Computer Networks: Security, ISPs, and Reliability

Threats to Computer Security

• Spyware secretly collects user data from visited websites and is installed on network devices.

Network Types

• Extranets allow secure access to a corporate network ensuring customers, suppliers, and collaborators remain safe.
• Intranets provide a private connection of LANs and WANs belonging to an organization accessible to authorized members/employees.
• BYOD (Bring Your Own Device) enables end users to access the corporate network using personal tools, security and compatibility with corporate software/devices are major concerns.

Internet Service Providers (ISPs)

• ISPs are organizations that provide Internet access to businesses and individuals.

Network Reliability

• Fault tolerance is achieved using redundant links and devices.
• Scalability supports network expansion without degrading service.
• Security protects the network from unauthorized access.

Intranets

• An intranet is a private network, designed for employees, members or others inside an organization to access internal data
• In scenarios needing to access confidential data from internal servers at a head office, an intranet provides the necessary secure access

Powerline Networking

• Powerline networking connects devices to a network using adapters and existing electrical outlets, offering functionality where wireless access points are limited, not replacing physical cabling.

Network Security

• Network security ensures data confidentiality when confidential patient data is exposed on a wireless network.

Network Media Criteria

• Key factors for selecting network media include transmission distance and suitability for the environment.

Quality of Service (QoS)

• Video conferencing requires QoS as it uses real-time audio and video, this ensures continuous user experiences.

Home Network Minimum Security

• Basic security includes implementing a firewall and installing anti-virus software.

Cisco IOS Password Protection

• Passwords can protect the VTY and console interfaces
• Privileged EXEC mode and User EXEC Mode can be password protected

Layer 2 Switch Remote Management

• Remote management of a Layer 2 switch is facilitated through the switch virtual interface (SVI).

IOS Command Completion

• In Cisco IOS, pressing the Tab key completes partially typed commands.

Discarding Router Configuration Changes

• Discard changes not saved by using the reload command without saving, reverting to the NVRAM-stored file on reboot.

Interrupting IOS Processes

• Use Ctrl-Shift-6 key combination to interrupt an IOS process like ping or traceroute.

Switch Access Control Passwords

• Access user EXEC mode via the console connection of a switch using the line console 0 password.

Switch Configuration

• Configuring a switch with an IP address typically involves setting up a switch virtual interface (SVI) for remote management.

Command Hierarchy Navigation

• Returns to the previous command level with the exit command.

RAM Characteristics on Cisco Devices

• RAM stores the running configuration and loses contents during a power cycle.

Cisco IOS Host Naming Conventions

• Valid host names under Cisco IOS should start with a letter, contain no spaces, end with letter/digit, and use only letters, digits, and dashes; hostname cannot exceed 64 characters.
• RM-3-Switch-2A4 and SwBranch799 are valid hostnames

SSH and Telnet

• SSH encrypts messages, using user authentication, for secure remote sessions, whereas Telnet sends messages as plaintext and is considered insecure
• SSH provides security by encrypting messages
• Telnet transmits data in plaintext and sends messages in plaintext, thus less secured

IOS Modes of Operation

• IOS admin must follow user EXEC mode, privileged EXEC mode, global configuration mode, and line configuration mode to configure switch console port with a password

SVI Characteristics

• SVIs are essential for remote switch management over a network, created in software, and not tied to physical interfaces.

Verifying Interface Conditions

• Use the show ip interface brief command to check the status and IP address of switch interfaces.

Understanding IOS Modes

• User EXEC mode offers limited basic monitoring commands and serves as the entry point to the CLI.
• Privileged EXEC mode can be accessed through the enable command and is characterized by a prompt ending with a #.
• Changes affecting the device's operation are made in global configuration mode, accessed via the configure terminal command.

CLI Hotkeys and Shortcuts

• Tab completes commands.
• A question mark (?) provides context-sensitive help.
• The Up Arrow key scrolls backward through previous commands.
• Ctrl-Shift-6 interrupts IOS processes such as ping or traceroute.
• Space bar displays the next screen

IOS Command Syntax

• In the show running-config command, running-config is a keyword specifying what output to display.

Cisco Switch Configuration Changes

• Issuing a copy running-config startup-config command on a Cisco switch stores the new configuration in flash memory.

Password Encryption

• All passwords are prevented by the service password-encryption command from appearing in plain text in a configuration file

The Service Password Encryption Command

• Use the service password-encryption command to encrypt all cleartext passwords in the configuration files

Flow Control

• Flow control reduces the chance of dropped packets caused by data being sent too quickly
• Ensures effective communication by providing a mechanism that allows the source and destination to establish the timing of transmission and receipt of data.

TCP/IP Encapsulation

• A device encrypts data via these layers: Transport layer sends segments to the internet layer -> internet layer sends packets to network access layer -> network access layer creates frames to release bits to network media

TCP/IP Application Layer Protocols

• DNS, DHCP, and FTP are part of the TCP/IP protocol suite.

