Information Technology Reference
In-Depth Information
Figure 3-7
Baseline BGP Convergence Statistics
Base Line Convergence
350
500
450
300
400
250
350
300
200
250
150
200
150
100
100
50
50
0
0
70, 000
80, 000
90,000
100,000
110,000
120,000
130,000
140, 000
158
178
195
227
244
254
277
315
Convergence Times
202
264
257
264
252
464
366
467
Input Drop Count
Prefix Count
Convergence Times
Input Drop Count
The BGP convergence time is reasonably linear. The network takes 158 seconds to converge
with 70,000 prefixes and 315 seconds with 140,000 prefixes. The input drop count is rea-
sonably low; however, note that it remains low until the 120,000 prefix mark, at which point
it increases dramatically. This can be accounted for by TCP's engaging its congestion-
management mechanisms. The initial packet loss causes TCP to back off. The reduction in
packet loss causes TCP to increase its rate again, causing further loss.
Peer Group Benefits
The peer group feature is the first deployed. As stated in the section “Peer Groups,” this
feature is the foundation for all performance tuning. The rest of the testing performed
includes BGP peer groups.
The BGP feature status is as follows:
•
Peer groups are enabled.
•
Path MTU Discovery is disabled (TCP MSS 536).
•
The input hold queue is 75.
•
Update packing is not supported.
