Enterasys Networks ANG-1100 Generic Routing Encapsulation GRE, Internet Service Provider ISP

Appendix A

Glossary

Generic Routing Encapsulation (GRE)

Tunneling protocol developed by Cisco that can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link over the Internet. For PPTP, GRE is used to encapsulate PPP data packets within an IP packet (IP packet headers contain address information necessary for routing, while PPP packets do not).

Internet Service Provider (ISP)

A vendor who provides direct access to the Internet. ISPs bill users for the amount of time they are connected, and may also offer additional services such as Web site hosting, E-mail, or news group readers. Remote users reach the ISP by dialing into an ISP POP with a computer, modem, and phone line, or over a dedicated circuit (such as a cable modem connection).

IP

Abbreviation of Internet Protocol, pronounced as two separate letters. IP specifies the format of packets, also called datagrams, and the addressing scheme. Most networks combine IP with a higher-level protocol called Transport Control Protocol (TCP/IP), which establishes a virtual connection between a destination and a source.

IP Address

An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 172.16.4.14 could be an IP address.

IP Security Protocol (IPSec)

Short for IPSecurity, a set of protocols developed to support secure exchange of packets at the IP layer.

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