94-695: Internet2 is a not-for-profit United States computer networking consortium led by members from the research and education communities, industry, and government. The Internet2 consortium administrative headquarters are located in Ann Arbor, Michigan , with offices in Washington, D.C. , and Emeryville, California . As of November 2013, Internet2 has over 500 members including 251 institutions of higher education, 9 partners and 76 members from industry, over 100 research and education networks or connector organizations, and 67 affiliate members. Internet2 operates
188-507: A link-local address , which have the prefix fe80:: / 10 . This prefix is followed by 54 bits that can be used for subnetting, although they are typically set to zeros, and a 64-bit interface identifier. The host can compute and assign the Interface identifier by itself without the presence or cooperation of an external network component like a DHCP server, in a process called link-local address autoconfiguration . The lower 64 bits of
282-513: A local area network (LAN) by sending a neighbor solicitation message asking for the link-layer address of the IP address. If any other host in the LAN is using that address, it responds. A host bringing up a new IPv6 interface first generates a unique link-local address using one of several mechanisms designed to generate a unique address. Should a non-unique address be detected, the host can try again with
376-756: A protocol stack , often constructed per the OSI model, communications functions are divided up into protocol layers, where each layer leverages the services of the layer below it until the lowest layer controls the hardware that sends information across the media. The use of protocol layering is ubiquitous across the field of computer networking. An important example of a protocol stack is HTTP (the World Wide Web protocol) running over TCP over IP (the Internet protocols) over IEEE 802.11 (the Wi-Fi protocol). This stack
470-468: A 6 bit Differentiated Services Code Point and a 2-bit Explicit Congestion Notification field. Extension headers carry options that are used for special treatment of a packet in the network, e.g., for routing, fragmentation, and for security using the IPsec framework. Without special options, a payload must be less than 64 kB . With a Jumbo Payload option (in a Hop-By-Hop Options extension header),
564-519: A Draft Standard for the IETF, which subsequently ratified it as an Internet Standard on 14 July 2017. Devices on the Internet are assigned a unique IP address for identification and location definition. With the rapid growth of the Internet after commercialization in the 1990s, it became evident that far more addresses would be needed to connect devices than the IPv4 address space had available. By 1998,
658-503: A diverse set of networking capabilities. The protocols have a flat addressing scheme. They operate mostly at layers 1 and 2 of the OSI model. For example, MAC bridging ( IEEE 802.1D ) deals with the routing of Ethernet packets using a Spanning Tree Protocol . IEEE 802.1Q describes VLANs , and IEEE 802.1X defines a port-based network access control protocol, which forms the basis for the authentication mechanisms used in VLANs (but it
752-556: A faster alternative to the Internet. Many fields have been able to use the Abilene network to foster creativity, research, and development in a way that was not previously possible. Users of poor quality libraries can now download not only text but sound recordings, animations, videos, and other resources, which would be otherwise unavailable. Another application is the robust video conferencing now available to Internet2 participants. Neurosurgeons can now video conference with other experts in
846-440: A large, congested network into an aggregation of smaller, more efficient networks. A router is an internetworking device that forwards packets between networks by processing the addressing or routing information included in the packet. The routing information is often processed in conjunction with the routing table . A router uses its routing table to determine where to forward packets and does not require broadcasting packets which
940-599: A minimum set of cryptographic algorithms . This requirement will help to make IPsec implementations more interoperable between devices from different vendors. The IPsec Authentication Header (AH) and the Encapsulating Security Payload header (ESP) are implemented as IPv6 extension headers. The packet header in IPv6 is simpler than the IPv4 header. Many rarely used fields have been moved to optional header extensions. The IPv6 packet header has simplified
1034-440: A multi-port bridge. Switches normally have numerous ports, facilitating a star topology for devices, and for cascading additional switches. Bridges and switches operate at the data link layer (layer 2) of the OSI model and bridge traffic between two or more network segments to form a single local network. Both are devices that forward frames of data between ports based on the destination MAC address in each frame. They learn
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#17327799854931128-505: A new connectivity provider with different routing prefixes is a major effort with IPv4. With IPv6, however, changing the prefix announced by a few routers can in principle renumber an entire network, since the host identifiers (the least-significant 64 bits of an address) can be independently self-configured by a host. The SLAAC address generation method is implementation-dependent. IETF recommends that addresses be deterministic but semantically opaque. Internet Protocol Security (IPsec)
