IP V4 protocol
Internet Protocol Version 4 (IPv4) is the fourth revision of the IP and a widely used protocol in data communication over different kinds of networks. IPv4 is a connectionless protocol used in packet-switched layer networks, such as Ethernet. It provides the logical connection between network devices by providing identification for each device. There are many ways to configure IPv4 with all kinds of devices - including manual and automatic configurations - depending on the network type. IPv4 is based on the best-effort model. This model guarantees neither delivery nor avoidance of duplicate delivery; these aspects are handled by the upper layer transport.A communication protocol is a system of digital rules for data exchange within or between computers.
Protocol layering now forms the basis of protocol design. It allows the decomposition of single, complex protocols into simpler, cooperating protocols, but it is also a functional decomposition, because each protocol belongs to a functional class, called a protocol layer. The protocol layers each solve a distinct class of communication problems.
A Connectionless packet delivery (or packet-switched) system (or service) is offered by the Internet, because it adapts well to different hardware, including best-effort delivery mechanisms like the ethernet. Connectionless delivery means that the messages or streams are divided into pieces that are multiplexed separately on the high speed intermachine connections allowing the connections to be used concurrently. Each piece carries information identifying the destination.
ISO/OSI model
The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnectionproject at the International Organization for Standardization (ISO).The model groups communication functions into seven logical layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer.
IP packet parameters
Internet Protocol being a layer-3 protocol (OSI) takes data Segments from layer-4 (Transport) and divides it into packets. IP packet encapsulates data unit received from above layer and add to its own header information.
- Version: Version no. of Internet Protocol used (e.g. IPv4).
- IHL: Internet Header Length; Length of entire IP header.
- DSCP: Differentiated Services Code Point; this is Type of Service.
- ECN: Explicit Congestion Notification; It carries information about the congestion seen in the route.
- Total Length: Length of entire IP Packet (including IP header and IP Payload).
- Identification: If IP packet is fragmented during the transmission, all the fragments contain same identification number. to identify original IP packet they belong to.
- Flags: As required by the network resources, if IP Packet is too large to handle, these "flags" tells if they can be fragmented or not. In this 3-bit flag, the MSB is always set to "0".
- Fragment Offset: This offset tells the exact position of the fragment in the original IP Packet.
- Time to Live: To avoid looping in the network, every packet is sent with some TTL value set, which tells the network how many routers (hops) this packet can cross. At each hop, its value is decremented by one and when the value reaches zero, the packet is discarded.
- Protocol: Tells the Network layer at the destination host, to which Protocol this packet belongs to, i.e. the next level Protocol. For example protocol number of ICMP is 1, TCP is 6 and UDP is 17.
- Header Checksum: This field is used to keep checksum value of entire header which is then used to check if the packet is received error-free.
- Source Address: 32-bit address of the Sender (or source) of the packet.
- Destination Address: 32-bit address of the Receiver (or destination) of the packet.
- Options: This is optional field, which is used if the value of IHL is greater than 5. These options may contain values for options such as Security, Record Route, Time Stamp, etc.
ICMP protocol
The Internet Control Message Protocol (ICMP) is one of the main protocols of the Internet Protocol Suite. It is used by network devices, like routers, to send error messages indicating, for example, that a requested service is not available or that a host or router could not be reached.ICMP messages are sent in several situations: for example, when a datagram cannot reach its destination, when the gateway does not have the buffering capacity to forward a datagram, and when the gateway can direct the host to send traffic on a shorter route. The Internet Protocol is not designed to be absolutely reliable. The purpose of these control messages is to provide feedback about problems in the communication environment, not to make IP reliable. There are still no guarantees that a datagram will be delivered or a control message will be returned. Some datagrams may still be undelivered without any report of their loss. The ICMP messages typically report errors in the processing of datagrams. To avoid the infinite regress of messages about messages etc., no ICMP messages are sent about ICMP messages.
IP address
All IP addresses are made up of four parts (quadrants) separated by dots, like this: XXX.XXX.XXX.XXX, where each XXX can be any number between 0 and 255. If you know binary, you will understand that each of these numbers are stored in 8 bits (binary digits), and the number of possibilities you can have is 2 raised to the power of 8, which is 256 (0-255).An IP address consists of two parts: the network part and the machine part. Let us make an analogy to your house's address. It is made up of the country part, then the city part, then the street part. All people living in your locality will have the same country and city parts in their addresses. Only the house number and street parts will be different.
