
Chapter 11 Firewall screens
193
Nortel Business Secure Router 222 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 BSR222
Страница 28: ...28 Tables NN47922 500 ...
Страница 50: ...50 Chapter 2 Introducing the WebGUI NN47922 500 ...
Страница 66: ...66 Chapter 3 Wizard setup NN47922 500 ...
Страница 87: ...Chapter 5 System screens 87 Nortel Business Secure Router 222 Configuration Basics Figure 17 Time and Date ...
Страница 92: ...92 Chapter 5 System screens NN47922 500 ...
Страница 96: ...96 Chapter 6 LAN screens NN47922 500 Configuring IP Click LAN to open the IP screen Figure 19 LAN IP ...
Страница 104: ...104 Chapter 6 LAN screens NN47922 500 ...
Страница 115: ...Chapter 7 WAN screens 115 Nortel Business Secure Router 222 Configuration Basics Figure 27 WAN IP ...
Страница 123: ...Chapter 7 WAN screens 123 Nortel Business Secure Router 222 Configuration Basics Figure 32 Dial Backup Setup ...
Страница 154: ...154 Chapter 9 Static Route screens NN47922 500 ...
Страница 196: ...196 Chapter 11 Firewall screens NN47922 500 ...
Страница 212: ...212 Chapter 13 VPN NN47922 500 Figure 68 Summary IP Policies ...
Страница 223: ...Chapter 13 VPN 223 Nortel Business Secure Router 222 Configuration Basics Figure 72 VPN Branch Office rule setup ...
Страница 249: ...Chapter 13 VPN 249 Nortel Business Secure Router 222 Configuration Basics Figure 79 VPN Client Termination ...
Страница 256: ...256 Chapter 13 VPN NN47922 500 Figure 82 VPN Client Termination advanced ...
Страница 260: ...260 Chapter 13 VPN NN47922 500 ...
Страница 264: ...264 Chapter 14 Certificates NN47922 500 Figure 84 My Certificates ...
Страница 273: ...Chapter 14 Certificates 273 Nortel Business Secure Router 222 Configuration Basics Figure 87 My Certificate details ...
Страница 281: ...Chapter 14 Certificates 281 Nortel Business Secure Router 222 Configuration Basics Figure 90 Trusted CA details ...
Страница 290: ...290 Chapter 14 Certificates NN47922 500 Figure 95 Trusted remote host details ...
Страница 314: ...314 Chapter 16 IEEE 802 1x NN47922 500 ...
Страница 318: ...318 Chapter 17 Authentication server NN47922 500 Figure 107 Local User database edit ...
Страница 326: ...326 Chapter 17 Authentication server NN47922 500 ...
Страница 374: ...374 Chapter 20 Logs Screens NN47922 500 Figure 151 Log settings ...
Страница 384: ...384 Chapter 20 Logs Screens NN47922 500 ...
Страница 390: ...390 Chapter 21 Call scheduling screens NN47922 500 Figure 158 Applying Schedule Sets to a remote node ...
Страница 402: ...402 Chapter 22 Maintenance NN47922 500 Figure 170 Restart screen ...
Страница 422: ...422 Appendix A Troubleshooting NN47922 500 ...