1222-597: A new mechanism for mapping IP addresses to link-layer addresses (e.g. MAC addresses ), because it does not support the broadcast addressing method, on which the functionality of the Address Resolution Protocol (ARP) in IPv4 is based. IPv6 implements the Neighbor Discovery Protocol (NDP, ND) in the link layer , which relies on ICMPv6 and multicast transmission. IPv6 hosts verify the uniqueness of their IPv6 addresses in
1316-456: A newly generated address. Once a unique link-local address is established, the IPv6 host determines whether the LAN is connected on this link to any router interface that supports IPv6. It does so by sending out an ICMPv6 router solicitation message to the all-routers multicast group with its link-local address as source. If there is no answer after a predetermined number of attempts, the host concludes that no routers are connected. If it does get
1410-714: A particular privacy concern for mobile devices, such as laptops and cell phones. To address these privacy concerns, the SLAAC protocol includes what are typically called "privacy addresses" or, more correctly, "temporary addresses". Temporary addresses are random and unstable. A typical consumer device generates a new temporary address daily and will ignore traffic addressed to an old address after one week. Temporary addresses are used by default by Windows since XP SP1, macOS since (Mac OS X) 10.7, Android since 4.0, and iOS since version 4.3. Use of temporary addresses by Linux distributions varies. Renumbering an existing network for
1504-457: A repeater hub assists with collision detection and fault isolation for the network. Hubs and repeaters in LANs have been largely obsoleted by modern network switches. Network bridges and network switches are distinct from a hub in that they only forward frames to the ports involved in the communication whereas a hub forwards to all ports. Bridges only have two ports but a switch can be thought of as
1598-523: A self-generated link-local address and, when connected to a network, conflict resolution is performed and routers provide network prefixes via router advertisements. Stateless configuration of routers can be achieved with a special router renumbering protocol. When necessary, hosts may configure additional stateful addresses via Dynamic Host Configuration Protocol version 6 (DHCPv6) or static addresses manually. Like IPv4, IPv6 supports globally unique IP addresses . The design of IPv6 intended to re-emphasize
1692-418: A single failure can cause the network to fail entirely. In general, the more interconnections there are, the more robust the network is; but the more expensive it is to install. Therefore, most network diagrams are arranged by their network topology which is the map of logical interconnections of network hosts. Common topologies are: The physical layout of the nodes in a network may not necessarily reflect
1786-403: A standard voice telephone line. Modems are still commonly used for telephone lines, using a digital subscriber line technology and cable television systems using DOCSIS technology. A firewall is a network device or software for controlling network security and access rules. Firewalls are inserted in connections between secure internal networks and potentially insecure external networks such as
1880-877: A transmission medium. Power line communication uses a building's power cabling to transmit data. The following classes of wired technologies are used in computer networking. Network connections can be established wirelessly using radio or other electromagnetic means of communication. The last two cases have a large round-trip delay time , which gives slow two-way communication but does not prevent sending large amounts of information (they can have high throughput). Apart from any physical transmission media, networks are built from additional basic system building blocks, such as network interface controllers , repeaters , hubs , bridges , switches , routers , modems, and firewalls . Any particular piece of equipment will frequently contain multiple building blocks and so may perform multiple functions. A network interface controller (NIC)
1974-406: A variety of network topologies . The nodes of a computer network can include personal computers , servers , networking hardware , or other specialized or general-purpose hosts . They are identified by network addresses and may have hostnames . Hostnames serve as memorable labels for the nodes and are rarely changed after initial assignment. Network addresses serve for locating and identifying
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#17327799854932068-495: A variety of different sources, primarily to support circuit-switched digital telephony . However, due to its protocol neutrality and transport-oriented features, SONET/SDH also was the obvious choice for transporting Asynchronous Transfer Mode (ATM) frames. Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells . This differs from other protocols such as
