HP X.25/9000 User's Guide HP-UX 11i v3 (5900-1523, August 2011)

Related Parameters
• Level 3 window size (W in formulas below) as configured in the x25config file.
• Level 3 packet size (P in formulas below) as configured in X.25 configuration file.
• Socket buffer size (B in formulas below) used in your applications (setsockopt() system
call). The default is 4 Kb.
Evaluation Formulas
The following formulas can be used to evaluate X.25 memory requirements:
Memory for each VC (MVC) in bytes:
MVC = (B x 3) + (2 x (W + 1) x P)
Total Memory (TM) for X.25 in bytes:
TM = sum (MVC) + Number of cards x 5120
NOTE: These figures are only for protocol and API requirements. You should also consider the
memory required by your applications.
Shortcut Method
Assuming B = P for all VCs, TM can be rounded to:
• If B < 512, TM = approx. (1,536 + (2 x W + 2) x B) x No. of VCs
• If B > or = 512, TM = approx. (2 x W + 5) x B x No. of VCs
The following table (in bytes/VC) provides a quick guide:
Buffer Size (B) = Packet Size (P) in bytesWindow (W)
size
409620481024512256128
28 K14 K7 K3.5 K2.5 K2 K1
36 K18 K9 K4.5 K3 K2.3 K2
44 K22 K11 K5.5 K3.5 K2.5 K3
52 K26 K13 K6.5 K4 K2.8 K4
60 K30 K15 K7.5 K4.5 K3 K5
68 K34 K17 K8.5 K5 K3.3 K6
76 K38 K19 K9.5 K5.5 K3.5 K7
A system has two X.25 cards configured as follows:
Card 1:
Window = 2
Packet size = 1024
Socket buffer size = 4096 (default)
200 VCs are used
Card 2:
Window = 4
Packet size = 128
Socket buffer size = 4096 (default)
400 VCs are used
Before you install the software 11