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Networking Notes 2
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- 1What's Computer Networks and nodeIn the world of computing, a network is a collection of both hardware and software components (working together), that are able to communicate with one another
The term node is is used to generically identify a network-connected device
- A web server ... is a node
- An e-mail server ... is a node
- A database server ... is a node
- A personal desktop computer system ... is a node
- A network-connected printer ... is a node
- Notebook computer systems, smartphones, and tablets ... are nodes
- etc.
Nodes can be physically connected to a network (using a cable), or wirelessly connected (without a cable) - 2Unique IdentificationEach node that is connected to a network, must be uniquely identified in some way ... or how would you be able to distinguish between them?
A unique Media Access Control (MAC) address is hard-coded into each network adapter. A MAC address is also known as a physical address
Each MAC address is a 12-digit hexadecimal value, and is typically documented using a delimiting character
Examples: 00-24-d6-a7-b4-3f (most common notation)
00:24:d6:a7:b4:3f
A single node may include one or more network adapters, and therefore, will have one or more MAC addresses associated with it - 3Node ConnectivityNodes on a network are connected together by way of one or more types of network devices: Switches, Wireless Access Points, and Routers
A network switch is a device which nodes physically plug into using a cable. Network switches can be wired together to create a larger network
Wireless access points are used to connect wireless-capable nodes, including smartphones and tablets
Routers are used to connect together multiple networks
A combination of multiple switches, wireless access points, and routers are connected together to create the networks we see at home and in work environments
The Internet is just a collection of all networks around the world which are joined together - 4Node Connectivity 2For home networks, the physical box that connects all your nodes to the Internet (e.g. Linksys, Cisco, Apple, etc.) most likely includes all (3) network device components
- It is a wireless access point for you to connect your wireless nodes
- It has a few ports on it to physically connect your wired nodes ... and
therefore is a network switch
- It forwards data communications in-and-out to the Internet ... and
therefore is a router - 5The Internet Protocol (IP)A communication protocol is a set of rules which govern how nodes talk to one another on a network
Think of a communication protocol like a spoken language. Put two people in a room. One person speaks only English, and the second person speaks only French. Not a lot of communication from one person will be understood by the other person
The same can be applied to nodes on a network. All nodes must be capable of communicating using the same communication protocol, or no discernible information will be conveyed
The Internet Protocol (IP), is the most widely used communication protocol. Most nodes globally use the Internet Protocol to communicate in some way or another - 6The Internet Protocol (IP) 2IP is a routable protocol, providing a method of communicating between nodes located on a very small network, or nodes located on very large networks (including the Internet)
Router devices determine the pathway (a.k.a. the route) IP protocol communications take when nodes need to communicate with one another
IP provides logical address values that are then associated to MAC address values (creating a logical-to-physical relationship)
Communicating between multiple routed networks, using only MAC addresses, is not possible. MAC address awareness remains at a localized network level. MAC address lists are not propagated to other networks, (typically) beyond a router device. Each node maintains a list of recently communicated local nodes in an ARP table (ARP: Address Resolution Protocol). Nodes use the information in their ARP table to communicate with other nodes on the same localized network - 7IP, MAC, and Port NumbersIP addresses are used to locate a node’s network
Both IP addresses and MAC addresses, together, are used to locate a specific node on the network
Port numbers are used to identify which application or service is to be used to process the received data
All (3) items (IP address, MAC address, and port number), are required in order for one node to successfully communicate with another node on a network - 8The Internet Protocol (IP)Currently, there are (2) implemented versions of the Internet Protocol (IP):
- IPv4: Internet Protocol (version 4)
- IPv6: Internet Protocol (version 6) - 9IPv4 AddressesIPv4 addresses are (4) decimal delimited decimal values
Examples: 142.222.45.73
192.168.100.20
10.1.2.10
206.191.86.29
127.0.0.1
169.254.15.94
Range: 0.0.0.0 through 255.255.255.255
Limitation: Only (4.3 billion) unique logical addresses exist for IPv4. The
Internet has run out of IPv4 addresses - 10IPv6 AddressesIPv6 addresses are (8) colon delimited hexadecimal values
Examples: 2001:0da0:0023:0000:0000:d40e:0000:0064
2001:da0:23:0:0:d40e:0:64 (shortened)
2001:da0:23::d40e:0:64 (shortened again)
0:0:0:0:0:0:0:1
::1 (shortened)
Globally ... most networks currently utilize IPv4 as opposed to IPv6
Home networks, business networks, and the Internet are in a transition phase from IPv4 to IPv6. This is a very slow process (years), as:
- Most network administrators are reluctant to switch over to IPv6
- Many hardware products have not been updated to work with IPv6
- Many software products have not been updated to work with IPv6
If IPv6 were to completely replace IPv4, then the Internet would virtually never run out of IP addresses ever again - 11Multiple IP AddressesEach node’s network adapter can potentially have multiple IPv4 and/or IPv6 addresses associated with it
- 12IPv4 AddressingAn IPv4 address contains (2) pieces of information
- Network ID
- Node ID (a.k.a. Host ID)