2162-657: A virtual system of links that run on top of the Internet . Overlay networks have been used since the early days of networking, back when computers were connected via telephone lines using modems, even before data networks were developed. The most striking example of an overlay network is the Internet itself. The Internet itself was initially built as an overlay on the telephone network . Even today, each Internet node can communicate with virtually any other through an underlying mesh of sub-networks of wildly different topologies and technologies. Address resolution and routing are
2256-460: Is /22 or 1024 IPv4 addresses. A LIR may receive additional allocation when about 80% of all the address space has been utilized. RIPE NCC announced that it had fully run out of IPv4 addresses on 25 November 2019, and called for greater progress on the adoption of IPv6. On the Internet, data is transmitted in the form of network packets . IPv6 specifies a new packet format , designed to minimize packet header processing by routers. Because
2350-522: Is computer hardware that connects the computer to the network media and has the ability to process low-level network information. For example, the NIC may have a connector for plugging in a cable, or an aerial for wireless transmission and reception, and the associated circuitry. In Ethernet networks, each NIC has a unique Media Access Control (MAC) address —usually stored in the controller's permanent memory. To avoid address conflicts between network devices,
2444-426: Is 1280 octets . Unlike mobile IPv4, mobile IPv6 avoids triangular routing and is therefore as efficient as native IPv6. IPv6 routers may also allow entire subnets to move to a new router connection point without renumbering. The IPv6 packet header has a minimum size of 40 octets (320 bits). Options are implemented as extensions. This provides the opportunity to extend the protocol in the future without affecting
2538-422: Is a virtual network that is built on top of another network. Nodes in the overlay network are connected by virtual or logical links. Each link corresponds to a path, perhaps through many physical links, in the underlying network. The topology of the overlay network may (and often does) differ from that of the underlying one. For example, many peer-to-peer networks are overlay networks. They are organized as nodes of
2632-566: Is also found in WLANs ) – it is what the home user sees when the user has to enter a "wireless access key". Ethernet is a family of technologies used in wired LANs. It is described by a set of standards together called IEEE 802.3 published by the Institute of Electrical and Electronics Engineers. Wireless LAN based on the IEEE 802.11 standards, also widely known as WLAN or WiFi, is probably
2726-478: Is an electronic device that receives a network signal , cleans it of unnecessary noise and regenerates it. The signal is retransmitted at a higher power level, or to the other side of obstruction so that the signal can cover longer distances without degradation. In most twisted-pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. With fiber optics, repeaters can be tens or even hundreds of kilometers apart. Repeaters work on
2820-570: Is defined as 0000:0000:0000:0000:0000:0000:0000:0001 and is abbreviated to ::1 by using both rules. As an IPv6 address may have more than one representation, the IETF has issued a proposed standard for representing them in text . Because IPv6 addresses contain colons, and URLs use colons to separate the host from the port number, an IPv6 address used as the host-part of a URL should be enclosed in square brackets, e.g. http://[2001:db8:4006:812::200e] or http://[2001:db8:4006:812::200e]:8080/path/page.html. All interfaces of IPv6 hosts require
2914-522: Is indicated by the Jumbo Payload Option extension header. An IPv6 packet has two parts: a header and payload . The header consists of a fixed portion with minimal functionality required for all packets and may be followed by optional extensions to implement special features. The fixed header occupies the first 40 octets (320 bits) of the IPv6 packet. It contains the source and destination addresses, traffic class, hop count, and
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3008-412: Is inefficient for very big networks. Modems (modulator-demodulator) are used to connect network nodes via wire not originally designed for digital network traffic, or for wireless. To do this one or more carrier signals are modulated by the digital signal to produce an analog signal that can be tailored to give the required properties for transmission. Early modems modulated audio signals sent over
3102-485: Is its larger address space. The size of an IPv6 address is 128 bits, compared to 32 bits in IPv4. The address space therefore has 2 =340,282,366,920,938,463,463,374,607,431,768,211,456 addresses (340 undecillion , approximately 3.4 × 10 ). Some blocks of this space and some specific addresses are reserved for special uses . While this address space is very large, it was not the intent of the designers of IPv6 to assure geographical saturation with usable addresses. Rather,
3196-404: Is not sending packets, the link can be filled with packets from other users, and so the cost can be shared, with relatively little interference, provided the link is not overused. Often the route a packet needs to take through a network is not immediately available. In that case, the packet is queued and waits until a link is free. The physical link technologies of packet networks typically limit
