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60-487: The Mobile IP allows for location-independent routing of IP datagrams on the Internet. Each mobile node is identified by its home address disregarding its current location in the Internet. While away from its home network, a mobile node is associated with a care-of address which identifies its current location and its home address is associated with the local endpoint of a tunnel to its home agent . Mobile IP specifies how

120-645: A de facto standard in the industry. In May 2005, the IETF defined a formal standard for it. An IP address conflict occurs when two devices on the same local physical or wireless network claim to have the same IP address. A second assignment of an address generally stops the IP functionality of one or both of the devices. Many modern operating systems notify the administrator of IP address conflicts. When IP addresses are assigned by multiple people and systems with differing methods, any of them may be at fault. If one of

180-408: A static IP address . In contrast, when a computer's IP address is assigned each time it restarts, this is known as using a dynamic IP address . Dynamic IP addresses are assigned by network using Dynamic Host Configuration Protocol (DHCP). DHCP is the most frequently used technology for assigning addresses. It avoids the administrative burden of assigning specific static addresses to each device on

240-401: A dynamically assigned IP address that seldom changes. IPv4 addresses, for example, are usually assigned with DHCP, and a DHCP service can use rules that maximize the chance of assigning the same address each time a client asks for an assignment. In IPv6, a prefix delegation can be handled similarly, to make changes as rare as feasible. In a typical home or small-office setup, a single router

300-531: A group of 8 bits (an octet ) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal , octal , or binary representations. In the early stages of development of the Internet Protocol, the network number was always the highest order octet (most significant eight bits). Because this method allowed for only 256 networks, it soon proved inadequate as additional networks developed that were independent of

360-456: A home network an unchanging address, it is more likely to be abused by customers who host websites from home, or by hackers who can try the same IP address over and over until they breach a network. Multiple client devices can appear to share an IP address, either because they are part of a shared web hosting service environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of

420-672: A large address space, there is no need to have complex address conservation methods as used in CIDR. All modern desktop and enterprise server operating systems include native support for IPv6 , but it is not yet widely deployed in other devices, such as residential networking routers, voice over IP (VoIP) and multimedia equipment, and some networking hardware . Just as IPv4 reserves addresses for private networks, blocks of addresses are set aside in IPv6. In IPv6, these are referred to as unique local addresses (ULAs). The routing prefix fc00:: / 7

480-489: A link. This feature is used in the lower layers of IPv6 network administration, such as for the Neighbor Discovery Protocol . Private and link-local address prefixes may not be routed on the public Internet. IP addresses are assigned to a host either dynamically as they join the network, or persistently by configuration of the host hardware or software. Persistent configuration is also known as using

540-449: A mobile host and a static host while reducing the effects of location changes while the mobile host is moving around, without having to change the underlying TCP/IP. To solve the problem, the RFC allows for a kind of proxy agent to act as a middle-man between a mobile host and a correspondent host. A mobile node has two addresses – a permanent home address and a care-of address (CoA), which

600-599: A mobile node registers with its home agent and how the home agent routes datagrams to the mobile node through the tunnel . In many applications (e.g., VPN , VoIP ), sudden changes in network connectivity and IP address can cause problems. Mobile IP was designed to support seamless and continuous Internet connectivity. Mobile IP is most often found in wired and wireless environments where users need to carry their mobile devices across multiple LAN subnets. Examples of use are in roaming between overlapping wireless systems, e.g., IP over DVB , WLAN , WiMAX and BWA . Mobile IP

660-420: A mobile node sends packets directly to the other communicating node, without sending the packets through the home agent, using its permanent home address as the source address for the IP packets. This is known as triangular routing or "route optimization" (RO) mode. If needed, the foreign agent could employ reverse tunneling by tunneling the mobile node's packets to the home agent, which in turn forwards them to

