ait in line. How much business can this server support so that 90 percent of the time a new customer sees an available server? This means that the server is only busy 10 percent of the time. A demand of 10 percent of an erlang will keep one server busy 10 percent of the time. TABLE 23.1 Erlang-B Capacity Table Erlang-B capacity Lines P(B) = 0.01 P(B) = 0.02 P(B) = 0.05 P(B) = 0.10 11.47 11.54 13.50 10.44 11.49 13.39 15.55 12.03 13.18 15.25 17.61 16.12 17.50 19.99 22.83 20.34 21.93 24.80 28.11 24.64 26.43 29.68 33.43 29.01 31.00 34.60 38.79 33.43 35.61 39.55 44.17 37.90 40.26 44.53 49.56 46.95 49.64 54.57 60.40 56.11 59.13 64.67 71.29 65.36 68.69 74.82 82.20 74.68 78.31 85.01 93.15 84.06 87.97 95.24 104.11 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. Traffic Engineering for Voice and Data Capacity and Quality Principles Well, this is almost correct. Since the customers turned away are out of the system, we can raise the demand levels SO that the remaining 90 percent keeps the server busy 10 percent of the time. Solving the algebra tells us that a demand of one-ninth of erlang for one server has nine-tenths of it keeping the server busy one-tenth of the time. And the other one-tenth is the traffic turned away by the busy server. The same reasoning applies to 1, 2, and 5 percent blocking for a single server. The correction terms are smaller because fewer customers are being turned away, but the reasoning is the same. A single server at 5 percent blocking serves just a little over 0.05 erlang, not very efficient. Going to two servers improves our efficiency enormously. Picture two servers serving 0.2 erlang each. Ignoring the turn-away correction terms, we estimate that each of these servers has 20 percent blocking. If that 20 percent can overflow to the other server, then the only time a customer is blocked is when both servers are busy. Wit