Physical topology / Logical topology
- indicates arrangement of different elements of network
- reflect physical layout of devices and cables to a form a connected network
- refers to the abstract representaion of how data flows and is transmitted within a network (independent of its physical layout)
- how softeare controls access to network resources
- how specific resources are sared to the network
Network Operating System(also called a server operating system)
a software that connects multiple devices and computers on the network and allows them to share resources on the network
- highly stable due to central server
- provide good security
- upgration of new technology and hardware can be easily implementd
-provide remote access to servers from different location
- printers and application sharing on the network
- file system and database sharing
- provide good sercurity by using functionality like user authentication and access control
- create backuos of data
- inter-networking
-creating and managing user accounts on the network
- contorolling access to resources on the network
- provide communication services between the device on the network
- monitor and troubleshoot the network
- configuring and managing the resources on the network
peer-to-peer network model / client-serve netowrk model
- simple to configure
- less expensive to set up and mantain than other types of network
- not scalable
- unsecure
- no centrally backup for files and folders
the OS(operating system) of each computer on the network is responsible for controling access its resources without centralized control, which means no computer has more authority than another; each computer controls its own resources and communicates directly with other computers
resources are managed by the NOS via a centralized directory database.
Active Directory
The centralized directory database that contains user account information and security for the entire group of computers on a network.
Active Directory Domain Service
The Active Directory service that manages the process allowing a user to sign on to a network from any computer on the network and get access to the resources that Active Directory manages.
- user accounts and passwords to the network are assigned in one place
- access to multiple shared resources can be centrally granted to a single user or groups of users
- problem on the network can be monitored, diagnosed, and often fixed from one location
- it's easier to add users and devices to a client-server network
A resource the network makes available to its users, including applications and the data provided by these applications.
Data or a service requested by one computer from another.
HTTP, SSL, TLS and HTTPS
HTTP (Hypertext Transfer Protocol) is layered on top of an encryption protocol, such as SSL(Secure Sockets Layer) or TLS(Transport Layer Security), the result is HTTPS(HTTP Secure)
SMTP, POP3, IMAP4
the client uses SMTP(Simple Mail Transfer Protocol) to send an email message to the first server, then the recipients mail server delivers the message to the receiving client using POP3(Post Office Protocol, ver3) or IMAP4(Internet Message Access Protocol)
Network Interface Card
The component in a computer or other networking device that enables the device to connect to the network and communicate with other devices. Also called network adapters.
a star topology, a bus topology, a hybrid topology, hub-and-spoke topology and a ring topology
A network layer device that uses logical addressing information to direct data between two or more networks and can help find the best path for traffic to get from one network to another.
MAN (metropolitan area network)
A network of connected LANs within a limited geographical area, such as multiple city government buildings around a city’s center.
WAN (wide area network)
A network that spans a long distance and connects two or more LANs.
7. Applicatoin layer
6. Presentation layer
5. SEssion layer
4. Transport layer
3. Network layer
2. Data link layer
1. Physical layer
entrance facility
the location where an incoming network service to make the transmission from WAN or MAN which are managed by ISP to LAN or CAN which are managed by the customer.
the device that marks where an ISP’s network ends and the organization’s network begins
Main Distribution Frame
the centralized point of interconnection between an organization’s LAN or WAN and a service provider’s network.
Also known as the ER(equipment room)
an enclosed space that holds network equipment. These spaces might have requirements for size, clearance around equipment, wall materials, and physical security (such as a locked door)
A wall- or rack-mounted panel where cables converge in one location.
the use of any network (either public or private) to carry voice signals using TCP/IP protocols.
- converts signals from a campus's analog phone equipment into IP data that can travel over the Internet
- converts VoIP data from an internal IP network to travel over a phone company's analog telephone lines.
SIP(Session Initial Protocol)
VoIP phone
Intermediate Distribution Frame
a junction that provides an intermediate connection between the MDF and end-user equipment on each floor and in each building.(there can be many IDFs connecting internal portions of the network)
The ANSI/TIA standards specify at least one IDF per floor, although large organizations may have several data rooms or closets per floor to better manage the data feed from the main data facilities.
Height - Rack height is measured in rack units (RU or U) with the industry standard being 42U tall—about 6 feet. Half-racks are usually 18U–22U tall.
Width - Equipment racks come in a standard 19-inch frame, meaning that the front is 19 inches wide. You might also come across 23-inch racks.
Depth - Rack depths vary considerably between manufacturers.
to prevent airflow blockages and heat buildup.
In a typical rack system, airflow through the chassis is designed to move from front to back. In data centers containing multiple rows of racks, a hot aisle/cold aisle layout pulls cool air from vents in the floor or from nearby, low-lying wall vents into the rows of racks. The hot air aisles are used to direct the heated air away from the racks into exhaust vents for cooling.
100m
90m to connect the network device in the data room to a data jack on the wall in the work area.
