Linking Computer Network Devices to CMDB Classes in ServiceNow

[SrikrishnaB5625]

Nodes:

Nodes are devices that are connected to a network.

Protocol: 

A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols include TCP/IP, HTTP, and FTP.

Topology: 

Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh, and tree.

IP Address:

An IP address is a unique numerical identifier identifies a device globally on the internet. Internet service providers (ISPs) typically assign IP addresses to devices that connect to the internet.

IPv4 address is 32 bits, hence, we have 232 IP addresses available. The length of an IPv6 address is 128 bits. “Ipconfig”

Mac Address:

A MAC address identifies a device locally on a network. The manufacturer of the device's network interface controller (NIC) provides the MAC address.

 “ipconfig/all”

Service Provider Networks:

These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider.

Internet service provider: Data retrieved in mobiles from internet

DNS: 

The Domain Name System (DNS) is a protocol that is used to translate human-readable domain names (such as www.google.com) into IP addresses that computers can understand.

Open system: 

A system that is connected to the network and is ready for communication. 

Closed system: 

A system that is not connected to the network and can’t be communicated with.

Access Point:

An access point in networking is a device that allows wireless devices, like smartphones and laptops, to connect to a wired network.

Modems :

Modems is also known as modulator/demodulator is a network device that is used to convert  into analog signal of different frequencies and transmits these signal to a modem at the receiving location.

A modem connects your network to the internet by converting data between digital signals (used by devices) and analog signals (used by the internet provider).

Firewall:

A firewall is a network security device or software that monitors and controls incoming and outgoing network traffic based on predefined security rules. It acts as a barrier between a trusted internal network and untrusted external networks like the internet. - It is both virtual and physical.

Repeater

A repeater operates at the physical layer. Its main function is to amplify (i.e., regenerate) the signal over the same network before the signal becomes too weak or corrupted to extend the length to which the signal can be transmitted over the same network. 

Hub

hub sends data to all connected devices, which can slow down the network. - physical layer - broadcasting

A hub is a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology - active, passive  and intelligent.

Bridge

A bridge operates at the data link layer. A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of the source and destination. It is also used for interconnecting two LANs working on the same protocol. - Transparent and source routing bridges.

Switch

A switch sends data only to the specific device that needs it based on MAC address.

A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. 

A switch is a data link layer device. The switch can perform error checking before forwarding data, which makes it very efficient as it does not forward packets that have errors and forward good packets selectively to the correct port only. 

Router

A router is a device like a switch that routes data packets based on their IP addresses. The router is mainly a Network Layer device. Routers normally connect LANs and WANs and have a dynamically updating routing table based on which they make decisions on routing the data packets.

Gateway

A gateway, as the name suggests, is a passage to connect two networks that may work upon different networking models. Gateways are also called protocol converters and can operate at any network layer.

Brouter

both bridge and router. It can work either at the data link layer or a network layer. Working as a router, it is capable of routing packets across networks and working as the bridge

Network interface

A network interface is what your OS uses to send and receive data over a network — it could be physical (via NIC) or virtual.

NIC

NIC or network interface card is a network adapter that is used to connect the computer to the network.

Port:

Port is a logical address of a 16-bit unsigned integer that is allotted to every application on the computer that uses the internet to send or receive data.

subnet mask

A subnet mask is used in IP addressing to divide the network into sub-networks, or subnets. It helps determine which portion of an IP address is the network address and which part is the host address.

NAT (Network Address Translation)?

NAT is a method used by routers to translate private IP addresses within a local network to a public IP address before sending data over the internet. This helps to conserve IP addresses and add a layer of security by hiding internal network addresses.

Virtual Machine instance

A Virtual Machine instance is a virtualized computer that runs within a host system, enabling users to operate multiple isolated operating systems on a single physical machine.

Network gear, server, load balancer

Ssh, Wmi, snap, powershelgl, cim, vm appliance

What is OSI Model? – Layers of OSI Model

The OSI (Open Systems Interconnection) Model is a set of rules that explains how different computer systems communicate over a network. OSI Model was developed by the International Organization for Standardization (ISO). 

Physical Layer

Physical Layer is responsible for transmitting individual bits from one node to the next. - Hub, repeater, Modem, cables

Bit Synchronization:  by providing a clock. Bit Rate Control

Physical Topologies: how the different, devices/nodes are arranged in a network i.e. bus topology, star topology, or mesh topology.

Transmission Mode:  how the data flows between the two connected devices I.e  Simplex, half-duplex and full duplex. Half data transfer not at a time.

Data Link Layer (DLL)

The data link layer is responsible for the node-to-node delivery of the message. Ensures data transfer is error-free.

