Network Fundamentals: Models, Hardware, Addressing, and Protocols

Network

a group of computers and other devices connected by some type of transmission device

Topology

How the parts of a whole work together

Physical Topology

How devices are connected physically through wiring

Logical Topology

How to access a network, use software, how users gain access, and how specific resources are shared

Peer to peer network model

No server; The OS of each computer on the network is responsible for controlling its own resources, security, and administration

Cons of Peer to Peer Network Model

Not scalable; Not very secure due to the lack of a central server

Client-server network model

Resources are accessed via a centralized directory database managed by the NOS (network operating systems)

Domain

the group of computers whose network access is controlled by a server

Client

a computer making a request to another

Networking Operating System (NOS)

control access to the entire network

Scalability

ability to increase the size and add/remove elements of a network

Active Directory

centralized directory database that contains user account information and security for the entire group of computers

Active Directory Domain Services

manages the process of how users sign on to the network and get access to resources of the AD

Server

any computer or program that provides a service

LAN

Local area network

Switch

Receives incoming data from one of its ports and redirects it to 1 or more ports that will send the data to its intended destination; Uses MAC address to identify devices; Works at layer 2 of the OSI model; Use ethernet to transmit data; Contains the MAC address of the sender and the receiver

Hub

Physical device that transmits data to all devices on a network; Works at layer 1 of the OSI model

Router

Manages traffic between multiple networks; Used in SOHO (small office-home office) networks to connect the LAN to the internet

WAN

A group of LANs spread over a wide geographical area

Metropolitan area network (MAN/CAN)

A group of connected LANS in the same geographical area

PAN

Network of personal devices; Smallest network

OSI Model (Open System Interconnect)

A conceptual framework used to understand network interactions in seven layers.

Transport Layer

Purpose is to guarantee that information is transmitted; Can also slow down or speed up a message

TCP (Transmission Control Protocol)

makes a connection with the end host, checks whether data is received, and resends if needed

UDP (User Datagram Protocol)

used for broadcasting, where delivery is not as important as fast transmission.

Datagram

A message

Segments

A split message

Port addresses

2 port addresses are added to the message (new header).

HTTP port

port #80.

Session layer

Responsible for how data between applications are synced and recovered if messages don't arrive intact at the receiving application.

API call

Method an application uses when it makes a request of the OS.

Presentation layer

Responsible for reformatting, compressing, and/or encrypting data.

Application layer

The interface between two applications on separate computers.

HTTP application layer protocol

Applications that provide services to a user use HTTP application layer protocol.

Utility programs

Utility programs that provide services to the system.

Payload

Data

Structured cabling

Standard is known as structured cabling.

Entrance facility

The location where an incoming network, such as the Internet, connects with the school or corporate network.

Demarc

The device that marks where a telecommunications service provider's network ends and the organization's network begins.

MDF

The centralized point of interconnection for an organization's LAN or WAN.

Data room

the enclosed space that holds network equipment.

Patch panel

A panel of data receptors that provide a central termination point when many patch cables converge.

IDF

Provides an intermediate connection between the MDF and end-user equipment on each floor and in each building.

Patch cable

Short cabling used with connectors.

Backbone cables

Backbone consists of cables or wireless links that provide interconnection between the entrance facility and MDF, and between the MDF and IDFs.

Straight through

Same wiring order and connects two different devices.

Cross-over cables

Different order of wires and used to connect the same device.

Bend radius

The max radius a cable can bend before damaging the wires.

Network diagrams

Graphical representations of a network's devices and connections.

Nmap

An open-source network scanning tool used for network exploration and security auditing.

MAC address

Embedded on every NIC and are six hex numbers separated by colons.

Internet Protocol version 4 (IPv4)

addresses 32 bits and are 4 decimal numbers called octets.

Internet Protocol version 6 (IPv6)

128 bits and written as eight blocks of hex numbers.

Ports

A number used to find an application.

FQDNs

Fully qualified domain names are assigned to every host on a network and are unique.

Domain name

The last two parts of a host's name.

Host name

The first part of a host's name.

Static IP Addresses

Permanently assigned to a device.

Dynamic IP Addresses

Requested and received by a device from a DHCP server.

Dynamic Host Configuration Protocol (DHCP)

manages the dynamic distribution of IP addresses to devices on a network.

Gateways

Computer routers or a device that a host uses to access another network.

Subnet masks

a 32-bit number that separates an IP address into a network portion and a host portion

Ipconfig

Used to find the current TCP/IP settings.

Classful addressing

5 classes: A-E, where Class A-C are available for internet use and are public.

Network Address Translation (NAT)

a technique designed to conserve the number of public IP addresses needed by a network.

Static Network Address Translation (SNAT)

the gateway assigns the same public IP to a host each time it makes a request.

Destination Network Address Translation (DNAT)

process where a host outside the network addresses a computer inside using a predetermined IP address.

Address translation

The process where a gateway device substitutes the private IP address with its own public address.

Port address translation (PAT)

process of assigning a TCP port number to each ongoing session between a local host and internet host.

Unicast addresses

Specifies a single node.

Global addresses

Can be routed on the internet

Link local addresses

Used for communications with nodes in the same link.

Multicast address

Delivery packets to all nodes in the targeted multicast group.

Anycast address

Identifies multiple destinations and delivers packets to the closest one.

Socket

Both a host's IP address and a process's TCP or UDP port separated by two values.

Standard port for Telnet

port 23.

Socket address for Telnet

10.43.3.87:23

Port range

#'s from 0 to 65535.

Well-known ports

ports from 0 to 1023.

Internet Assigned Numbers Authority (IANA)

Assigns port numbers

Registered ports

ports from 1024 to 49151.

Dynamic and private ports

range from 49152 to 65535

Dynamic ports

assigned by a client or server as the need arises.

Private ports

assigned by network admin.

Trivial File Transfer Protocol (TFTP)

Most commonly used by computers (without user intervention) as they are booting up to request configuration files from another computer on the local network.

Network Time Protocol (NTP)

A simple protocol used to synchronize clocks on computers throughout a network.

Lightweight Directory Access Protocol (LDAP)

A standard protocol for accessing network-based directories.

Server Message Block (SMB)

First used by earlier Windows OSes for file sharing on a network.

Session Initiation Protocol (SIP)

A signaling protocol that is used to make an initial connection between hosts but that does not participate in data transfer during the session.

H.323

Another signaling protocol used to make a connection between hosts prior to communicating multimedia data.

Top Level Domain (TLD)

The last part of an FDQN

DNS

An application layer client-server system of computers and databases.

Namespace

The entire collection of computer names and their associated IP addresses stored in databases on DNS servers around the globe.

Name servers

Computers that hold databases, organized in a hierarchical structure.

Resolvers

A DNS client that requests information from DNS name servers.

Primary DNS server

The authoritative name server for the organization and holds the authoritative DNS database.

Secondary DNS server

Backup ANS for the organization.

Caching DNS server

A server that accesses public DNS data and caches the DNS information it collects.

Forwarding DNS server

An optional server that receives queries from local clients but doesn't resolve the queries.

Recursive query

Demands a resolution or the answer 'It cant be found'.