Section 16.4. Summary

16.4. Summary

Our discussion of tunneling issues began with virtual private networks (VPNs), which are virtually used by a private-sector entity over a public network. Tunneling is an encapsulation of a packet data segment to move from one protocol to another protocol at the same or higher layer. An organization using a VPN uses a service provider's IP network and builds a private network and runs its own traffic.

Tunneling has two forms: remote-access tunneling, which is a user -to-LAN connection, and site-to-site tunneling, whereby an organization can connect multiple fixed sites over a public network. Employees who are located beyond their main campus can use point-to-point (PPP) connections to create tunnels through the Internet into the organization's resources. Both PPTP and L2TP depend on PPP to frame tunneled packets.

Multiprotocol label switching (MPLS) improves the overall performance of traditional IP routing, especially for the establishment of more effective VPNs. In MPLS, multiple labels can be combined in a packet to form a header used by an LSR for efficient tunneling. The Label Distribution Protocol (LDP) is a set of rules by which an LSR informs another LSR. The MPLS traffic engineering feature is an automated scheme for a control-signaling process and link-bandwidth assignment to improve the quality of network management.

Overlay networks create a virtual topology on top of an existing physical topology on a public network. Overlay networks are self-organized ; thus, if a node fails, the overlay network algorithm can provide solutions that let the network recreate an appropriate network structure.

The next chapter starts a new topic. We focus on multimedia networking, starting with the introductory concept of compression of digital voice and video .