Cabletron Systems CyberSWITCH CSX150 User Manual

Also see for CyberSWITCH CSX150: User guide Quick start guide

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USER’S GUIDE328 CyberSWITCHcompression enable/disable state based on this value when no value is delivered by the off-nodedatabase.You may later change a specific device’s enable/disable state.The per-device compression enable/disable state is only supported for connections using the PPPprotocol. The default value is enabled.STARTING PPP STAC-LZS SEQUENCE NUMBERDefault value is 1. When using PPP Compression with the STAC-LZS protocol, a sequencenumbering scheme can be used whose initial value is required to be 1 by the protocol specification.Some devices from other vendors do not start with 1. This results in a resynchronization sequenceon the first frame which is exchanged. When the user device fully supports the CCP protocol’sReset mechanism, this will only result in the minor inconvenience of a lost frame at the beginningof a session. However, if such a device’s resynchronization mechanism is to completely renegotiateCCP, this sequence will repeat infinitely.This option provides an escape mechanism to allow interworking with such devices by modifyingthe initial PPP STAC sequence number.The Starting PPP STAC Sequence Number is maintained for each device. The value which appearson this configuration screen provides the default value for the per-device value. When you add anew device to the on-node device table, that device’s starting sequence number option will beassigned the value which appears on this screen. You can then change this for each individualdevice. Or, if the device is authenticated via an off node server that does not deliver a value for thisconfiguration item, the device will be given its starting sequence number from the value on thismenuAs its name implies, this option only applies to connections which utilize the PPP protocol withSTAC-LZS compression and sequence numbers checking.COMPRESSION O PTIONS BACKGROUND I NFORMATIONThe system data compression capability allows the system to negotiate compression algorithmswith a remote device. This compression can be done using some proprietary bridging protocols andalso the PPP CCP protocol.After successfully negotiating compression, data is compressed by a peer and transmitted to thesystem. The system decompresses the data, processes the addressing information contained in thedevice data, and transmits the data as required. The converse is also true, the system can receivedata coming from a WAN or LAN, compresses the data before transmitting it to a peer. The neteffect is to increase effective interconnect bandwidth by decreasing transmission time. Ifnegotiation for compression fails, data is transmitted uncompressed.The compression algorithm implemented is STAC-LZS. This algorithm is used in all of STAC’s datacompression products. This software version is fully compatible with STAC’s data compressioncompressor chips including the multi-tasking features. STAC-LZS data compression is performedby replacing redundant strings in a data stream with shorter tokens. The STAC-LZS uses acompression history, or sliding window, as opposed to a structured dictionary. This allows greaterflexibility and a greater number of possible string comparisons during compression process. Thecompression history automatically discards old information as new information is processed. Boththe device and system must perform compression using the STAC-LZS data compression