3290-445: Is possible to embed the unicast address prefix into the IPv6 multicast address format, while still providing a 32-bit block, the least significant bits of the address, or approximately 4.2 billion multicast group identifiers. Thus each user of an IPv6 subnet automatically has available a set of globally routable source-specific multicast groups for multicast applications. IPv6 hosts configure themselves automatically. Every interface has
3384-568: Is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet . IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion , and was intended to replace IPv4 . In December 1998, IPv6 became
3478-533: Is the process of selecting network paths to carry network traffic. Routing is performed for many kinds of networks, including circuit switching networks and packet switched networks. IPv6 Early research and development: Merging the networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: Internet Protocol version 6 ( IPv6 )
3572-459: Is used between the wireless router and the home user's personal computer when the user is surfing the web. There are many communication protocols, a few of which are described below. The Internet protocol suite , also called TCP/IP, is the foundation of all modern networking. It offers connection-less and connection-oriented services over an inherently unreliable network traversed by datagram transmission using Internet protocol (IP). At its core,
3666-455: Is written as four hexadecimal digits (sometimes called hextets or more formally hexadectets and informally a quibble or quad-nibble ) and the groups are separated by colons (:). An example of this representation is 2001:0db8:0000:0000:0000:ff00:0042:8329 . For convenience and clarity, the representation of an IPv6 address may be shortened with the following rules: An example of application of these rules: The loopback address
3760-462: The Institute of Electrical and Electronics Engineers (IEEE) maintains and administers MAC address uniqueness. The size of an Ethernet MAC address is six octets . The three most significant octets are reserved to identify NIC manufacturers. These manufacturers, using only their assigned prefixes, uniquely assign the three least-significant octets of every Ethernet interface they produce. A repeater
3854-597: The Réseaux IP Européens Network Coordination Centre (RIPE NCC), Latin America and Caribbean Network Information Centre (LACNIC), and American Registry for Internet Numbers (ARIN) have reached this stage. This leaves African Network Information Center (AFRINIC) as the sole regional internet registry that is still using the normal protocol for distributing IPv4 addresses. As of November 2018, AFRINIC's minimum allocation
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3948-477: The World Wide Web , digital video and audio , shared use of application and storage servers , printers and fax machines , and use of email and instant messaging applications. Computer networking may be considered a branch of computer science , computer engineering , and telecommunications , since it relies on the theoretical and practical application of the related disciplines. Computer networking
4042-466: The transport layer . Thus, while IPv4 allowed UDP datagram headers to have no checksum (indicated by 0 in the header field), IPv6 requires a checksum in UDP headers. IPv6 routers do not perform IP fragmentation . IPv6 hosts are required to do one of the following: perform Path MTU Discovery , perform end-to-end fragmentation, or send packets no larger than the default maximum transmission unit (MTU), which
4136-410: The IETF had formalized the successor protocol. IPv6 uses 128- bit addresses, theoretically allowing 2 , or approximately 3.4 × 10 total addresses. The actual number is slightly smaller, as multiple ranges are reserved for special usage or completely excluded from general use. The two protocols are not designed to be interoperable , and thus direct communication between them is impossible, complicating
4230-568: The IPv6 header furthers the end-to-end principle of Internet design, which envisioned that most processing in the network occurs in the leaf nodes. Integrity protection for the data that is encapsulated in the IPv6 packet is assumed to be assured by both the link layer or error detection in higher-layer protocols, namely the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) on
4324-440: The Internet protocol suite or Ethernet that use variable-sized packets or frames . ATM has similarities with both circuit and packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before
4418-574: The Internet. Firewalls are typically configured to reject access requests from unrecognized sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in cyber attacks . A communication protocol is a set of rules for exchanging information over a network. Communication protocols have various characteristics. They may be connection-oriented or connectionless , they may use circuit mode or packet switching, and they may use hierarchical addressing or flat addressing. In
4512-910: The Internet2 Network, an Internet Protocol network using optical fiber that delivers network services for research and education, and provides a secure network testing and research environment. In late 2007, Internet2 began operating its newest dynamic circuit network , the Internet2 DCN, an advanced technology that allows user-based allocation of data circuits over the fiber-optic network. The Internet2 Network, through its regional network and connector members, connects over 60,000 U.S. educational, research, government and "community anchor" institutions, from primary and secondary schools to community colleges and universities, public libraries and museums to health care organizations. The Internet2 community develops and deploys network technologies for