For IP, all machines on a same network will have the same left (network) part. The right side varies based on machines. For example, right now, I am writing this within a LAN. The LAN router's IP address is 10.15.30.1; my machine's IP address is 10.15.30.5 and my fellow LAN-mate's IP address is 10.15.30.6. In this LAN, the network part is 10.15.30 and the machine part is the last quadrant. We can have a maximum of 256 machines on our LAN. Bigger networks have smaller network parts and bigger machine part, so as to accommodate more machines on the network.
Network subnets
A subnetwork, or subnet, is a logical, visible subdivision of an IP network. The practice of dividing a network into two or more networks is called subnetting.Computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address. This results in the logical division of an IP address into two fields, a network or routing prefix and the rest field or host identifier. The rest field is an identifier for a specific host or network interface.
An IP address consists of a host and a network portion. Coupled with a subnet mask, you can determine which part is the subnet, how large the network is, and where the network begins. Operating systems need to know this information in order to determine what IP addresses are on the local subnet and which addresses belong to the outside world and require a router to reach. Neighbouring routers also need to know how large the subnet is, so they can send only applicable traffic that direction. Divisions between host and network portions of an address are completely determined by the subnet mask.
Network classes
Network addressing architecture divides the address space for Internet Protocol Version 4 (IPv4) into five address classes. Each class, coded in the first four bits of the address, defines either a different network size, i.e. number of hosts for unicast addresses (classes A, B, C), or multicast network (class D). The fifth class (E) address range is reserved for future or experimental purposes. Knowing network classes becomes an issue when you deal with routing.Network mask
The routing prefix of an address is written in a form identical to that of the address itself. This is called the network mask, or subnet mask, of the address. For example, a specification of the most-significant 18 bits of an IPv4 address, 11111111.11111111.11000000.00000000, is written as 255.255.192.0. If this mask designates a subnet within a larger network, it is also called the subnet mask. This form of denoting the network mask, however, is only used for IPv4 networks.Routing table
A routing table is a set of rules, often viewed in table format, that is used to determine where data packets travelling over an Internet Protocol (IP) network will be directed. All IP-enabled devices, including routers and switches, use routing tables.A routing table contains the information necessary to forward a packet along the best path toward its destination. Each packet contains information about its origin and destination. When a packet is received, a network device examines the packet and matches it to the routing table entry providing the best match for its destination. The table then provides the device with instructions for sending the packet to the next hopon its route across the network.
Default gateway
The default gateway is the device, usually a router, that passes network data from the local network (the devices at your home or business) to other networks (like the Internet). In most cases in basic networks, the important part of the default gateway is the IP address that is assigned to that device - again, usually a router. This IP address is often referred to as the gateway IP.Lookup
Every machine that is on a TCP/IP network ( a local network, or the Internet ) has a unique Internet Protocol ( IP ) address. IP-Lookup helps you to find information about your current IP address or any other IP address. It supports both IPv4 and IPv6addresses. Using an IP lookup service you can find the whereabouts of a computer or router, the owner and the name of the computer.For example, you can use IP Address Lookup to make sure an individual is located where they say they are in order to avoid fraud.
It is sometimes useful to know whether somebody is contacting you from the USA, the UK, Nigeria or China for example.
Broadcast
In telecommunication and information theory, broadcasting refers to a method of transferring a message to all recipients simultaneously. Broadcasting can be performed as a high level operation in a program, for example broadcasting Message Passing Interface, or it may be a low level networking operation, for example broadcasting on Ethernet.
Subnet address
Subnetting enables the network administrator to further divide the host part of the address into two or more subnets. In this case, a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format.The full address is: 10010110.11010111.00010001.00001001
The Class B network part is: 10010110.11010111
and the host address is: 00010001.00001001
If this network is divided into 14 subnets, however, then the first 4 bits of the host address (0001) are reserved for identifying the subnet.
The subnet mask is the network address plus the bits reserved for identifying the subnetwork -- by convention, the bits for the network address are all set to 1, though it would also work if the bits were set exactly as in the network address. In this case, therefore, the subnet mask would be 11111111.11111111.11110000.00000000. It's called a mask because it can be used to identify the subnet to which an IP address belongs by performing a bitwise AND operation on the mask and the IP address. The result is the subnetwork address:
Subnet Mask 255.255.240.000 11111111.11111111.11110000.00000000
IP Address 150.215.017.009 10010110.11010111.00010001.00001001
Subnet Address 150.215.016.000 10010110.11010111.00010000.00000000
Private network address
Private networks can use IP addresses anywhere in the following ranges:- 192.168.0.0 - 192.168.255.255 (65,536 IP addresses)
- 172.16.0.0 - 172.31.255.255 (1,048,576 IP addresses)
- 10.0.0.0 - 10.255.255.255 (16,777,216 IP addresses)
Why is that? Because in a private network, the router connects to the Internet. From there, the router connects the other devices (usually desktops, laptops and tablets).
