92 CHAPTER 8: IP PERFORMANCE CONFIGURATIONthe system restarts the timer from receiving the last non-FIN packet. Theconnection is broken after the timer expires.■ Size of TCP receive/send bufferDisabling ICMP to SendError PacketsSending error packets is a major function of ICMP protocol. In case of networkabnormalities, ICMP packets are usually sent by the network or transport layerprotocols to notify corresponding devices so as to facilitate control andmanagement.By default, Switch 4210 Family support sending ICMP redirect and destinationunreachable packets.Although sending ICMP error packets facilitate control and management, it stillhas the following disadvantages:■ Sending a lot of ICMP packets will increase network traffic.■ If receiving a lot of malicious packets that cause it to send ICMP error packets,the device’s performance will be reduced.■ As the ICMP redirection function increases the routing table size of a host, thehost’s performance will be reduced if its routing table becomes very large.■ If a host sends malicious ICMP destination unreachable packets, end users maybe affected.You can disable the device from sending such ICMP error packets for reducingnetwork traffic and preventing malicious attacks.Table 52 Configure TCP attributesOperation Command RemarksEnter system view system-view -Configure TCP synwait timer’stimeout valuetcp timer syn-timeouttime-valueOptionalBy default, the timeout valueis 75 seconds.Configure TCP finwait timer’stimeout valuetcp timer fin-timeouttime-valueOptionalBy default, the timeout valueis 675 seconds.Configure the size of TCPreceive/send buffertcp window window-size OptionalBy default, the buffer is 8kilobytes.Table 53 Disable sending ICMP error packetsOperation Command RemarksEnter system view system-view -Disable sending ICMPredirectsundo icmp redirect send RequiredEnabled by defaultDisable sending ICMPdestination unreachablepacketsundo icmp unreach send RequiredEnabled by default