4606-480: The Internet2 Network. In 2010, Internet2 received a $ 62.5 million American Recovery and Reinvestment Act grant, which allowed Internet2 to put in place a long term IRU for fiber and upgrade the network with its own DWDM optical network system. Ciena later announced that this was the first 100G nationwide optical network. The upgrade to the new optical system was completed in December 2012. Internet2 provides
4700-481: The U.S. research and education community with a network that satisfies their bandwidth-intensive requirements. The network itself is a dynamic, robust and cost-effective hybrid optical and packet network. It furnishes a 100 Gbit/s network backbone to more than 210 U.S. educational institutions, 70 corporations and 45 non-profit and government agencies. The objectives of the Internet2 consortium are: The uses of
4794-627: The actual data exchange begins. ATM still plays a role in the last mile , which is the connection between an Internet service provider and the home user. There are a number of different digital cellular standards, including: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), cdmaOne , CDMA2000 , Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS-136/TDMA), and Integrated Digital Enhanced Network (iDEN). Routing
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#17327799854934888-468: The association of physical ports to MAC addresses by examining the source addresses of received frames and only forward the frame when necessary. If an unknown destination MAC is targeted, the device broadcasts the request to all ports except the source, and discovers the location from the reply. Bridges and switches divide the network's collision domain but maintain a single broadcast domain. Network segmentation through bridging and switching helps break down
4982-562: The award are announced each year at the Spring member meeting: 2006, 2007, 2008. Computer network A computer network is a set of computers sharing resources located on or provided by network nodes . Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical , and wireless radio-frequency methods that may be arranged in
5076-461: The core packet structure. However, RFC 7872 notes that some network operators drop IPv6 packets with extension headers when they traverse transit autonomous systems . IPv4 limits packets to 65,535 (2 −1) octets of payload. An IPv6 node can optionally handle packets over this limit, referred to as jumbograms , which can be as large as 4,294,967,295 (2 −1) octets. The use of jumbograms may improve performance over high- MTU links. The use of jumbograms
5170-558: The creation of the very-high-performance Backbone Network Service, or vBNS , developed in 1995 by the National Science Foundation (NSF) and MCI for supercomputers at educational institutions. After the expiration of the NSF agreement, vBNS largely transitioned to providing service to the government. As a result, the research and education community founded Internet2 to serve its networking needs. The Internet2 Project
5264-543: The delivery of services. Device mobility, security, and configuration aspects have been considered in the design of the protocol. IPv6 addresses are represented as eight groups of four hexadecimal digits each, separated by colons. The full representation may be shortened; for example, 2001:0db8:0000:0000:0000:8a2e:0370:7334 becomes 2001:db8::8a2e:370:7334 . IPv6 is an Internet Layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks, closely adhering to
5358-418: The deployment of inter-domain solutions. In IPv4 it is very difficult for an organization to get even one globally routable multicast group assignment, and the implementation of inter-domain solutions is arcane. Unicast address assignments by a local Internet registry for IPv6 have at least a 64-bit routing prefix, yielding the smallest subnet size available in IPv6 (also 64 bits). With such an assignment it
5452-444: The design principles developed in the previous version of the protocol, Internet Protocol Version 4 (IPv4). In addition to offering more addresses, IPv6 also implements features not present in IPv4. It simplifies aspects of address configuration, network renumbering, and router announcements when changing network connectivity providers. It simplifies packet processing in routers by placing the responsibility for packet fragmentation in
5546-562: The early 1990s, even after the redesign of the addressing system using a classless network model, it became clear that this would not suffice to prevent IPv4 address exhaustion , and that further changes to the Internet infrastructure were needed. The last unassigned top-level address blocks of 16 million IPv4 addresses were allocated in February 2011 by the Internet Assigned Numbers Authority (IANA) to
5640-446: The end points. The IPv6 subnet size is standardized by fixing the size of the host identifier portion of an address to 64 bits. The addressing architecture of IPv6 is defined in RFC 4291 and allows three different types of transmission: unicast , anycast and multicast . Internet Protocol Version 4 (IPv4) was the first publicly used version of the Internet Protocol . IPv4
