Wide Area Network

A wide area network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries [1]). This is in contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively.

WAN design options
WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet. WANs are often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. Leased lines can be very expensive. Instead of using leased lines, WANs can also be built using less costly circuit switching or packet switching methods. Network protocols including TCP/IP deliver transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relay are often used by service providers to deliver the links that are used in WANs. X.25 was an important early WAN protocol, and is often considered to be the "grandfather" of Frame Relay as many of the underlying protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.

Academic research into wide area networks can be broken down into three areas: Mathematical models, network emulation and network simulation.

Performance improvements are sometimes delivered via WAFS or WAN optimization.

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Dynamic Host Configuration Protocol

The Dynamic Host Configuration Protocol (DHCP) is a computer networking protocol used by hosts (DHCP clients) to retrieve IP address assignments and other configuration information.

DHCP uses a client-server architecture. The client sends a broadcast request for configuration information. The DHCP server receives the request and responds with configuration information from its configuration database.

In the absence of DHCP, all hosts on a network must be manually configured individually - a time-consuming and often error-prone undertaking.

Dynamic Host Configuration Protocol automates network-parameter assignment to network devices from one or more fault-tolerant DHCP servers. Even in small networks, DHCP is useful because it can make it easy to add new machines to the network.

When a DHCP-configured client (a computer or any other network-aware device) connects to a network, the DHCP client sends a broadcast query requesting necessary information from a DHCP server. The DHCP server manages a pool of IP addresses and information about client configuration parameters such as default gateway, domain name, the DNS servers, other servers such as time servers, and so forth. On receiving a valid request, the server assigns the computer an IP address, a lease (length of time the allocation is valid), and other IP configuration parameters, such as the subnet mask and the default gateway. The query is typically initiated immediately after booting, and must complete before the client can initiate IP-based communication with other hosts.

Depending on implementation, the DHCP server may have three methods of allocating IP-addresses:

dynamic allocation: A network administrator assigns a range of IP addresses to DHCP, and each client computer on the LAN has its IP software configured to request an IP address from the DHCP server during network initialization. The request-and-grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim (and then reallocate) IP addresses that are not renewed (dynamic re-use of IP addresses).
automatic allocation: The DHCP server permanently assigns a free IP address to a requesting client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.
static allocation: The DHCP server allocates an IP address based on a table with MAC address/IP address pairs, which are manually filled in (perhaps by a network administrator). Only requesting clients with a MAC address listed in this table will be allocated an IP address. This feature (which is not supported by all devices) is variously called Static DHCP Assignment (by DD-WRT), fixed-address (by the dhcpd documentation), DHCP reservation or Static DHCP (by Cisco/Linksys), and IP reservation or MAC/IP binding (by various other router manufacturers).

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IPv6

Internet Protocol version 6 (IPv6) is the next-generation Internet Protocol version designated as the successor to IPv4, the first implementation used in the Internet that is still in dominant use currently[update]. It is an Internet Layer protocol for packet-switched internetworks. The main driving force for the redesign of Internet Protocol is the foreseeable IPv4 address exhaustion. IPv6 was defined in December 1998 by the Internet Engineering Task Force (IETF) with the publication of an Internet standard specification, RFC 2460.

IPv6 has a vastly larger address space than IPv4. This results from the use of a 128-bit address, whereas IPv4 uses only 32 bits. The new address space thus supports 2128 (about 3.4×1038) addresses. This expansion provides flexibility in allocating addresses and routing traffic and eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.

IPv6 also implements new features that simplify aspects of address assignment (stateless address autoconfiguration) and network renumbering (prefix and router announcements) when changing Internet connectivity providers. The IPv6 subnet size has been standardized by fixing the size of the host identifier portion of an address to 64 bits to facilitate an automatic mechanism for forming the host identifier from Link Layer media addressing information (MAC address).

Network security is integrated into the design of the IPv6 architecture. Internet Protocol Security (IPsec) was originally developed for IPv6, but found widespread optional deployment first in IPv4 (into which it was back-engineered). The IPv6 specifications mandate IPsec implementation as a fundamental interoperability requirement.

In December 2008, despite marking its 10th anniversary as a Standards Track protocol, IPv6 was only in its infancy in terms of general worldwide deployment. A 2008 study[1] by Google Inc. indicated that penetration was still less than one percent of Internet-enabled hosts in any country. IPv6 has been implemented on all major operating systems in use in commercial, business, and home consumer environments.[2]

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Intrusion detection system

An IDS is a device (or application) that monitors network and/or system activities for malicious activities or policy violations and produces reports to a Management Station. Intrusion detection is the process of monitoring the events occurring in a computer system or network and analyzing them for signs of possible incidents, which are violations or imminent threats of violation of computer security policies, acceptable use policies, or standard security practices.[1] Intrusion prevention is the process of performing intrusion detection and attempting to stop detected possible incidents.[1] Intrusion detection and prevention systems (IDPS) are primarily focused on identifying possible incidents, logging information about them, attempting to stop them, and reporting them to security administrators.[1] In addition, organizations use IDPSs for other purposes, such as identifying problems with security policies, documenting existing threats, and deterring individuals from violating security policies.[1] IDPSs have become a necessary addition to the security infrastructure of nearly every organization.[1]

IDPSs typically record information related to observed events, notify security administrators of important observed events, and produce reports.[1] Many IDPSs can also respond to a detected threat by attempting to prevent it from succeeding.[1] They use several response techniques, which involve the IDPS stopping the attack itself, changing the security environment (e.g., reconfiguring a firewall), or changing the attack’s content.[1]

There are two main types of IDS's: network-based and host-based IDS.