10m(maximum) to connect the wal jack to a workstation.
crosstalk
that is possibility of transmission interference between wires, a phenomenon
the radius of the maximum arc into which you can loop a cable without impairing data transmission.
to prevent you from later having to track down errors in mutiple, long stretches of cable
(Continuity)
this will leads to difficult-to-diagnose data error.
to prevent damaging from rolling chairs or foot traffic
to reduce the risk of damnage from pests or water
Electromagnetic Interference
A type of interference that can be caused by motors, power lines, televisions, copiers, fluorescent lights, or other sources of electrical activity.
to reduce the possibility of noise(interference) that can affect your network's signals
Network Mapper is a scannning tool
to assess large networks quickly and provide comprehensive, customized information about a network and its hosts.
Nmap / Zenmap / Cisco
• reuirements analysis
Identify network requirements and business needs.
• design planning
Progress from big picture goals to detailed decisions.
• development and testing
Purchase equipment and test before deploying.
• implementation
Deploy new equipment to replace old equipment, and continue testing to achieve a new, stable baseline.
• documentation and maintenance
Apply effective monitoring techniques to detect and address problems, and keep documentation updated.
•. evaluation
As improvements are needed or devices break down, perform a cost–benefit analysis to identify devices reaching the end of their life cycle and determine whether to discard, replace, or upgrade.
RFP(request for proposal)
MOU(memorandum of understanding)
MSA(master service agreement)
SOW(statement of work)
SLA(service-level agreement)
MLA(master license agreement)
A document requesting that vendors submit a proposal for a product or service that a company wants to purchase.
A document presenting the intentions of two or more parties to enter into a binding agreement, or contract. usually not a legally binding document.
A contract that defines terms of future contracts.
defines the level of service expected by a customer from a supplier
a legal contract between the City of Vacaville and a wireless carrier (also known as a wireless provider), which identifies the City as the licensor and the wireless carrier as the licensee.
layer 2, Data link layer
layer 3, Network layer
Routers, which function primarily at layer 3, check IP addresses to determine which network a message is destined for.
a number used by the transport layer to find an application.
It identifies one application among several that might be running on a host.
Fully Qualified Domain Name
A host name plus domain name that uniquely identifies a computer or location on a network.
The last two parts of an FQDN, such as mycompany.com. Usually, a domain name is associated with the company’s name and its type of organization, such as a school or nonprofit organization.
identifies the individual computer on the network.
Ftp - given to an FTP server
www - often the host name assigned to a computer running a web server.
Internet Corporation for Assigned Names and Number
a nonprofit organization charged with setting many policies that guid how the internet works
maintain and assign IP address
OUI(Organaizationally Unique Identifier)
identifies the NIC's manufacturer
the extension identifier or device ID and identify the device itself.
Manufactures assign each NIC a unique extension identifier, based on the NIC's model and manufacture date.
to identify devices on the local are network(LAN)
As each device communicates on the network, the switch identifies the sending device’s MAC address from its transmitted message.
The MAC address is stored in a MAC address table that maps each MAC address to a physical port on the switch.
ipconfig /all
An IP address that is manually assigned to a device and remains constant until it is manually changed.
An IP address that is assigned to a device upon request and may change when the DHCP lease expires or is terminated.
the dynamic distribution of IP addresses to devices on a network.
helps determine which part of an IP address identifies the network and which part identifies the host within that network.
a computer can determine if another computer with a given IP address is on its own or a different network.
a computer, router, firewall, or other device that a host uses to access another network.
The gateway device that nodes on the network turn to for access to the outside world.
- provides a connection to all resources outside the local network when static routes aren’t available (which is most of the time).
class A - 1.x.y.z ~ 126.x.y.z, the first 8 bits for network information.
class B - 128.0.y.z ~ 191.255.y.z, the first 16 bits for the network information.
class C - 192.0.0.z ~ 223.255.255.z, the first 24 bits for the network information.
the rest of bits other than the network information are used to identify hosts.
class D - 224.x.y.z ~ 239.x.y.z, used for multicast transmissions
class E - 240.x.y.z ~ 254.x.y.z, not available for general use
public IP address
an IP adderess that is valid for use on public networks, such as the Internet.
IP addresses that can be used on a private network but not on the Internet.
IEEE recommends the following IP address ranges for private use:
class A - 10.0.0.0 through 10.255.255.255;
class B - 172.16.0.0 through 172.31.255.255;
class C - 192.168.0.0 through 192.168.255.255.
static IP address - manually assigned by the network administrato
dynamic IP address - automatically assigned by a DHCP server each time a computer connects to the network.
Network Address Translation
When private devices need access to other networks or the Internet, a public-facing gateway (such as a router or firewall) substitutes the private IP addresses used by computers on the private network with its own public IP address.
Network address translation
good for security; the gateway hides the private network’s hosts behind this one address.
Port Address Translation
- assigns a separate TCP port to each session between a local host and an Internet host
ex) When the Internet host responds to the local host, the gateway uses PAT to determine which local host is the intended recipient.
help facilitate communication between devices by ensuring that data reaches the correct application or service on the destination device.
