el can be identified by the receiver. channel capacity The maximum data traffic that a channel can handle. CHAP (Challenge Handshake Authentication Protocol) A protocol that uses a three- way handshake to periodically verify the identity of the peer throughout the life of the connection. The server sends to the remote workstation a random token that is encrypted with the user's pass- word and sent back to the server. The server performs a lookup to see if it recognizes the password. If the values match, the authentication is acknowledged; if not, the connection is terminated. A dif- ferent token is provided each time a remote user dials in, which provides additional robustness. chirped-pulse WDM A Bell Labs system in which a specialized mode-locked laser rapidly emits very wide pulses of light. Because each part of a fiber interacts differently with varying fre- quencies of light, the result of chirped-pulse WDM is unequal dispersion. The pulse is stretched out when it enters the fiber, and data can be put on the discrete frequencies that emerge. CIDR (Classless Interdomain Routing) An IP addressing scheme replaces older system based on Classes A, B, and C. With CIDR, a single IP address can be used to designate CIR (committed information rate) many unique IP addresses. The CIDR addressing scheme is hierarchical. Large national and regional service providers are allocated large blocks of contiguous Internet addresses, which they then allocate to other smaller ISPs or directly to organizations. Networks can be divided into subnetworks, and networks can be combined into supernetworks, as long as they share a com- mon network prefix. CIR (committed information rate) The amount of bandwidth that a user can expect from a Frame Relay carrier on a particular virtual circuit. circuit The physical path that runs between two or more points that can be used for two-way communication or to perform another specific function. circuit grade The data-carrying capability of a circuit. The grades of circuit are broadband, voice, s