Key Networking Organizations

• The ISOC fosters the open development, evolution, and use of the Internet.
• The ISO is the largest developer of international standards.

Transport Layer PDU

• The transport layer PDU is referred to as a segment.

IPv4 Configuration Elements

• Configuring IPv4 requires an IP address for identification and a subnet mask, and default gateway to commmunicate to other networks

Encapsulation

• Encapsulation occurs when one PDU is placed inside another PDU to carry data from one protocol in another protocol data unit

TCP/IP Model Layer Function

• The internet layer in the TCP/IP model handles message routing through an internetwork.

TCP/IP Protocol Order of Events

• The Telnet-formatted data is provided to the next layer first, followed by the TCP header, the IP header, and then the Ethernet header.

Network Interface Card (NIC)

• When bits are received from the network medium, the NIC of a host uses the frame PDU format.

Addressing

• When ServerB attempts to contact HostA, ServerB will generate frame with MAC address of RouterB, as well as a packet with destination IP of HostA

Response Timeout

• Response timeout helps a computer react accordingly if a server does not immediately respond to a data request.

Decoding received transmissions from web server

• When a web client receives a response from a web server, the correct order of the protocol stack used to decode the transmission is: Ethernet, IP, TCP, HTTP

OSI and TCP/IP Model

• The TCP/IP network access layer combines the functionalities of the OSI data link and physical layers.

OSI (Logical Addressing)

• Logical addressing is added during encapsulation at the network layer.

Multicast Messages

• Addresses a select group of hosts.

Network Protocol Function

• Network protocols define how messages are exchanged between source and destination.

Networking Devices using Open Standard Protocols

• Devices using open standard protocols allow successful exchange of data from clients and servers using a different operating system.

Router and Network traffic

• The router is the device determines the correct path for messages within interconnected networks.

SVI Swith0 IP Adress activity

• By using the command show running configuration or show ip interfaces brief it can be determined that SVI Switch0 IP adress is 192.168.5.10

Layer 2 Switch IP Address Requirement

• Layer 2 switches needs an IP address to be managed remotely.

Router Configuration Error

• "Invalid input detected at marker." indicates the command was not entered in privileged EXEC mode due to the > symbol.

Safe/Secure Network Access

• Only the extranet describes a network owned by one organization that provides safe and secure access to individuals working for a different organization

Data Storage

• Storing personal files on servers over the internet to proved access to cloud, cloud provide access anywhere, anytime and on device

Network Type

• peer-to-peer, describes one computer being both client and server

Network Type

• SOHO (Small Office/Home Office) is a type of network people can use at home or in a small office with remote connection

Data Access

• the client/server model is where dedicated computers run server software

Network Descriptions

• powerline networking describes device connection to LAN with an electrical outlet
• quality of service (QoS) defines a network policy for priority given to voice and video data flow
• intranet belongs to an organizations private collection of LANs and WANs
• BYOD, is when a networks allows devices across a business or campus network

Network Data Access

• network layer is used to added source IP adress during, the encapsulation process
• transport layer is used to add destination port number, during, the encapsulation process
• application layer adds data during the encapsulation process
• network layer is used to add source IP address during the encapsulation process
• network layer is used to add a destination IP address during encapsulation
• data link layer is used to add the source MAC address

Network devices

• Transport layer is used to add source/destination port, transport layer, application layer
• data link layer is used to add source/destination MAC address
• frame describes when the network medium gets bits by a host NIC
• A host is name for all computers connected to a network that participate directly in network communication
• Routers and switches are intermediary devices

Network Cable Usage

• Fiber optic cables are used to transmit data that is encoded in pulses of light.

Intermediary Devices

• Routers and switches are intermediary devices.

Damaged Network/Fault Tolerance

• fault tolerance is a the characteristic of a network for quick response to power failure of network devices

OSI Physical

• OSI physical layer transmits bits across the local media
• full-duplex connectivity is why two strands of fiber used for a single connection
• transmitfull-duplex connectivityted messages being distorted from signals in adjacent wires is crosstalk
• twisting circuit wire pairs together, reduces the effect of copper cables in crosstalk

Wireless

• backbone cabling in an enterprise, requires Fiber optics
• Long-haul networks, require Fiber optics
• guest access in a coffee shop, requires wireless
• Bluetooth devices and microwaves cause wireless networks to affect wireless networks (microwaves and cordless phones)

Ethernet

• It is least affected by EMI or RFI
• It has loss of signal strength as distance increases.