In a network-based intrusion-detection system (NIDS), the sensors are located at choke points in the network to be monitored, often in the demilitarized zone (DMZ) or at network borders. The sensor captures all network traffic and analyzes the content of individual packets for malicious traffic.

In a host-based system, the sensor usually consists of a software agent, which monitors all activity of the host on which it is installed, including file system, logs and the kernel. Some application-based IDS are also part of this category.

Network intrusion detection system (NIDS)
It is an independent platform that identifies intrusions by examining network traffic and monitors multiple hosts. Network Intrusion Detection Systems gain access to network traffic by connecting to a hub, network switch configured for port mirroring, or network tap. An example of a NIDS is Snort.
Host-based intrusion detection system (HIDS)
It consists of an agent on a host that identifies intrusions by analyzing system calls, application logs, file-system modifications (binaries, password files, capability/acl databases) and other host activities and state. An example of a HIDS is OSSEC.

Intrusion detection systems can also be system-specific using custom tools and honeypots.

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Telecommunications service provider (TSP)

A telecommunications service provider or TSP is a type of communications service provider that has traditionally provided telephone and similar services. This category includes ILECs, CLECs, and mobile wireless communication companies.

While some people use the terms "telecom service provider" and "communications service provider" interchangeably, the term TSP generally excludes Internet service providers (ISPs), cable companies, satellite TV, and managed service providers.

TSPs provide access to telephone and related communications services. In the past, most TSPs were government owned and operated in most countries, due to the nature of capital expenditure involved in it. But today there are many private players in most regions of the world, and even most of the government owned companies have been privatized.

The deregulation or privatization of telecom service providers first happened in the United States with the break up of the Bell System.

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TFTP Server

Trivial File Transfer Protocol (TFTP) is a file transfer protocol, with the functionality of a very basic form of File Transfer Protocol (FTP); it was first defined in 1980.[1]

Due to its simple design, TFTP could be implemented using a very small amount of memory. It was therefore useful for booting computers such as routers which did not have any data storage devices. It is still used to transfer small amounts of data between hosts on a network, such as IP phone firmware or operating system images when a remote X Window System terminal or any other thin client boots from a network host or server. The initial stages of some network based installation systems (such as Solaris Jumpstart, Red Hat Kickstart, Symantec Ghost and Windows NT's Remote Installation Services) use TFTP to load a basic kernel that performs the actual installation.

Trivial File Transfer Protocol (TFTP) is a simple protocol to transfer files. It has been implemented on top of the User Datagram Protocol (UDP) using port number 69. TFTP is designed to be small and easy to implement, therefore, lacks most of the features of a regular FTP. TFTP only reads and writes files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication.

In TFTP, any transfer begins with a request to read or write a file, which also serves to request a connection. If the server grants the request, the connection is opened and the file is sent in fixed length blocks of 512 bytes. Each data packet contains one block of data, and must be acknowledged by an acknowledgment packet before the next packet can be sent. A data packet of less than 512 bytes signals termination of a transfer. If a packet gets lost in the network, the intended recipient will timeout and may retransmit his last packet (which may be data or an acknowledgment), thus causing the sender of the lost packet to retransmit that lost packet. The sender has to keep just one packet on hand for retransmission, since the lock step acknowledgment guarantees that all older packets have been received. Notice that both machines involved in a transfer are considered senders and receivers. One sends data and receives acknowledgments, the other sends acknowledgments and receives data.

Three modes of transfer are currently supported by TFTP: netascii, that it is 8 bit ascii; octet (This replaces the "binary" mode of previous versions of this document.) raw 8 bit bytes; mail, netascii characters sent to a user rather than a file. Additional modes can be defined by pairs of cooperating hosts.

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RIP

The Routing Information Protocol (RIP) is a dynamic routing protocol used in local and wide area networks. As such it is classified as an interior gateway protocol (IGP). It uses the distance-vector routing algorithm. It was first defined in RFC 1058 (1988). The protocol has since been extended several times, resulting in RIP Version 2 (RFC 2453). Both versions are still in use today, however, they are considered to have been made technically obsolete by more advanced techniques such as Open Shortest Path First (OSPF) and the OSI protocol IS-IS. RIP has also been adapted for use in IPv6 networks, a standard known as RIPng (RIP next generation), published in RFC 2080 (1997).

The routing algorithm used in RIP, the Bellman-Ford algorithm, was first deployed in a computer network in 1967, as the initial routing algorithm of the ARPANET.

The earliest version of the specific protocol that became RIP was the Gateway Information Protocol, part of the PARC Universal Packet internetworking protocol suite, developed at Xerox Parc. A later version, named the Routing Information Protocol, was part of Xerox Network Systems.

A version of RIP which supported the Internet Protocol (IP) was later included in the Berkeley Software Distribution (BSD) of the Unix operating system. It was known as the routed daemon. Various other vendors would create their own implementations of the routing protocol. Eventually, RFC 1058 unified the various implementations under a single standard.

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