5734-401: The end-to-end principle of network design that was originally conceived during the establishment of the early Internet by rendering network address translation obsolete. Therefore, every device on the network is globally addressable directly from any other device. A stable, unique, globally addressable IP address would facilitate tracking a device across networks. Therefore, such addresses are
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#17327799854935828-419: The field during an operation in a high resolution format with no apparent time lag. The Internet2 Driving Exemplary Applications (IDEA) award (not to be confused with IDEA awards ) was first announced by Internet2 in 2006 as a way of recognizing those who create and use advanced network applications at their best. The judging is conducted by many universities and based upon the following criteria: Winners of
5922-547: The five regional Internet registries (RIRs). However, each RIR still has available address pools and is expected to continue with standard address allocation policies until one /8 Classless Inter-Domain Routing (CIDR) block remains. After that, only blocks of 1,024 addresses (/22) will be provided from the RIRs to a local Internet registry (LIR). As of September 2015, all of Asia-Pacific Network Information Centre (APNIC),
6016-451: The future of the Internet. These technologies include large-scale network performance measurement and management tools, secure identity and access management tools and capabilities such as scheduling high-bandwidth, high-performance circuits. Internet2 members serve on several advisory councils, collaborate in a variety of working groups and special interest groups, gather at spring and fall member meetings, and are encouraged to participate in
6110-484: The headers of IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable. However, most transport and application-layer protocols need little or no change to operate over IPv6; exceptions are application protocols that embed Internet-layer addresses, such as File Transfer Protocol (FTP) and Network Time Protocol (NTP), where the new address format may cause conflicts with existing protocol syntax. The main advantage of IPv6 over IPv4
6204-413: The large subnet space and hierarchical route aggregation. Multicasting , the transmission of a packet to multiple destinations in a single send operation, is part of the base specification in IPv6. In IPv4 this is an optional (although commonly implemented) feature. IPv6 multicast addressing has features and protocols in common with IPv4 multicast, but also provides changes and improvements by eliminating
6298-499: The link-local address (the suffix) were originally derived from the MAC address of the underlying network interface card. As this method of assigning addresses would cause undesirable address changes when faulty network cards were replaced, and as it also suffered from a number of security and privacy issues, RFC 8064 has replaced the original MAC-based method with the hash-based method specified in RFC 7217 . IPv6 uses
6392-668: The literature as the physical medium ) used to link devices to form a computer network include electrical cable , optical fiber , and free space. In the OSI model , the software to handle the media is defined at layers 1 and 2 — the physical layer and the data link layer. A widely adopted family that uses copper and fiber media in local area network (LAN) technology are collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet are defined by IEEE 802.3 . Wireless LAN standards use radio waves , others use infrared signals as
6486-525: The longer addresses simplify allocation of addresses, enable efficient route aggregation , and allow implementation of special addressing features. In IPv4, complex Classless Inter-Domain Routing (CIDR) methods were developed to make the best use of the small address space. The standard size of a subnet in IPv6 is 2 addresses, about four billion times the size of the entire IPv4 address space. Thus, actual address space utilization will be small in IPv6, but network management and routing efficiency are improved by
6580-665: The means that allow mapping of a fully connected IP overlay network to its underlying network. Another example of an overlay network is a distributed hash table , which maps keys to nodes in the network. In this case, the underlying network is an IP network, and the overlay network is a table (actually a map ) indexed by keys. Overlay networks have also been proposed as a way to improve Internet routing, such as through quality of service guarantees achieve higher-quality streaming media . Previous proposals such as IntServ , DiffServ , and IP multicast have not seen wide acceptance largely because they require modification of all routers in
6674-415: The most well-known member of the IEEE 802 protocol family for home users today. IEEE 802.11 shares many properties with wired Ethernet. Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers. They were originally designed to transport circuit mode communications from
6768-450: The move to IPv6. However, several transition mechanisms have been devised to rectify this. IPv6 provides other technical benefits in addition to a larger addressing space. In particular, it permits hierarchical address allocation methods that facilitate route aggregation across the Internet, and thus limit the expansion of routing tables . The use of multicast addressing is expanded and simplified, and provides additional optimization for