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720-493: A network in one transmission operation as an all-hosts broadcast . All receivers capture the network packet. The address 255.255.255.255 is used for network broadcast. In addition, a more limited directed broadcast uses the all-ones host address with the network prefix. For example, the destination address used for directed broadcast to devices on the network 192.0.2.0 / 24 is 192.0.2.255 . IPv6 does not implement broadcast addressing and replaces it with multicast to

780-410: A network, the network administrator assigns an IP address to each device. Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on network practices and software features. Some jurisdictions consider IP addresses to be personal data . An IP address serves two principal functions: it identifies the host, or more specifically, its network interface , and it provides

840-478: A network. It also allows devices to share the limited address space on a network if only some of them are online at a particular time. Typically, dynamic IP configuration is enabled by default in modern desktop operating systems. The address assigned with DHCP is associated with a lease and usually has an expiration period. If the lease is not renewed by the host before expiry, the address may be assigned to another device. Some DHCP implementations attempt to reassign

900-426: A part. RFC 2002 specified that MN use agent discovery to locate these entities. When connected to a foreign network, a MN has to determine the foreign agent care-of-address being offered by each foreign agent on the network. A node wanting to communicate with the mobile node uses the permanent home address of the mobile node as the destination address to send packets to. Because the home address logically belongs to

960-513: A single sender or a single receiver, and can be used for both sending and receiving. Usually, a unicast address is associated with a single device or host, but a device or host may have more than one unicast address. Sending the same data to multiple unicast addresses requires the sender to send all the data many times over, once for each recipient. Broadcasting is an addressing technique available in IPv4 to address data to all possible destinations on

1020-456: A valid IP address within the foreign network, so that it allows the mobile node to receive and make connections with any host in the outside. To send outgoing packets, the mobile node may as well use its home address but, since it is not a connected IP address for the current network attachment, some routers in the way might prevent the packets from reaching the destination. That is why, in IPv4 ,

1080-590: Is Network Mobility (NEMO) Network Mobility Basic Support Protocol by the IETF Network Mobility Working Group which supports mobility for entire Mobile Networks that move and to attach to different points in the Internet. The protocol is an extension of Mobile IPv6 and allows session continuity for every node in the Mobile Network as the network moves. Care-of address A care-of address (usually referred to as CoA )

1140-426: Is a built-in feature of IPv6. In IPv4, anycast addressing is implemented with Border Gateway Protocol using the shortest-path metric to choose destinations. Anycast methods are useful for global load balancing and are commonly used in distributed DNS systems. A host may use geolocation to deduce the geographic position of its communicating peer. This is typically done by retrieving geolocation info about

1200-400: Is a temporary IP address for a mobile device used in Internet routing. This allows a home agent to forward messages to the mobile device. A separate address is required because the IP address of the device that is used as host identification is topologically incorrect—it does not match the network of attachment. The care-of address splits the dual nature of an IP address, that is, its use

1260-588: Is associated with the network the mobile node is visiting. Two kinds of entities comprise a Mobile IP implementation: The so-called Care of Address is a termination point of a tunnel toward a MH, for datagrams forwarded to the MH while it is away from home. A Mobile Node (MN) is responsible for discovering whether it is connected to its home network or has moved to a foreign network. HA’s and FA’s broadcast their presence on each network to which they are attached. They are not solely responsible for discovery, they only play

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1320-435: Is defined for the special use of link-local addressing for IPv4 networks. In IPv6, every interface, whether using static or dynamic addresses, also receives a link-local address automatically in the block fe80:: / 10 . These addresses are only valid on the link, such as a local network segment or point-to-point connection, to which a host is connected. These addresses are not routable and, like private addresses, cannot be

1380-465: Is not required within cellular systems such as 3G, to provide transparency when Internet users migrate between cellular towers, since these systems provide their own data link layer handover and roaming mechanisms. However, it is often used in 3G systems to allow seamless IP mobility between different packet data serving node (PDSN) domains. The goal of IP Mobility is to maintain the TCP connection between

