high availability, but requires that every end system be interconnected to every other system. Administrative and physical costs
Physical Point-to-Point Topology
Frames are placed on the media by the node at one end and taken from the media by the node at the other end of the point-to- point circuit
Logical Point-to-Point Topology
• End nodes communicating in a point-to-point network can be physically connected via a number of intermediate devices.
• However, the use of physical devices in the network does not affect the logical topology.
• The logical connection between nodes forms what is called a virtual circuit.
LAN Topologies
Physical LAN Topologies
Star
End devices are connected to a central intermediate device. Use Ethernet switches.
Extended Star
Additional Ethernet switches interconnect other star topologies.
Bus
Used in legacy networks. All end systems are chained to each other and terminated in some form on each end. Switches are not required to interconnect the end devices. Bus topologies using coax cables were used in legacy Ethernet networks because it was inexpensive and easy to set up.
Ring
End systems are connected to their respective neighbor forming a ring. Unlike the bus topology, the ring does not need to be terminated. Ring topologies were used in legacy Fiber Distributed Data Interface (FDDI) and Token Ring networks
Half and Full Duplex
Half-Duplex Communicatio
◦ Both devices can transmit and receive on the media but cannot do so simultaneously.
◦ Used in legacy bus topologies and with Ethernet hubs.
◦ WLANs also operate in half-duplex.
Full-Duplex Communication
◦ Both devices can transmit and receive on the media at the same time.
◦ Data link layer assumes that the media is available for transmission for both nodes at any time.
◦ Ethernet switches operate in full-duplex mode by default, but can operate in half-duplex if connecting to a device such as an Ethernet hub
Media Access Control Methods
Contention-Based Access
◦ Nodes operate in half- duplex.
◦ Compete for the use of the medium.
◦ Only one device can send at a time
Controlled Access
◦ Each node has its own time to use the medium.
◦ Each node has its own time to use the medium.
◦ Legacy Token Ring LANs are an exam
Contention-based Access - CSMA/CD
Carrier Sense Multiple Access/Collision Detection (CSMA/CD) process is used in half- duplex Ethernet LANs.
◦ If two devices transmit at the same time, a collision will occur.
◦ Data sent by both devices will be corrupted and will need to be resent
◦ Both devices will detect the collision on the network.
CSMA/CA
◦ Uses a method to detect if the media is clear.
◦ Does not detect collisions but attempts to avoid them by waiting before transmitting.
Note: Ethernet LANs using switches do not use a contention-based system because the switch and the host NIC operate in full-duplex mode.
3. Describe the characteristics and functions of the data link frame.
Data Link Frame
The Frame
Each frame type has three basic parts:
◦ Header
◦ Data
◦ Trailer
structure of the frame and the fields contained in the header and trailer depend on Layer 3 protocol.
Frame Fields
Frame start and stop indicator
flags
Identifies the beginning
and end limits of the frame
Addressing
Indicates the
source and destination node
Type
Identifies the Layer 3
protocol in the data field
Control
Identifies special flow
control services such as QoS.
Data
Contains the frame payload (i.e., packet header, segment header, and the data)
Layer 2 Addresses
Each data link frame contains the source data link address of the NIC card sending the frame, and the destination data link address of the NIC card receiving the frame.
LAN and WAN Frames
Layer 2 protocol used for a topology is determined by the technology.
Data link layer protocols include:
◦ Ethernet
◦ 802.11 Wireless
◦ Point-to-Point Protocol (PPP)
◦ HDLC
◦ Frame Relay
4. Differentiate the roles of the MAC address and the IP address
MAC Address
The term MAC address is an acronym for Media Access Control Address. The MAC Address refers to a unique identifier that gets assigned to a Network Interface Card/ Controller (NIC). It has a 64-bit or 48-bit address linked and connected to the concerned network adapter. The MAC Address can exist in a hexadecimal format. This type of address exists in six separate sets of two characters/ digits – separated from each other using colons.
The primary use of a MAC address is to ensure the physical address of a given device/ computer.
The Manufacturer of NIC Cards provides a device with its MAC address.
You can retrieve a device attached to the MAC address using the ARP protocol.
The MAC address primarily operates on the data link layer.
IP Address
The term IP Address is an acronym for Internet Protocol Address. An IP Address refers to the address that assists a user in identifying a network connection. It also goes by the Logical Address name provided to individual connections in the present network. An IP address lets us understand and control the way in which various devices communicate on the Internet. It also defines the specific behavior of various Internet routers.
The IP address, on the other hand, defines a computer’s logical address.
An ISO (Internet Service Provider) provides a device’s IP address.
You can retrieve a device attached to the IP address using the RARP protocol.
The IP address primarily operates on the network layer.
Use
Provider
Protocol Used for Retrieval
Operation