6862-578: The need for certain protocols. IPv6 does not implement traditional IP broadcast , i.e. the transmission of a packet to all hosts on the attached link using a special broadcast address , and therefore does not define broadcast addresses. In IPv6, the same result is achieved by sending a packet to the link-local all nodes multicast group at address ff02::1, which is analogous to IPv4 multicasting to address 224.0.0.1. IPv6 also provides for new multicast implementations, including embedding rendezvous point addresses in an IPv6 multicast group address, which simplifies
6956-412: The network needs to deliver the user data, for example, source and destination network addresses , error detection codes, and sequencing information. Typically, control information is found in packet headers and trailers , with payload data in between. With packets, the bandwidth of the transmission medium can be better shared among users than if the network were circuit switched . When one user
7050-401: The network span from collaborative applications, distributed research experiments, grid-based data analysis to social networking. Some of these applications are in varying levels of commercialization, such as IPv6 , open-source middleware for secure network access, Layer 2 VPNs and dynamic circuit networks . These technologies and their organizational counterparts were not only created to make
7144-420: The network topology. As an example, with FDDI , the network topology is a ring, but the physical topology is often a star, because all neighboring connections can be routed via a central physical location. Physical layout is not completely irrelevant, however, as common ducting and equipment locations can represent single points of failure due to issues like fires, power failures and flooding. An overlay network
7238-729: The network. On the other hand, an overlay network can be incrementally deployed on end-hosts running the overlay protocol software, without cooperation from Internet service providers . The overlay network has no control over how packets are routed in the underlying network between two overlay nodes, but it can control, for example, the sequence of overlay nodes that a message traverses before it reaches its destination . For example, Akamai Technologies manages an overlay network that provides reliable, efficient content delivery (a kind of multicast ). Academic research includes end system multicast, resilient routing and quality of service studies, among others. The transmission media (often referred to in
7332-427: The nodes by communication protocols such as the Internet Protocol . Computer networks may be classified by many criteria, including the transmission medium used to carry signals, bandwidth , communications protocols to organize network traffic , the network size, the topology, traffic control mechanisms, and organizational intent. Computer networks support many applications and services , such as access to
7426-413: The payload must be less than 4 GB. Unlike with IPv4, routers never fragment a packet. Hosts are expected to use Path MTU Discovery to make their packets small enough to reach the destination without needing to be fragmented. See IPv6 packet fragmentation . IPv6 addresses have 128 bits. The design of the IPv6 address space implements a different design philosophy than in IPv4, in which subnetting
7520-520: The physical layer of the OSI model but still require a small amount of time to regenerate the signal. This can cause a propagation delay that affects network performance and may affect proper function. As a result, many network architectures limit the number of repeaters used in a network, e.g., the Ethernet 5-4-3 rule . An Ethernet repeater with multiple ports is known as an Ethernet hub . In addition to reconditioning and distributing network signals,
7614-532: The process of packet forwarding by routers . Although IPv6 packet headers are at least twice the size of IPv4 packet headers, processing of packets that only contain the base IPv6 header by routers may, in some cases, be more efficient, because less processing is required in routers due to the headers being aligned to match common word sizes . However, many devices implement IPv6 support in software (as opposed to hardware), thus resulting in very bad packet processing performance. Additionally, for many implementations,
7708-456: The protocol suite defines the addressing, identification, and routing specifications for Internet Protocol Version 4 (IPv4) and for IPv6 , the next generation of the protocol with a much enlarged addressing capability. The Internet protocol suite is the defining set of protocols for the Internet. IEEE 802 is a family of IEEE standards dealing with local area networks and metropolitan area networks. The complete IEEE 802 protocol suite provides
7802-409: The range 0 to 255, or 8 bits per number. Thus, IPv4 provides an addressing capability of 2 or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be a test of DARPA's networking concepts. During the first decade of operation of the Internet, it became apparent that methods had to be developed to conserve address space. In
