Chapter 11 Firewall screens
191
Nortel Business Secure Router 252 Configuration — Basics
The Business Secure Router measures both the total number of existing half-open
sessions and the rate of session establishment attempts. Both TCP and UDP
half-open sessions are counted in the total number and rate measurements.
Measurements are made once a minute.
After the number of existing half-open sessions rises above a threshold
(
max-incomplete high
), the Business Secure Router starts deleting half-open
sessions as required to accommodate new connection requests. The Business
Secure Router continues to delete half-open requests as necessary, until the
number of existing half-open sessions drops below another threshold
(
max-incomplete low
).
After the rate of new connection attempts rises above a threshold (
one-minute
high
), the Business Secure Router starts deleting half-open sessions to
accommodate new connection requests as required. The Business Secure Router
continues to delete half-open sessions, as necessary, until the rate of new
connection attempts drops below another threshold (
one-minute low
). The rate is
the number of new attempts detected in the last one minute sample period.
TCP maximum incomplete and blocking period
An unusually high number of half-open sessions with the same destination host
address indicates that a Denial of Service attack is being launched against the
host.
Whenever the number of half-open sessions with the same destination host
address rises above a threshold (
TCP Maximum Incomplete
), the Business
Secure Router starts deleting half-open sessions according to one of the following
methods:
•
If the
Blocking Period
timeout is 0 (the default), the Business Secure Router
deletes the oldest existing half-open session for the host for every new
connection request to the host. This ensures that the number of half-open
sessions to a given host never exceeds the threshold.
•
If the
Blocking Period
timeout is greater than 0, the Business Secure Router
blocks all new connection requests to the host giving the server time to handle
the present connections. The Business Secure Router continues to block all
new connection requests until the
Blocking Period
expires.
Содержание BSR252
Страница 28: ...28 Tables NN47923 500 ...
Страница 44: ...44 Chapter 1 Getting to know your Business Secure Router NN47923 500 ...
Страница 52: ...52 Chapter 2 Introducing the WebGUI NN47923 500 ...
Страница 70: ...70 Chapter 3 Wizard setup NN47923 500 ...
Страница 91: ...Chapter 5 System screens 91 Nortel Business Secure Router 252 Configuration Basics Figure 20 Time and Date ...
Страница 96: ...96 Chapter 5 System screens NN47923 500 ...
Страница 100: ...100 Chapter 6 LAN screens NN47923 500 Configuring IP Click LAN to open the IP screen Figure 22 LAN IP ...
Страница 111: ...Chapter 7 WAN screens 111 Nortel Business Secure Router 252 Configuration Basics Figure 26 WAN WAN ISP ...
Страница 114: ...114 Chapter 7 WAN screens NN47923 500 Figure 27 WAN IP ...
Страница 120: ...120 Chapter 7 WAN screens NN47923 500 Figure 31 Dial Backup Setup ...
Страница 128: ...128 Chapter 7 WAN screens NN47923 500 ...
Страница 152: ...152 Chapter 9 Static Route screens NN47923 500 ...
Страница 194: ...194 Chapter 11 Firewall screens NN47923 500 ...
Страница 210: ...210 Chapter 13 VPN NN47923 500 Figure 67 Summary IP Policies ...
Страница 222: ...222 Chapter 13 VPN NN47923 500 Figure 71 VPN Branch Office rule setup ...
Страница 231: ...Chapter 13 VPN 231 Nortel Business Secure Router 252 Configuration Basics Figure 72 VPN Branch Office IP Policy ...
Страница 249: ...Chapter 13 VPN 249 Nortel Business Secure Router 252 Configuration Basics Figure 78 VPN Client Termination ...
Страница 256: ...256 Chapter 13 VPN NN47923 500 Figure 81 VPN Client Termination advanced ...
Страница 260: ...260 Chapter 13 VPN NN47923 500 ...
Страница 264: ...264 Chapter 14 Certificates NN47923 500 Figure 83 My Certificates ...
Страница 270: ...270 Chapter 14 Certificates NN47923 500 Figure 85 My Certificate create ...
Страница 274: ...274 Chapter 14 Certificates NN47923 500 Figure 86 My Certificate details ...
Страница 282: ...282 Chapter 14 Certificates NN47923 500 Figure 89 Trusted CA details ...
Страница 298: ...298 Chapter 14 Certificates NN47923 500 ...
Страница 316: ...316 Chapter 16 IEEE 802 1x NN47923 500 ...
Страница 320: ...320 Chapter 17 Authentication server NN47923 500 Figure 106 Local User database edit ...
Страница 328: ...328 Chapter 17 Authentication server NN47923 500 ...
Страница 376: ...376 Chapter 20 Logs Screens NN47923 500 Figure 150 Log settings ...
Страница 386: ...386 Chapter 20 Logs Screens NN47923 500 ...
Страница 392: ...392 Chapter 21 Call scheduling screens NN47923 500 Figure 157 Applying Schedule Sets to a remote node ...
Страница 393: ...Chapter 21 Call scheduling screens 393 Nortel Business Secure Router 252 Configuration Basics ...
Страница 394: ...394 Chapter 21 Call scheduling screens NN47923 500 ...
Страница 409: ...Chapter 22 Maintenance 409 Nortel Business Secure Router 252 Configuration Basics Figure 170 Restart screen ...
Страница 410: ...410 Chapter 22 Maintenance NN47923 500 ...
Страница 430: ...430 Appendix A Troubleshooting NN47923 500 ...