The Data Link Layer is divided into two sublayers:

• Logical Link Control (LLC)
• Media Access Control (MAC). Organizational Unique Identifier, The rightmost six digits represent Network Interface Controller, which is assigned by the manufacturer. 

The packet received from the Network layer is further divided into frames depending on the frame size of the NIC (Network Interface Card). DLL also encapsulates Sender and Receiver’s MAC address in the header.

The Receiver’s MAC address is obtained by placing an ARP (Address Resolution Protocol) request onto the wire asking, “Who has that IP address?” and the destination host will reply with its MAC address.

Framing: attaching special bit patterns to the beginning and end of the frame.

Physical Addressing: MAC addresses of the sender and/or receiver in the header of each frame.

Error Control. Flow Control. Access Control:  control over the channel at a given time.

 Network Layer

The network layer works for the transmission of data from one host to the other located in different networks. packet routing. The sender and receiver’s IP address are placed in the header by the network layer. Segment in the Network layer is referred to as Packet.-routers and switches.

Routing. Logical Addressing.

Transport Layer

Data is in Segments. It is responsible for the end-to-end delivery of the complete message. Protocols used in Transport Layer are TCP, UDP NetBIOS, PPTP. At the sender’s side, the transport layer receives the formatted data from the upper layers, performs Segmentation, and also implements Flow and error control to ensure proper data transmission. It also adds Source and Destination port number in its header and forwards the segmented data to the Network Layer.

At the Receiver’s side, Transport Layer reads the port number from its header and forwards the Data which it has received to the respective application. It also performs sequencing and reassembling of the segmented data.

Segmentation and Reassembly. Service Point Addressing.

Services Provided by Transport Layer

Connection oriented - Tcp

Connectionless oriented - Udp

Session Layer

It  provides authentication and security. Protocols used in the Session Layer are NetBIOS, PPTP. Connection establishment.

Session Establishment, Maintenance, and Termination. Synchronization: This layer allows a process to add checkpoints

Dialog Controller: The session layer allows two systems to start communication with each other in half-duplex or full duplex.

Presentation Layer

The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network. Protocols used in the Presentation Layer are JPEG, MPEG, GIF, TLS/SSL, etc.

Translation: For example, ASCII to EBCDIC.

Encryption/ Decryption: The encrypted data is known as the ciphertext, and the decrypted data is known as plain text. A key value is used for encrypting as well as decrypting data.

Compression: Reduces the number of bits that need to be transmitted on the network.

Application Layer

This layer also serves as a window for the application services to access the network and for displaying the received information to the user. Protocols used in the Application layer are SMTP, FTP, DNS, etc.

Network Virtual Terminal (NVT): It allows a user to log on to a remote host.

PROTOCOLS:

• Transmission Control Protocol/Internet Protocol (TCP/IP):TCP Ensures data is delivered reliably and in order and IP routes data packets to their destination based on IP addresses.
• UDP (User Datagram Protocol): A connectionless protocol that does not guarantee delivery or order. It is used for applications where speed is more important than reliability, like streaming and gaming.
• Hypertext Transfer Protocol (HTTP) and HTTPS: transmitting web pages.  HTTPS secured communication using SSL/TLS encryption.
• Simple Mail Transfer Protocol (SMTP):  SMTP protocol works with other protocols like POP3 and IMAP for email retrieval.
• File Transfer Protocol (FTP): 
• Dynamic Host Configuration Protocol (DHCP): DHCP protocol automatically assigns IP addresses to devices on a network.
• Domain Name System (DNS): DNS Translates human-friendly domain names into IP addresses. Ensures seamless navigation on the internet.
• ARP: ARP stands for Address Resolution Protocol. It is used to convert an IP address to its corresponding physical address(i.e., MAC Address). ARP is used by the Data Link Layer to identify the MAC address of the Receiver’s machine. 
• RARP: RARP stands for Reverse Address Resolution Protocol. As the name suggests, it provides the IP address of the device given a physical address as input. But RARP has become obsolete since the time DHCP has come into the picture.

Circuit Switching  dedicated communication path is established for the entire communication session. Traditional telephone networks (PSTN).

Message Switching entire message is sent to an intermediate node, stored, and forwarded until it reaches the destination.Email systems.q

Packet Switching data is divided into packets that are routed independently to the destination.  The Internet (TCP/IP).

large networks (Class A), medium-sized networks (Class B), small networks (Class C), multicasting (Class D), and experimental use (Class E); 

[Mark Manders]

You are posting this in the question part of the ServiceNow Community. What is the purpose of this post? I see a lot of definitions, but no question or anything related to ServiceNow.