Cabletron Systems CSX200 CyberSWITCH Installation Manual

Also see for CSX200 CyberSWITCH: Setup guide User guide Configuration guide User guide

Contents

CSX200 Firmware SupportCSX200 Installation Guide2-7The ANSI standard defines a mechanism for the network to signal the existence of congestion,called Explicit Congestion Notification (ECN) bits. Frame Relay uses FECN (Forward ECN) andBECN (Backward ECN) bits to notify end user devices about network congestion. Although theFrame Relay Protocol does not respond to congestion, some higher layer protocols for end-userdevices may respond to ECNs by recognizing that delays have increased, or that frames have beendropped.Point-to-Point Protocol (PPP)PPP is a data link layer industry standard WAN protocol for transferring multi-protocol data trafficover point-to-point connections. With this protocol, options such as security, data compression,and network protocols can be negotiated over the connection. Data compression allows FrameRelay to negotiate compression over Frame Relay permanent virtual circuits (PVCs). Frame Relayis a packet-switching data communications protocol that statistically multiplexes many dataconversations over a single transmission link.The CSX200 supports synchronous PPP over an ISDN WAN port (WPIM-S/T). In Single LinkMode, PPP uses one ISDN B channel for data transmission. PPP runs over each ISDN B channelfor two separate conversations (split B channel). In Multi-Link Protocol mode, PPPsimultaneously sends and receives data over two ISDN B channels on the same connection tooptimize bandwidth usage. The STAC Electronics Stacker LZS Compression Protocol is supportedover PPP, providing up to 4:1 data compression.PAP and CHAP SecurityThe CSX200 supports the Password Authentication Protocol (PAP) and Challenge HandshakeAuthentication Protocol (CHAP) under PPP.PAP provides verification of passwords between devices using a two-way handshake. One device(peer) sends the system name and password to the other device (authenticator). Then theauthenticator checks the peer’s password against the configured remote peer’s password andreturns acknowledgment.CHAP is more secure than PAP as unencrypted passwords are not sent across the network. CHAPuses a 3-way handshake and supports full or half-duplex operation. In half-duplex operation, theauthenticator device challenges the peer device by generating a CHAP challenge. The challengecontains an MD5 algorithm with a random number that your encrypted password and systemname. The peer device then applies a one-way hash algorithm to the random number and returnsthis encrypted information along with the system name in the CHAP response. The authenticatorthen runs the same algorithm and compares the result with the expected value. This authenticationmethod depends upon a password or secret, known only to both ends locally.