HP CommonIO Products Manuel d'utilisateur télécharger pdf (Page 21)

About the X.25 Product

Data link (L2) and Physical (L1) Levels

Chapter 1 21

Data link (L2) and Physical (L1) Levels

At the data link level (level 2), the X.25 link provides the LAP-B (Link

Access Procedure-Balanced) protocol. LAP-B is a data link protocol,

specified by the 1980 CCITT X.25 recommendations, that determines

frame exchange procedures.

At the physical level (level 1), the X.25 link provides support for X.21,

X.21bis, and V.35 interfaces (depending on your particular

communications hardware). These sets of recommendations define the

standards for X.25 at the physical level and apply specifically to

connections to a packet switching network. X.21bis (equivalent to V.24

and RS-232) is applicable to X.25 physical interfaces with transmission

speeds up to 64 kb/s. V.35, RS-449, X.21, and RS-530 supports

transmission speeds up to 2 Mb/s. Other standards may also be

supported as they become available.

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HP CommonIO Products Manuel d'utilisateur Page 21