Configuring Tcp Attributes; Configuring To Send Special Ip Packets To Cpu; Enabling Forwarding Of Directed Broadcasts To A Directly Connected Network - 3Com 7757 Configuration Manual

132 C 16: IP P
HAPTER ERFORMANCE
Configuring TCP
Attributes
Configuring to Send
Special IP Packets to
CPU
Enabling Forwarding
of Directed Broadcasts
to a Directly
Connected Network
C
ONFIGURATION
Table 77 Configure TCP attributes
Operation
Enter system view
Configure timeout time for the
synwait timer in TCP
Configure timeout time for the
finwait timer in TCP
Configure the socket receiving
and sending buffer size of TCP
Usually the switch sends TTL timeout packets and unreachable packets to the CPU
in the process of forwarding IP packets. The CPU processes these special packets
after receiving them. Incorrect configuration and malicious attack will cause heavy
CPU load. You can perform the following configuration to configure not to send
corresponding packets to the CPU in order to ensure normal running.
Table 78 Configure to send special IP packets to CPU
Operation
Enter system view
Configure to send TTL
timeout packets and
unreachable packets to CPU
Broadcast packets include full-net broadcast packets and directed broadcast
packets. The destination IP address of a full-net broadcast packet is all 1s
(255.255.255.255). A directed broadcast packet is a packet whose destination IP
address is the network broadcast address of a subnet, but the source IP address is
not in the subnet. When a switch forwards a directed broadcast packet, it cannot
tell whether the packet is a broadcast packet if the switch is not connected with
the subnet.
If a directed broadcast packet reaches the destination network after being
forwarded by the switch, the switch will receive the broadcast packet, for the
switch also belongs to the subnet. Since the VLAN of the switch isolates the
broadcast domain, the switch will stop forwarding the packet to the network.
Using the commands, you can choose to forward the directed broadcast packet to
the directly connected network.
Command
system-view
tcp timer syn-timeout time-value
tcp timer fin-timeout time-value
tcp window window-size
Command
system-view
ip { ttl-expires | unreachables }
Description
-
Required
The default value is
75 seconds
Required
The default value is
675 seconds
Required
By default, the size
of the socket
receiving and
sending buffers is 8
KB
Description
-
Required
By default,
unreachable packets
are not sent to the
CPU, while TTL timeout
packets are sent to the
CPU