Thread View: comp.std.internat
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Started by R.TRAUBEN
Wed, 06 Jan 1988 18:44
Still More Bit Rate Adaption Questions
Author: R.TRAUBEN
Date: Wed, 06 Jan 1988 18:44
Date: Wed, 06 Jan 1988 18:44
47 lines
2505 bytes
2505 bytes
Are I.46x, X.3, X.30, X.31 recommendations related? What precisely is the difference between a PAD and a rate adaption function? Is X.30 both a PAD and and rate adaption standard? Could someone please comment on the speculation made below: 1. It appears that a PAD buffers asynchronous traffic (e.g 1 character-at-a-time, start/stop rs232) into a synchronous, multiple character, packet burst using several criteria. Criteria appears to include: a) number of characters buffered, b) time elapsed since last packet transmitted, c) presence of special characters (e.g. return/break) X.28 appears to govern async RS232 to PAD conversion and X.29 appears to govern the PAD to sync X.21 conversion. X.3 appears to govern how the user sets PAD conversion parameters. 2. It appears that rate adaption is a function employed by a terminal adapter (e.g. RS232 to ISDN converter). The goal is to convert low speed outgoing synchronous multiple character, packet bursts (say 1200 bps) into higher speed intermediate outgoing synchronous multiple character packet bursts (say 8kbps). In ISDN, it appears that the rate adaption process is a 2 step approach. Step 1 converts the 1200 bps to an intermediate rate 8kbps by a bit replication process (4X plus 17-bit framing to construct a 8kbps 40-bit frame). Step 2 converts the intermediate rate from 8kbps to 64kbps. It is unclear to me where and how this happens (e.g. in the subcriber TA or within the ISDN phone network). The speed of the underlying intermediate rate is given to the ISDN net via the D-channel I451/Q931/L3 protocol so that the remote partner can recover the intermediate rate information. It is not clear to me how the remote partner can strip the 1200 bps information from the intermediate rate info. Has anyone waded thru this muck long enough to recommend a text besides the abstract I.460 and X.30 specs? I have both in my hands and am very confused by them. Thanks for your patience. Richard Trauben ATTIS HO, NJ ..ihnp4!houxv!rdt
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