Data/Ethernet

• data link packages various Layer 3 PDUs into a frame format that is compatible with the network interface
• verify the integrity of the received frame, is when a CRC value found in FCS field of a frame

Encapsulation

• In ethernet the physical addresses is added
• the data link contains the area described as error detection the frame header consist with layer type a partial mesh topology is comparing connects high availability with remote sites switchs can examine to determine receive frame with frame check sequence
• The magnetic field around the adjacent pairs of wire can causes crosstalk within the cable pairs
• UTP can be used to determine network cabling

Interference

• crosstalk and electromagnetic interference are two factors cause cables to interfere

Data Link Layer

• Data packages various PDUs
• Data Integrity of the received frame can be compared to CRC value

Subplayers/Subcategories

• auto media configuration is an example of auto-MDIX feature
• switch devices connect to a central devices, creates, more new central intermediate devices in an extends topology
• logical address is is an ID required to know as LLC sublayer

802.11

• Ethernet typically consist with CSMA/CD and CSMA/CA is used by IEEE

Ethernet Communication Process/Features

• physical address is use ethernet, when adding an Ethernet network
• The Ethernet header and trailer contains item.
• all network devices must listen before transmitting

Auto-MDIX Switch (Layer 2 Data Switching)

• enable a switch to use a crossover or a straight-through Ethernet

Data communication

• After Layer 2 switch is use to switch incoming and outgoing frames for support, using a shared memory buffering will perform best for this task

Frames Transmitting

• The final transmitted message between data will hold 00-60-2F-3A-07-CC with frames are transiting from between two data point

Switching Methods Transmitting/Receiving

• Store-and-forward and Error Checking
• Store-and forway method, also provides frame error checking and detection
• To use a cut-though swithcing it will generate the low levels of latency
• To know whats the correct result of to connect to the new cables
• When a frame doesn't support in the switch that the the switch doesn't know what the value is
• Store-and-forward uses used the cyclic redundancy check to determine if the frame has been modified during transit

Auto MDIX

Allows connections to configurable network

Important actions between switches

• Switch1 has to be in the in the router to move to priveiledged EXEC mode
• Switches will have to know the source MAC addresses to know what is built is built and maintained for MAC addresses tale entries

Types of Communication

• The logical link control will create a communication in software
• The data link player, the user have LLC communicate to help with more upper level communications

Wireless Connections

• To properly maintain to have to check to make sure that each untransisted wire not to over lap and is all the way to the bare wires
• You will have to use straight through for both and they are switches and a port

Port activity and Operational

• They way to determinates if port activity is show ip information

Attenuation Properties

• Etherner Loss Signal

Copper Interference

• greater distance run per cable and limited suceptibility to EMI/RFI

OSI Models

• Modulation is how the proccess by which one wave is modified by another wave
• Bandwidth, what media can carry
• goodput is describe what amount of data transferred over period of time
• Throughput means The transfer of bits in a medium
• Latency is how for data/delay of travelling from one point of to another point
• Electrical pulses and coppercables
• light uses fiber optics
• air uses microwave

Medium Accesss control

• Controls the responsible sending/receiving is what the NIC it

What to do to transfer/travel

• Encapuslating
• What contains to data linker is the LLC which, helps with network help identify with frame network

What will the router do?

• It will create a new layer for Ethernet to be sent to the destination for new processes
• The default gateway address is used to forward packets originating from the switch to remote networks
• Connectionless: It does not provide error control to receiving and transporting end to end delivery and must help rely to the upper layer to solve this problem

Layer 2 Data

• Create a new address to deliver/deliver an packet to a specific source
• The two main services for OSI are to create to a new data to deliver and have packt transfer
• Router = next path to see another connection
• If you get that a host is incorrectly set what will happen what will happened is that you know be able to connect with them

Wireless Interference

• Large network cause the the host Mac to be able to help

Command Lines

• the prompt with, enable can help with more connections
• the correct way to determine console to be used and is mostly the secure way to enter with encypts and SSH and is a strong password with authentication
• In order to verify if router is in three step you must complete (Phase 1, then Phase, then 2),
• With global command you can the IP
• Check what types of function on different port in a show IPS commands are the way for the network work

Access

• Exit Privillege mode to check code
• Show Command
• Copy run then startup after checking the data, then to make the new connection
• Use the banner to show what is the command to to config
• SSH and telnet are both remote access methods, then telnet then a is a to show a the secure way to use and SSH, and require
• **line console 0
• Show running commands are what that is show with the device function are
• Console: To check show connections the Aux Cable which has a port to connect all three

OSI models

• It gives the logical the data are not physical They will need to maintain to be connected to network
• When to sent to and use MAC address
• The router will not forward to the path with it has lost with a connection to the right
• A static entry needs to be set

What are the commands

• ARP -D can help clear the arp table to be able to get new functions, when you are having problems with it.
• They way for switches the host/and router can determine if is with a arp to know where they have

Packets

• Packets has the broadcasts to let each destination as and it must come from all ports
• The two data are the best to choose they destination and if what is in the data if has a lot
• You can with the a new connection

The correct address?

• MAC is never sent has or and is not in the best
• It provides the the type and the address to see if where is

IP

• To show the TCP, IPS and has to be with the top with

Connections

• You will to make sure they connect and have to make sure data the is
• What properties is to use if connected and is not in service they are what is used for fix the ARp
• With static we are to give help with all connections What to do If your destination is not connected, to the right path
• You always can clear the ARP is something goes wrong you always should know how to with in case
• And also do the the connection that you can use and put the main and then to show the other information in cases.