Because the private address ranges in a network don't have to be synchronized with the rest of the world, the complete address range is available from any network. A network administrator using these private addresses has more room for subnetting, and many more assignable addresses.
These blocks of addresses can be used by anyone, anywhere. Even if your neighbour is using the exact same addresses, it won't cause a problem. This is possible because these addresses are known as non-routable addresses. The network devices on the Internet are programmed to recognize these addresses. These devices (known as routers) will recognize that these are private addresses belonging to your network and will never forward your traffic onto the Internet.
You do need to obtain one real address from the general pool so that your home router can perform what is known as Network Address Translation (NAT). NAT is a process in which your router changes your private IP Address into a public one so that it can send your traffic over the Internet, keeping track of the changes in the process. When the information comes back to your router, it reverses the change (from a real IP address into a private one) and forwards the traffic back to your computer.
Network address translation
Network address translation (NAT) is a methodology of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device. The technique was originally used for ease of rerouting traffic in IP networks without renumbering every host. It has become a popular and essential tool in conserving global address space allocations in face of IPv4 address exhaustion.- Static NAT - Mapping an unregistered IP address to a registered IP address on a one-to-one basis. Particularly useful when a device needs to be accessible from outside the network.
- Dynamic NAT - Maps an unregistered IP address to a registered IP address from a group of registered IP addresses
- Overloading - A form of dynamic NAT that maps multiple unregistered IP addresses to a single registered IP address by using different ports. This is known also as PAT (Port Address Translation), single address NAT or port-level multiplexed NAT.
- Overlapping - When the IP addresses used on your internal network are registered IP addresses in use on another network, the router must maintain a lookup table of these addresses so that it can intercept them and replace them with registered unique IP addresses. It is important to note that the NAT router must translate the "internal" addresses to registered unique addresses as well as translate the "external" registered addresses to addresses that are unique to the private network. This can be done either through static NAT or by using DNS and implementing dynamic NAT.
RIPE
Reseaux IP Europeens (RIPE, French for "European IP Networks") is a forum open to all parties with an interest in the technical development of the Internet. The RIPE community’s objective is to ensure that the administrative and technical coordination necessary to maintain and develop the Internet continues. It is not a standards body like the Internet Engineering Task Force (IETF) and does not deal with domain names like ICANN.RIPE is not a legal entity and has no formal membership. This means that anybody who is interested in the work of RIPE can participate through mailing lists and by attending meetings. RIPE has a chairman to keep an eye on work between RIPE meetings and to be its external liaison. Rob Blokzijl was the spokesperson at the start and later the chairman. The RIPE community interacts via RIPE Mailing Lists, RIPE Working Groups, and RIPE Meetings.
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN /'a?kan/ EYE-kan) is a nonprofit organization that is responsible for the coordination of maintenance and methodology of several databases of unique identifiers related to the namespaces of the Internet, and ensuring the network's stable and secure operation.Most visibly, much of its work has concerned the Internet's global Domain Name System, including policy development for internationalization of the DNS system, introduction of new generic top-level domains (TLDs), and the operation of root name servers. The numbering facilities ICANN manages include the Internet Protocoladdress spaces for IPv4 and IPv6, and assignment of address blocks to regional Internet registries. ICANN also maintains registries of Internet protocol identifiers.
Physical layer
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first (lowest) layer. The implementation of this layer is often termed PHY.The physical layer consists of the basic networking hardware transmission technologies of a network. It is a fundamental layer underlying the logical data structures of the higher level functions in a network. Due to the plethora of available hardware technologies with widely varying characteristics, this is perhaps the most complex layer in the OSI architecture.
The physical layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. The bit stream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a hardware transmission medium. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, themodulation scheme to use and similar low-level parameters, are specified here.
Within the semantics of the OSI network architecture, the physical layer translates logical communications requests from the data link layer into hardware-specific operations to effect transmission or reception of electronic signals.
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