Small home networks with only a single public IP address provided by its ISP use SNAT thatthe gateway assigns the same public IP address to a host each time it makes a request to access the Internet.
Private network (private IP address) -> router using NAT -> uses SNAT -> public IP address -> internet
the destination IP address is changed to the private IP address of the host inside the network when a message sent to the public IP address reaches the router managing DNAT.
Internet (public IP address) -> router using NAT -> uses DNAT -> private IP address
DNAT for incoming messages
2001::B80:0000:0000:D3:9C5A:00CC
or
2001:0000:B80::0000:D3:9C5A:00CC(recommended)
- only one block of 0000 can be ::
- leading zeroes in a four-character hex block can be eliminated
When a network is configured to use both IPv4 and IPv6 protocols.
the interface and are called the interface ID or interface identifier.
Global address / link local address / loopback address
- can be routed on the internet(similar to public IPv4 address)
-most begin with the prefix 2000::/3
"/3" indicates that the first three bits are fixed and are always 001.
- can be used for communicationg with nodes in the same link
- begin with FE80::/10
- sometimes written as FE80::/64 that are not allowed past the local link or on the internet
the first 10 bits(indicated by /10) of the reseved prefix are fixed and remaining 54 bits in the 64-bit prefix are all zeroes
- can be used to test that an interface and supporting protocol stack are functioning properly
- ::1/128(consists of 127 zeros followed by a 1)
FC00::/7 (fist 7 bits are always 1111 110)
FD00::/8 (first 8 bits are always 1111 1101)
FF00::/8 (first 8 bits are always 1111 1111)
ipconfig
consists of both a host’s IP address and a process’s TCP or UDP port, with a colon separating the two values.
ex) the standard port for the Telnet service is TCP 23. If a host has an IP address of 10.43.3.87, the socket for Telnet running on that host is 10.43.3.87:23.
Well-known ports - range from 0~1023, used for Telnet, FTP and HTTP
Registered ports - range from 1024~49151, used temporarily by processes for nonstandard assignments to increase security
Dynamic and Private ports - range from 49152~65535, open for use without restriction
finds the internet protocol (IP) address or domain name system (DNS) record for a specific hostname
the diagnosis of a printer problem and recommended steps to fix the problem
A TCP/IP troubleshooting utility that can verify TCP/IP is installed, bound to the NIC, configured correctly, and communicating with the network. Ping uses ICMP (Internet Control Message Protocol) to send echo request and echo reply messages.
ICMP(INternet Control Message Protocol)
a lightweight protocol used to carry error messages and informaton about a network.
use the ping in command prompt.
"ping google.com"
Ping a host using its host name to verify you have Internet access and name resolution, and Google.com is a reliable site to use for testing.
Test for name resolution and display the host name to verify DNS is working.
ex) ping -a 8.8.8.8 will display Google's public DNS server
Use dig to query DNS nameservers for information about host addresses and other DNS records.
A utility available on Linux and macOS that provides more detailed domain information than nslookup.
A tool used to gather information about all devices connected to a network, including host names, manufacturer names, operating systems, IP addresses, MAC addresses, interfaces used, and open ports with running services.
IP scanner > Nmap, Zenmap and ipconfig
- Incorrect IP address
- Duplicate IP address
- Incorrect subnet mask
-Incorrect gateway
- Incorrect DNS or DNS issues
Name resolution issues
Pinging a host using its host name can verify you have Internet access and functioning name resolution (DNS) services because the host name must first be resolved before the host can be located and pinged.
layer 4, transport layer
layer 3, network layer
the header identifies the IP address of the destination host and the message is called a packet.
- connection-oriented (ensure the connection is established)
- sequencing and checksums (ensure the response)
- flow control (control speed, volume)
The TCP three-way handshake establishes a session before TCP transmits the actual data, such as an HTTP request for a web page.(transport layer right befor session layer, layer 5)
- connectionless protocol
-no connection is established by UDP before data is trasmitted
- provides no hadshake to establish a connection, acknowledgement of transmissions received, erro checking, sequencing, or flow control
- more efficient and faster than TCP
Layer 3, network layer
works in conjunction with IPv4 to discover the MAC address of a node on the local network and to maintain a database that maps local IPv4 addresses to MAC addresses.
Layer 2, Data link layer
displays and modifies the Internet-to-adapter address translation tables(lists devices with MAC address on the network) used by the Address in Networks and communication management.
- LLC(logical link control) sublayer
identifies the type of message and handle multiplexing, flow and error control, and reliability
- MAC sublayer
identifies the destination and source MAC addresses, provides the checksum in the frame's trailer
Ethernet
a header for TCP and UD at the transpor layer includes a port to identify the communicating aplication on the source host.
IP identifies the IP addres of the source host.
IPv4 address
ARP works in conjuction with IPv4 to discover the MAC address of a node on the local network and to maintain a database that maps local IPv4 addresses to MAC address.
IPsec (Internet Protocol Security)
SSL/TLS
SSL- Secure Sockets Layer
TLS- Transport layer Security
application layer, layer 7
transport layer, layer 4