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D Capacities and Performance
Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000
412
Number of C-LANs
needed
The number of C-LAN circuit packs needed can be estimated as follows:
1 Calculate the C-LAN socket carried load, for c sockets, CLc
2 The number of C-LANs needed is:
# C-LANS = CL
c
/448 for infinite source, GOS of P001
# C-LANS = CL
c
/508 for “full availability.”
Assumptions
This formula assumes:
• 508 is the maximum number of simultaneous TCP/UDP connections per C-LAN.
• 448 is the average of Erlang B and Erlang C for GOS = P001 and 508
connections.
Example Internet Call Center
A DEFINITY call center with all incoming connections originating as H.323 DID
endpoints on the Internet. The customer requires 10,000 Busy Hour Calls (BHCs) be
carried, with a GOS of P001. The average call holding time is 100 seconds and the
codec is G723.1.
Problem
Calculate the DEFINITY resources required — the number of C-LANs and the
number of MedPros.
Solution
The average number of C-LAN sockets per call (c), for H.323 endpoints, is 2.
The number of audio streams per MedPro (a), for the G723.1 codec, is 22.
The endpoint carried load is:
10,000(
calls) x 1(CCS holding time per call)/36(CCS per Erlang) = 277.8 Erlangs.
From the MedPro table, 15 MedPro boards are required (rounding up).
Since there are 2 sockets per call (for H.323 endpoints), the socket carried load is
2x277.8 = 555.6 Erlangs.
Using the C-LAN formula, 555.6/448 = 2 C-LAN boards are required (rounding
up).