Connection alternatives

PPP can transmit datagrams over serial point-to-point links.

PPP enables interconnection of multiple vendor equipment and multiple protocols by standardizing point-to-point communications. The PPP data link layer uses High-level Data Link Control (HDLC)-like framing for encapsulating datagrams over both asynchronous and synchronous point-to-point telecommunication links.

While PPP supports a wide range of link types, Serial-Line Internet Protocol (SLIP) only supports asynchronous link types. SLIP is generally employed only for analog links. Local telephone companies offer traditional telecommunications services in an ascending scale of capabilities and cost. These services use existing telephone company voice network facilities between customer and the central office.

PPP links establish a physical connection between a local and remote host. Connected links provide dedicated bandwidth. They also come in a variety of data rates and protocols. With PPP links, you can choose from the following connection alternatives:

• Analog telephone lines
  The analog connection, which uses modems to carry data over leased or switched lines, sits at the bottom of the point-to-point scale.
• Digital services and DDS
  You can use digital service and Digital Data Services (DDS) with PPP.
• Switched-56
  When you do not need a full-time connection, you can save money by using switched digital service, which is generally called Switch-56 (SW56).
• Integrated Services Digital Network
  Integrated Services Digital Network (ISDN) provides switched end-to-end digital connectivity. Unlike other services, however, ISDN can carry both voice and data over the same connection.
• T1/E1 and fractional T1
  T1/E1 and fractional T1 are two kinds of valid connection alternatives.
• Frame relay
  Frame relay is a protocol for routing frames through the network based on the IP address field (data link connection identifier) in the frame and for managing the route or virtual connection.
• L2TP (tunneling) support for PPP connections
  Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol that extends PPP to support a link layer tunnel between a requesting L2TP client (L2TP Access Concentrator or LAC) and a target L2TP server endpoint (L2TP Network Server or LNS).
• PPPoE (DSL) support for PPP connections
  Digital subscriber line (DSL) refers to a class of technology used to obtain more bandwidth over existing copper telephone cabling running between a customer's premises and an ISP provider.