180Appendix H: ASU background information
•CDPD XLIU terminates various protocols, such as LAPB and MDLP. XLIUs also store accounting information for data services.
•CDPD NIU stores and maintains subscriber routing and mobility information on the NIU software. The NIU contains the software that interfaces with the computing module (CM) for maintenance functions. The NIU also gives the XLIU channelized access to the
External routers
External routers allows the message transfer part (MTP) routing functionality to reside in the dedicated LIU7s instead of in the digital trunk controller 7 (DTC7). This configuration eliminates the necessity for the DTC7s to be informed of routing changes and thus significantly reduces the volume of messaging to the DTC7s.
Platforms
ASUs are supported on the following platforms:
•link peripheral processor (LPP)
•
•SuperNode SE link interface shelf (SNSE LIS)
Link peripheral processor
LPPs with a maximum of either 24 or 36 ASUs exist. However multi- application deployment is only supported on the
The LPP consists of two basic subsystems: the individual ASUs (LIU7s, EIUs, and so on) and the local message switch (LMS). Figure 44 shows a block diagram of the LPP. This figure illustrates the
The duplicated