let's learn english about network together~!

DreamCat

These term all copy from the www.speedguide.net .

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Term: Description LAN:? A local area network (LAN) is a group of computers and other network devices that share a common communications line within a small geographic area (for example, within an office building). A LAN may serve as few as two or three, or as many as thousands of users.

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Term :  Description Router: Router is the central switching device in a packet-switched network that directs and controls (routes) the flow of data.A traditional router routes packets within a single address realm, while a NAT router directs datagrams between different address realms. A NAT router sits on the border between two adress realms and performs such "transparent routing" by modifying addresses in IP headers, so that when packets enter another address realm they can be valid and routed properly.Routers are differentiated from data communications switches by the ability to perform higher-level functions necessary to the interconnection of different networks.

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Term ：Description gateway： A system (hardware-software combination) that links otherwise incompatible networks to communicate with one another.The term often refers to the server computer that links a LAN to the Internet.

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Term： Description DNS：DNS (Domain Name System) is a protocol used to translate Internet domain and host names (such as www.speedguide.net) to IP addresses. DNS implements a distributed database to store name and address information for all public hosts on the Net, assuming IP addresses are statically assigned

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Term ：Description DHCP ：DHCP (Dynamic Host Configuration Protocol) is a protocol for automatic assignment of IP addresses in an organization's network.Using the Internet Protocol, each device that can connect to the Internet needs a unique IP address assigned to it. The DHCP server assigns a dynamic IP address to each client, using the concept of a "lease" (amount of time) that the IP will be valid for a particular network node. Assigning short lease times to clients allows for a dynamic network with more nodes than available IP addresses.With DHCP there is no need to statically assign IPs to each node locally, and there is no need to reconfigure clients if they are moved to a different place in the network. The only disadvantage of using DHCP is the fact clients have no permanent IP addresses; when the DHCP lease expires IPs can be reassigned to a different client.

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Term ：Description broadband ：broadband is a term that is being used interchangeably with high-speed. More specifically, it desctibes a wideband high-speed data transmission that employs only one wire, which is able to carry multiple channels at once (as opposed to narrowband, or baseband which transmits one channel at a time).Various definitions of broadband assign a different minimum data rate to the term, however it is generally agreed that DSL and Cable are broadband services in the downstream direction.

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Term： Description WAN ：WAN (Wide Area Network) is a telecommunications network that covers a large area, such as a state or country, spanning multiple LANs. The term often suggests the inclusion of public (shared user) networks.

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Term ：Description IP Address： IP Address (Internet Protocol Address) is used to identify a computer to a network. It is, in essence your address on the Internet. Each packet of data on the Internet contains the source and destination IP address, so information can be routed accordingly. Note: Some IP addresses are internal to your local network, and not routable to the Internet. The following 3 blocks of the IP address space have been reserved by the Internet Assigned Numbers Authority (IANA) for private Intranets: 10.0.0.0 - 10.255.255.255 (10/8 prefix)172.16.0.0 - 172.31.255.255 (172.16/12 prefix)192.168.0.0 - 192.168.255.255 (192.168/16 prefix) If your PC is assigned an IP address in one of the above ranges, it is most probably behind a firewall, running NAT or SOCKS. In this case, the IP packets sent to the Internet are addressed from the firewall, and not from your PC.

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Term :   Description packet : packet (a.k.a. datagram, transmission unit) is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. Any information transmitted over the Internet is divided by the TCP (Transmission Control Protocol) layer into "chunks" or packets of an efficient size for routing

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proxy : A proxy server is an intermediate gateway that sits between a client PC and the Internet and provices forwarding/caching service, as well as security, logging and administrative control.A caching web proxy server saves content (such as Web pages) in its local cache the first time a request is made, and then serves the pages to other local clients from cache, without the need to forward the request to the Internet. Pages are only requested from the Internet if they are not found in cache. The proxy server forwards requests acting as a client, with its own IP address, and then in turn serves the pages to local clients.Caching proxy servers offer transparent service to clients, they can save bandwidth and improve performance, however they can also cause slowdowns when congested, as well as some problems delivering dynamic and secure content

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NAT： NAT (Network Address Translation) is an IETF standard that enables LANs to use one set of private IP addresses for internal traffic an another set of IPs for external traffic. Typically, a NAT device makes all IP address translations where the LAN meets the WAN.NAT permits a large number of LAN users to share one external IP address, and adds some network security, since private IP address ranges are not routable outside the LAN.The following 3 blocks of the IP address space have been reserved by the Internet Assigned Numbers Authority (IANA) for private Intranets:10.0.0.0 - 10.255.255.255 (class A, 10/8 prefix)172.16.0.0 - 172.31.255.255 (class B range, 172.16/12 prefix)192.168.0.0 - 192.168.255.255 (class C range, 192.168/16 prefix)Resources: NAT-RFC1631, Private IPs - RFC1918

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MTU MTU (Maximum Transmission Unit) is the greatest amount of data that can be transferred in one physical frame on the network. If a packet that has a smaller MTU than the packet's frame length is sent, fragmentation will occur. For TCP (Transmission Control Protocol) MTU can range from 68 to 1500 bytes. Larger MTUs provide for lower overhead (fewer headers).

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broadband broadband is a term that is being used interchangeably with high-speed. More specifically, it desctibes a wideband high-speed data transmission that employs only one wire, which is able to carry multiple channels at once (as opposed to narrowband, or baseband which transmits one channel at a time).Various definitions of broadband assign a different minimum data rate to the term, however it is generally agreed that DSL and Cable are broadband services in the downstream direction

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PPPoE PPPoE ( Point-to-Point Protocol over Ethernet ) is a method for building PPP sessions and encapsulating packets, as described in RFC2516. Although it is not a standard, PPPoE is already being used by a number of DSL providers. It requires either routers that have built-in PPPoE support, or PPPoE software to "dial up" and establish the session

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RWIN RWIN (TCP Receive Window) is a buffer that determines how much data the receiving computer is prepared to get at one time.A RWIN value that's too large will result in greater loss of data if a packet is lost or damaged. A too small RWIN will be very slow, as each packet will have to be acknowledged before the next packet is sent.RWIN is one of the most important parameters in tweaking any TCP/IP connection