Ping: A utility to determine whether a specific IP address is accessible. It works by sending a packet to the specified address and waiting for a reply. PING is used primarily to troubleshoot Internet connections. There are many freeware and shareware Ping utilities available for personal computers. It is often believed that "Ping" is an abbreviation for Packet Internet Groper, but Ping's author has stated that the names comes from the sound that a sonar makes. ICMP: Short for Internet Control Message Protocol, an extension to the Internet Protocol (IP) defined by RFC 792. ICMP supports packets containing error, control, and informational messages. The PING command, for example, uses ICMP to test an Internet connection. Trace Route: A utility that traces a packet from your computer to an Internet host, showing how many hops the packet requires to reach the host and how long each hop takes. If you're visiting a Web site and pages are appearing slowly, you can use traceroute to figure out where the longest delays are occurring. The original traceroute is a UNIX utility, but nearly all platforms have something similar. Windows includes a traceroute utility called tracert. In Windows 95, you can run tracert by selecting Start->Run…, and then entering tracert followed by the domain name of the host. For example: tracert www.pcwebopedia.com Traceroute utilities work by sending packets with low time-to-live (TTL) fields. The TTL value specifies how many hops the packet is allowed before it is returned. When a packet can't reach its destination because the TTL value is too low, the last host returns the packet and identifies itself. By sending a series of packets and incrementing the TTL value with each successive packet, traceroute finds out who all the intermediary hosts are. Nslookup / Name Server Lookup: A utility used to query Internet domain name servers. An nslookup is usually used to find the IP address corresponding to a hostname. An nslookup may also be used to find other types of information such as CNAME - the canonical name for an alias; MINFO - mailbox or mail list information; MX - mail exchanger information; NS - the name server for the named zone; and SOA the domain's start-of-authority information. Whois: An Internet utility that returns information about a domain name or IP address. For example, if you enter a domain name such as microsoft.com, whois will return the name and address of the domain's owner (in this case, Microsoft Corporation).