1440-416: Is recognized as consisting of two parts: the network prefix in the high-order bits and the remaining bits called the rest field , host identifier , or interface identifier (IPv6), used for host numbering within a network. The subnet mask or CIDR notation determines how the IP address is divided into network and host parts. The term subnet mask is only used within IPv4. Both IP versions however use

1500-421: Is reserved for this block, which is divided into two / 8 blocks with different implied policies. The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted. Early practices used a different block for this purpose ( fec0:: ), dubbed site-local addresses. However, the definition of what constituted a site remained unclear and

1560-662: Is the only device visible to an Internet service provider (ISP), and the ISP may try to provide a configuration that is as stable as feasible, i.e. sticky . On the local network of the home or business, a local DHCP server may be designed to provide sticky IPv4 configurations, and the ISP may provide a sticky IPv6 prefix delegation, giving clients the option to use sticky IPv6 addresses. Sticky should not be confused with static ; sticky configurations have no guarantee of stability, while static configurations are used indefinitely and only changed deliberately. Address block 169.254.0.0 / 16

1620-409: Is to identify the host and the location within the global IP network. The care-of address can be acquired by the mobile node in two different ways: Given the imminent IPv4 address exhaustion , the first solution is more frequently chosen, because it does not waste a public IP address for every mobile node when changing network location, as the collocated CoA does. The care-of address has to be

1680-477: The Point-to-Point Protocol . Computers and equipment used for the network infrastructure, such as routers and mail servers, are typically configured with static addressing. In the absence or failure of static or dynamic address configurations, an operating system may assign a link-local address to a host using stateless address autoconfiguration. Sticky is an informal term used to describe

1740-415: The CIDR concept and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix . For example, an IPv4 address and its subnet mask may be 192.0.2.1 and 255.255.255.0 , respectively. The CIDR notation for the same IP address and subnet is 192.0.2.1 / 24 , because the first 24 bits of the IP address indicate

1800-422: The IP address of the other node from a database. A public IP address is a globally routable unicast IP address, meaning that the address is not an address reserved for use in private networks , such as those reserved by RFC   1918 , or the various IPv6 address formats of local scope or site-local scope, for example for link-local addressing. Public IP addresses may be used for communication between hosts on

1860-597: The Internet today. The original version of the Internet Protocol that was first deployed in 1983 in the ARPANET , the predecessor of the Internet, is Internet Protocol version 4 (IPv4). By the early 1990s, the rapid exhaustion of IPv4 address space available for assignment to Internet service providers and end-user organizations prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand addressing capability on

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1920-468: The Internet, but it lacked scalability in the face of the rapid expansion of networking in the 1990s. The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrary-length prefixes. Today, remnants of classful network concepts function only in a limited scope as

1980-500: The Internet, such as factory machines that communicate only with each other via TCP/IP , need not have globally unique IP addresses. Today, such private networks are widely used and typically connect to the Internet with network address translation (NAT), when needed. Three non-overlapping ranges of IPv4 addresses for private networks are reserved. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry. Any user may use any of

2040-440: The Internet. The result was a redesign of the Internet Protocol which became eventually known as Internet Protocol Version 6 (IPv6) in 1995. IPv6 technology was in various testing stages until the mid-2000s when commercial production deployment commenced. Today, these two versions of the Internet Protocol are in simultaneous use. Among other technical changes, each version defines the format of addresses differently. Because of

2100-659: The Mobile Node. When all mobile nodes share the same IP address with the foreign agent, this is implemented by the foreign agent acting as a proxy ARP . IP address An Internet Protocol address ( IP address ) is a numerical label such as 192.0.2.1 that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface identification , and location addressing . Internet Protocol version 4 (IPv4)

2160-759: The address are the prefix, with the remaining 8 bits used for host addressing. This is equivalent to the historically used subnet mask (in this case, 255.255.255.0 ). The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA) and the five regional Internet registries (RIRs). IANA assigns blocks of IP addresses to the RIRs, which are responsible for distributing them to local Internet registries in their region such as internet service providers (ISPs) and large institutions. Some addresses are reserved for private networks and are not globally unique. Within