The left-hand portion of an IPv4 address identifies the network ID, and identifies which local network the node is located on
The right-hand portion of an IPv4 address identifies the node ID, and identifies the specific node on the local network
Example (n = network ID; h = node ID):
10.0.1.200 (n.n.n.h)
10.0.1 - Is the network ID
200 - Is the node ID - 13Special Purpose IPv4 AddressLocal (Node) Loopback Address
Range: 127.0.0.0 - 127.255.255.255
Private Network Addresses
Range: 10.0.0.0 - 10.255.255.255
Private Network Addresses
Range: 172.16.0.0 - 172.31.255.255
Private Network Addresses
Range: 192.168.0.0 - 192.168.255.255
APIPA Addresses
Range: 169.254.0.0 - 169.254.255.255 - 14Local (Node) Loopback AddressThe local loopback address is a special purpose address which is used internally by the software running on a node
Any address beginning with (127) can be used by an IPv4 enabled node, however, it is almost always (127.0.0.1)
The local loopback address for a node with IPv6 enabled is (::1)
Every node that is IPv4 enabled has only (1) local loopback address associated with it (127.0.0.1)
Every node that is IPv6 enabled has only (1) local loopback address associated with it (::1)
Every node that is both IPV4 and IPv6 enabled, has (2) local loopback addresses associated with it (127.0.0.1 and ::1)
The local loopback address cannot be used to communicate between nodes on a network. It is used for local node purposes only - 15Private IPv4 Network AddressesRanges: 10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
Commonly found in home networks and business networks
IPv4 addresses in the above ranges are not routable on the Internet
Typically used to connect networks to the Internet by way of a NAT appliance (NAT: Network Address Translation)
A NAT appliance is a node which has at least (2) IP addresses associated with it. One IP address is accessible via the Internet, while the other IP address is not accessible via the Internet. The NAT appliance is responsible for taking IP traffic and forwarding it out to the Internet or forwarding it into the private network
Eliminates having to configure each node with an Internet routable IPv4 address - 16APIPA Special Purpose IPv4 AddressesRange: 169.254.0.0 - 169.254.255.255
APIPA: Automatic Private IP Addressing
Most nodes on a network, including the Internet, are configured to receive an IPv4 address automatically when it is powered on
Special nodes, called DHCP servers (DHCP: Dynamic Host Configuration Protocol), are responsible for issuing out IPv4 and/or IPv6 addresses to nodes located on the local network
If by chance a node does not receive an IPv4 address automatically from a DHCP server ... the node will configure itself with a randomly generated APIPA address. This will allow the node to communicate, but only on the local network, and only with other nodes configured in the same network range (169.254.h.h) - 17SubnetworksOriginally, IPv4 allowed for only (3) usable classes of networks
Class A
Range: 1.0.0.0 - 126.255.255.255 (n.h.h.h)
Number of Networks: 126
Number of Hosts (Nodes) per Network: 16,777,214
Class B
Range: 128.0.0.0 - 191.255.255.255 (n.n.h.h)
Number of Networks: 16,384
Number of Hosts (Nodes) per Network: 65,534
Class C
Range: 192.0.0.0 - 223.255.255.255 (n.n.n.h)
Number of Networks: 2,097,152
Number of Hosts (Nodes) per Network: 254 - 18SubnetworksThe original classes of networks were a very inefficient use of the available IPv4 addresses
In addition, the complete range of available IPv4 addresses included several “unused” or “reserved” addresses which could not be configured on nodes
Unused/Reserved
Ranges: 0.0.0.0 - 0.255.255.255
224.0.0.0 - 255.255.255.255 - 19Subnetworks 2Over time, and several advancements to the IPv4 standard, modern day IPv4 networks now allow network administrators to breakdown the network ID portion into smaller, more efficient mini-networks called subnets ... by using a technique called subnetting
Note: In this course, you will not be subnetting. You will be provided with IP address configuration details in the labs. Students enrolled in the Network Programs will be exposed to subnetting in future courses - 20Port NumbersFor each node’s IP address, there can be up to (65,536) unique port numbers
Range: 0 - 65,535
Port numbers are used by software applications and services to process the received data
Port numbers are associated with a unique IP address. Therefore, a node with multiple IP addresses can use the same port number for different applications or services ... as long as they are bound to a different IP address
Some common port numbers include:
80, 443 - Used for web browsing
25, 110, 143 - Used for sending and receiving e-mail messages - 21Port Numbers 2To connect to a node which includes (1) network adapter, and (3) unique IP addresses bound to it, there are potentially (196,608) unique possible ways to do so
1 x 3 x 65,536 = 196,608
To connect to a node which includes (3) network adapters, and (2) unique IP addresses bound to each, there are potentially (393,216) unique possible ways to do so
3 x 2 x 65,536 = 393,216
To connect to a node which includes (1) network adapter, and (200) unique IP addresses bound to it, there are potentially (13,107,200) unique possible ways to do so
1 x 200 x 65,536 = 13,107,200 - 22Port Numbers 3Port numbers are associated with software (applications or services) running on a node
Examples:
80 - Unsecured web browsing (http)
443 - Secured web browsing (https)
25 - Unsecured/secured sending of e-mail messages (smtp/smtp-s)
110 - Unsecured/secured receiving of e-mail messages (pop/pop-s)
143 - Unsecured/secured receiving of e-mail messages (imap/imap-s)
Where:
http(s) - Hypertext Transport Protocol (Secured)
smtp(-s) - Simple Mail Transport Protocol (Secured)
pop(-s) - Post Office Protocol (Secured)
imap(-s) - Internet Message Access Protocol (Secured)
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- Fichas sobre Networking Notes 2, creado por Sean nazaire el 25/09/2019.
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