TTL TTL (Time To Live) is a value set in the header of outgoing IP packets. TTL determines the maximum amount of time (in seconds) an IP packet can live, or the number of routers an IP packet may pass through before being discarded (whichever is lower). QUOTE
header header refers to the first part of a data cell or packet, containing such information as source and destination addresses, and instructions on how the telecommunications network is to handle the data. The header is part of the overhead in a data transmission protocol.For typical TCP/IP transmissions (most Internet traffic), the header is usually 40 bytes of each packet (20-byte TCP and 20-byte IP headers). Note TCP and IP headers can be larger than 20 bytes if "options" are enabled. ICMP headers (as in pings) are 28 bytes. UDP headers are 8 bytes. QUOTE
hop A hop is the trip a data packet takes from one router to another in a packet-switching network. On a routed TCP/IP network, such as the Internet, the hop count is kept in the packet header and used to detect routing loops (packets with excessive hop count are discarded). The hop count is an important metric in finding the shortest path between nodes, and can be more significant than their geographical separation. QUOTE
traceroute traceroute is a utility that records the route between your computer and a destination computer on the Internet. It measures the time it takes to reach each node (specific gateway computer at each hop) needed to make the connection.Traceroute is a handy tool both for understanding where problems are in the network (packet loss, high latency) and for getting a detailed sense of the network itself. The traceroute utility sends 3 ICMP packets to each node, increasing the "time to live" value of packets and seeing how far they get until they reach the given destination; thus, a trail of hosts passed through and time to them is built up.The traceroute utility comes included with most current operating systems as part of the TCP/IP package. In Windows, traceroute can be used from the Command Prompt, by typing: tracert www.speedguide.net good! good! QUOTE
throughputThroughput (or transfer rate) in data transmission is the amount of data moved successfully from one place to another in a given time period.For data networks, throughput is usually measured in number of bits per second (bps) that are transmitted, also quoted as Kilobits per second (Kbps) or Megabits per second (Mbps). QUOTE
latencyLatency, or simply delay is an expression of how much time it takes for a packet of data to get from one designated point to another. Latency is often measured by sending a packet that is returned to the sender and the round-trip time (RTT) is considered the latency. QUOTE
3.1 IP numbers belong to Interfaces - NOT hosts! First of all, let's clear up a basic cause of misunderstanding - IP numbers are not assigned to hosts. IP numbers are assigned to network interfaces on hosts. Eh - what's that? Whilst many (if not most) computers on an IP network will possess a single network interface (and have a single IP number as a consequence), this is not the only way things happen. Computers and other devices can have several (if not many) network interfaces - and each interface has its own IP number. So a device with 6 active interfaces (such as a router) will have 6 IP numbers - one for each interface to each network to which it is connected. The reason for this becomes clear when we look at an IP network! Despite this, most people refer to host addresses when referring to an IP number. Just remember, this is simply shorthand for the IP number of this particular interface on this host. Many (if not the majority) of devices on the Internet have only a single interface and thus a single IP number. OK,JUST 哔咧. UP... UP...
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