7896-515: The sharing of files and information, giving authorized users access to data stored on other computers. Distributed computing leverages resources from multiple computers across a network to perform tasks collaboratively. Most modern computer networks use protocols based on packet-mode transmission. A network packet is a formatted unit of data carried by a packet-switched network . Packets consist of two types of data: control information and user data (payload). The control information provides data
7990-493: The size of packets to a certain maximum transmission unit (MTU). A longer message may be fragmented before it is transferred and once the packets arrive, they are reassembled to construct the original message. The physical or geographic locations of network nodes and links generally have relatively little effect on a network, but the topology of interconnections of a network can significantly affect its throughput and reliability. With many technologies, such as bus or star networks,
8084-451: The strategic planning process. As the Internet gained in public recognition and popularity, universities were among the first institutions to outgrow the Internet's bandwidth limitations because of the data transfer requirements faced by academic researchers who needed to collaborate with their colleagues. Some universities wanted to support high-performance applications like data mining, medical imaging and particle physics. This resulted in
8178-516: The type of the optional extension or payload which follows the header. This Next Header field tells the receiver how to interpret the data which follows the header. If the packet contains options, this field contains the option type of the next option. The "Next Header" field of the last option points to the upper-layer protocol that is carried in the packet's payload . The current use of the IPv6 Traffic Class field divides this between
8272-408: The use of Extension Headers causes packets to be processed by a router's CPU, leading to poor performance or even security issues. Moreover, an IPv6 header does not include a checksum. The IPv4 header checksum is calculated for the IPv4 header, and has to be recalculated by routers every time the time to live (called hop limit in the IPv6 protocol) is reduced by one. The absence of a checksum in
8366-700: Was a prime investor in the National LambdaRail (NLR) project. During 2004–2006, Internet2 and NLR held extensive discussions regarding a possible merger. Those talks paused in spring, 2006, resumed in March, 2007, but eventually ceased in the fall of 2007, due to unresolved differences. In 2006, Internet2 announced a partnership with Level 3 Communications to launch a brand new nationwide network, boosting its capacity from 10 Gbit/s to 100 Gbit/s. In October, 2007, Internet2 officially retired Abilene and now refers to its new, higher capacity network as
8460-518: Was developed as a research project by the Defense Advanced Research Projects Agency (DARPA), a United States Department of Defense agency , before becoming the foundation for the Internet and the World Wide Web . IPv4 includes an addressing system that uses numerical identifiers consisting of 32 bits. These addresses are typically displayed in dot-decimal notation as decimal values of four octets, each in
8554-462: Was influenced by a wide array of technological developments and historical milestones. Computer networks enhance how users communicate with each other by using various electronic methods like email, instant messaging, online chat, voice and video calls, and video conferencing. Networks also enable the sharing of computing resources. For example, a user can print a document on a shared printer or use shared storage devices. Additionally, networks allow for
8648-571: Was originally developed for IPv6, but found widespread deployment first in IPv4, for which it was re-engineered. IPsec was a mandatory part of all IPv6 protocol implementations, and Internet Key Exchange (IKE) was recommended, but with RFC 6434 the inclusion of IPsec in IPv6 implementations was downgraded to a recommendation because it was considered impractical to require full IPsec implementation for all types of devices that may use IPv6. However, as of RFC 4301 IPv6 protocol implementations that do implement IPsec need to implement IKEv2 and need to support
8742-433: Was originally established by 34 university researchers in 1996 under the auspices of EDUCOM (later EDUCAUSE ), and was formally organized as the not-for-profit University Corporation for Advanced Internet Development (UCAID) in 1997. It later changed its name to Internet2. Internet2 is a registered trademark. The Internet2 community, in partnership with Qwest , built the first Internet2 Network, called Abilene , in 1998 and
8836-666: Was used to improve the efficiency of utilization of the small address space. In IPv6, the address space is deemed large enough for the foreseeable future, and a local area subnet always uses 64 bits for the host portion of the address, designated as the interface identifier, while the most-significant 64 bits are used as the routing prefix. While the myth has existed regarding IPv6 subnets being impossible to scan, RFC 7707 notes that patterns resulting from some IPv6 address configuration techniques and algorithms allow address scanning in many real-world scenarios. The 128 bits of an IPv6 address are represented in 8 groups of 16 bits each. Each group
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