2220-401: The class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes ( B and C ). The following table gives an overview of this now-obsolete system. Classful network design served its purpose in the startup stage of

2280-509: The client, in which case the real originating IP address is masked from the server receiving a request. A common practice is to have a NAT mask many devices in a private network. Only the public interface(s) of the NAT needs to have an Internet-routable address. The NAT device maps different IP addresses on the private network to different TCP or UDP port numbers on the public network. In residential networks, NAT functions are usually implemented in

2340-555: The communicating node. This is needed in networks whose gateway routers check that the source IP address of the mobile host belongs to their subnet or discard the packet otherwise. In Mobile IPv6 (MIPv6), "reverse tunneling" is the default behaviour, with RO being an optional behaviour. Enhancements to the Mobile IP technique, such as Mobile IPv6 and Hierarchical Mobile IPv6 (HMIPv6) defined in RFC 5380, are being developed to improve mobile communications in certain circumstances by making

2400-505: The default configuration parameters of some network software and hardware components (e.g. netmask), and in the technical jargon used in network administrators' discussions. Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be globally unique. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved. Computers not connected to

2460-452: The devices involved in the conflict is the default gateway access beyond the LAN for all devices on the LAN, all devices may be impaired. IP addresses are classified into several classes of operational characteristics: unicast, multicast, anycast and broadcast addressing. The most common concept of an IP address is in unicast addressing, available in both IPv4 and IPv6. It normally refers to

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2520-502: The existing networks already designated by a network number. In 1981, the addressing specification was revised with the introduction of classful network architecture. Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes ( A , B , and C ) were defined for universal unicast addressing. Depending on

2580-544: The foreseeable future. The intent of the new design was not to provide just a sufficient quantity of addresses, but also redesign routing in the Internet by allowing more efficient aggregation of subnetwork routing prefixes. This resulted in slower growth of routing tables in routers. The smallest possible individual allocation is a subnet for 2 hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization ratios will be small on any IPv6 network segment. The new design also provides

2640-452: The global Internet. In a home situation, a public IP address is the IP address assigned to the home's network by the ISP . In this case, it is also locally visible by logging into the router configuration. Most public IP addresses change, and relatively often. Any type of IP address that changes is called a dynamic IP address. In home networks, the ISP usually assigns a dynamic IP. If an ISP gave

2700-469: The historical prevalence of IPv4, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of version 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5. Other versions v1 to v9 were defined, but only v4 and v6 ever gained widespread use. v1 and v2 were names for TCP protocols in 1974 and 1977, as there

2760-424: The location of the host in the network, and thus, the capability of establishing a path to that host. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there." The header of each IP packet contains the IP address of the sending host and that of the destination host. Two versions of the Internet Protocol are in common use on

2820-401: The mid-2000s, both IPv4 and IPv6 are still used side-by-side as of 2024. IPv4 addresses are usually displayed in a human-readable notation, but systems may use them in various different computer number formats . CIDR notation can also be used to designate how much of the address should be treated as a routing prefix. For example, 192.0.2.1 / 24 indicates that 24 significant bits of

2880-411: The multicast group address and the intermediary routers take care of making copies and sending them to all interested receivers (those that have joined the corresponding multicast group). Like broadcast and multicast, anycast is a one-to-many routing topology. However, the data stream is not transmitted to all receivers, just the one which the router decides is closest in the network. Anycast addressing

2940-509: The network and subnet. An IPv4 address has a size of 32 bits, which limits the address space to 4 294 967 296 (2 ) addresses. Of this number, some addresses are reserved for special purposes such as private networks (≈18 million addresses) and multicast addressing (≈270 million addresses). IPv4 addresses are usually represented in dot-decimal notation , consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 192.0.2.1 . Each part represents

