stomers may rely on the PPDN, or they may arrange their own transport. Having their own packet pipes gives private data network customers direct control over the performance of their networks. Sharing their IP packet traffic with the Inter- net leaves them out of control of their own data. Not only does the public network leave them at the mercy of PPDN delays, but it means that their data may be intercepted easily third parties. 3 They will have their own QoS standard and may even have an SLA with the wireless service provider. The SLA for data service performance defines the amount of data delay that the pri- vate packet links can have. From the delay and traffic estimates, we can do a traffic en- gineering exercise to figure out the capacity requirement for the packet pipe. If the private network is concentrated in a cell, then one base station may serve entire private data network for a customer. Then we may decide to have the dedi- cated packet pipe for that customer's network go directly from the base station to the customer. 37.3 Conclusion Careful planning of the transport from each MSC to other MSCs and to various termi- nation points on the PSTN, the PPDN, and private data services guarantees a low blocking rate while keeping costs reasonable. In Chap. 38 we will turn our attention to unusual circumstances that require special planning, completing Part 6. The air interface is hardly private, but it is difficult to intercept data for a particular user who may be anywhere in the coverage area. Encryption helps, but customers may not even want their competitors to know how much data traffic they are sending. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. MSC Transport Planning Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright© 2004 The McGraw-Hill Companies. All rights reserved. A