3000-440: The network associated with the home agent, normal IP routing mechanisms forward these packets to the home agent. Instead of forwarding these packets to a destination that is physically in the same network as the home agent, the home agent redirects these packets towards the remote address through an IP tunnel by encapsulating the datagram with a new IP header using the care of address of the mobile node. When acting as transmitter,

3060-593: The opportunity to separate the addressing infrastructure of a network segment, i.e. the local administration of the segment's available space, from the addressing prefix used to route traffic to and from external networks. IPv6 has facilities that automatically change the routing prefix of entire networks, should the global connectivity or the routing policy change, without requiring internal redesign or manual renumbering. The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With

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3120-460: The outgoing information is transported to the home agent (which is in the home network) by means of an IP tunnel . From the Home Network, the packets of the Mobile Node can be sent using its original Home Address, without any routing problem. The Correspondent Node will send its information again to the Home Network. Thus, it has to be sent on through the tunnel to the foreign agent and then to

3180-446: The poorly defined addressing policy created ambiguities for routing. This address type was abandoned and must not be used in new systems. Addresses starting with fe80:: , called link-local addresses , are assigned to interfaces for communication on the attached link. The addresses are automatically generated by the operating system for each network interface. This provides instant and automatic communication between all IPv6 hosts on

3240-715: The processes more secure and more efficient. Fast Handovers for Mobile IPv6 is described in IETF RFC 5568. Researchers create support for mobile networking without requiring any pre-deployed infrastructure as it currently is required by MIP. One such example is Interactive Protocol for Mobile Networking (IPMN) which promises supporting mobility on a regular IP network just from the network edges by intelligent signalling between IP at end-points and application layer module with improved quality of service. Researchers are also working to create support for mobile networking between entire subnets with support from Mobile IPv6. One such example

3300-409: The reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of 192.168.0.0 through 192.168.0.255 ( 192.168.0.0 / 24 ). In IPv6, the address size was increased from 32 bits in IPv4 to 128 bits, thus providing up to 2 (approximately 3.403 × 10 ) addresses. This is deemed sufficient for

3360-405: The same IP address to a host, based on its MAC address , each time it joins the network. A network administrator may configure DHCP by allocating specific IP addresses based on MAC address. DHCP is not the only technology used to assign IP addresses dynamically. Bootstrap Protocol is a similar protocol and predecessor to DHCP. Dialup and some broadband networks use dynamic address features of

3420-457: The source or destination of packets traversing the Internet. When the link-local IPv4 address block was reserved, no standards existed for mechanisms of address autoconfiguration. Filling the void, Microsoft developed a protocol called Automatic Private IP Addressing (APIPA), whose first public implementation appeared in Windows 98 . APIPA has been deployed on millions of machines and became

3480-420: The specially defined all-nodes multicast address. A multicast address is associated with a group of interested receivers. In IPv4, addresses 224.0.0.0 through 239.255.255.255 (the former Class D addresses) are designated as multicast addresses. IPv6 uses the address block with the prefix ff00:: / 8 for multicast. In either case, the sender sends a single datagram from its unicast address to

3540-436: Was no separate IP specification at the time. v3 was defined in 1978, and v3.1 is the first version where TCP is separated from IP. v6 is a synthesis of several suggested versions, v6 Simple Internet Protocol , v7 TP/IX: The Next Internet , v8 PIP — The P Internet Protocol , and v9 TUBA — Tcp & Udp with Big Addresses . IP networks may be divided into subnetworks in both IPv4 and IPv6 . For this purpose, an IP address

3600-423: Was the first standalone specification for the IP address, and has been in use since 1983. IPv4 addresses are defined as a 32-bit number, which became too small to provide enough addresses as the internet grew, leading to IPv4 address exhaustion over the 2010s. Its designated successor, IPv6 , uses 128 bits for the IP address, giving it a larger address space . Although IPv6 deployment has been ongoing since

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