TCP/IP Animation , IP communication
IP communicationIP (Internet Protocol) is a rule for sending data. There are 2 kinds, one is IPv4 and the other is IPv6. IPv4 is an old style but it is still prevail. IPv6 is a new style for compensating the lack of IPv4, but it hasn't replaced IPv4 yet. They are coexisting.Before the data is conveyed, it is divided into small pieces called packets. And IP header is added to the all packets. Then the packets are transferred according to contents of the header.1. IPv4 headerDestination and Source IP address, 'Time to Live' and 'Checksum' is mainly recorded. 'Time to Live' means existence time. It decreases as the packet passes a device. And if the number comes to 0, the packet extinguishes.2. IPv6 headerIPv6 header is similar to IPv4 header. 'Hop limit' replaces 'Time to Live'.3. Routing tableRouter refers to its routing table when it receives data and need to relay it. Global IP address of Many LAN and that of the next router in order to progress to each LAN is recorded in the table. The next router is decided considering the shortest way to those LAN.
IPv4Standard IPv4 communication1.PC : Requests website data with IPv4.2.A's Router :Source IP Address is changed from private to global at this router with NAT.3.A's Router :This global IP address was assigned by ISP 'B' corporation dynamically.4.A's Router :Searches for the route to the destination with its routing table.5.A's Router :Found the next router.6.A's Router :Sends the data to the next.7.B's Router :This router of the ISP has many route information in its routing table.8.B's Router :Found the next router.9.B's Router :Sends the data to the next.10.C's Router :Searches for the route to the destination with its routing table.11.C's Router :Found the next router.12.C's Router :Sends the data to the next.13.D's Router :This router of the ISP has many route information in its routing table.14.D's Router :Finds the next router among the customers of the ISP.15.D's Router :Sends the data to the next.16.E's Router :Destination IP Address is changed from fixed global to fixed private at this router with static NAT.17.E's Router :Sends the data to the destination.18.Server : Gets the request.19.Server : Sends website data with IPv4.20.E's Router :Source IP Address is changed from fixed private to fixed global at this router with static NAT.21.E's Router :Searches for the route to the destination with its routing table.22.E's Router :Found the next router.23.E's Router :Sends the data to the next.24.D's Router :This router of the ISP has many route information in its routing table.25.D's Router :Found the next router.26.D's Router :Sends the data to the next.27.C's Router :Searches for the route to the destination with its routing table.28.C's Router :Found the next router.29.C's Router :Sends the data to the next.30.B's Router :This router of the ISP has many route information in its routing table.31.B's Router :Finds the next router among the customers of the ISP.32.B's Router :Sends the data to the next.33.A's Router :Destination IP Address is changed from global to private at this router with NAT.34.A's Router :Sends the data to the destination.35.PC : Got the website data.IPv4 loop troubleLoop trouble occurs during IPv4 communication1.Server : Sends website data with IPv4.2.E's Router :Source IP Address is changed from fixed private to fixed global at this router with static NAT.3.E's Router :Searches for the route to the destination with its routing table.4.E's Router :Found the next router.5.E's Router :Sends the data to the next.6.D's Router :This router of the ISP has many route information in its routing table.7.D's Router :Found the next router.8.D's Router :Sends the data to the next.9.C's Router :Searches for the route to the destination with its routing table.10.C's Router :The routing table is incorrect.11.C's Router :Found the next router.12.C's Router :Sends the data to the next.13.C's Router :The data loops, and 'Time to live' count decreases each arrival to a router.14.D's Router :When 'Time to live' count comes to 0, the data vanishes.15.D's Router :This affair is informed to the source machine with ICMP.16.Server : Receives ICMP message type 11 which means 'Time Exceeded'.17.Server : But no action for this trouble executes at IP protocol.18.Server : TCP will try to resolve this later by sending the same packets again because of no ACK return.IPv4 unreachable troubleUnreachable trouble occurs during IPv4 communication.1.Server : Sends website data with IPv4.2.E's Router :Source IP Address is changed from fixed private to fixed global at this router with static NAT.3.E's Router :Searches for the route to the destination with its routing table.4.E's Router :Found the next router.5.E's Router :Sends the data to the next.6.D's Router :No answer and packets vanishes. Power of the router is off by trouble.7.E's Router :Sends the data again.8.D's Router :No answer and packets vanishes. Power of the router is off by trouble.9.E's Router :Sends the data again.10.E's Router :Unreachable.This affair is informed to the source machine with ICMP.11.Server : Receives ICMP message type 3 which means 'Destination Unreachable'.12.Server : But no action for this trouble executes at IP protocol.13.Server : TCP will try to resolve this later by sending the same packets again because of no ACK return.IPv6Standard IPv6 communication1.PC : Requests website data with IPv6.2.PC : Sends request as it is because the next router supports IPv6.3.A's Router :Source IP Address isn't changed in case of using IPv6. And private IP address isn't be used.4.A's Router :Searches for the route to the destination with its routing table.5.A's Router :Found the next router.6.A's Router :Sends the data to the next as it is.7.B's Router :Searches for the route to the destination with its routing table.8.B's Router :Finds the next router beyond a router which doesn't support IPv6.9.B's Router :Sends the data using IP tunneling.10.D's Router :This router of the ISP has many route information in its routing table.11.D's Router :Finds the next router among the customers of the ISP.12.D's Router :Sends the data to the next.13.E's Router :Destination IP Address isn't changed in case of using IPv6.14.E's Router :Sends the data to the destination.15.Server : Gets the request.16.Server : Sends website data with IPv6.17.E's Router :Source IP Address isn't changed in case of using IPv6. And private IP address isn't be used.18.E's Router :Searches for the route to the destination with its routing table.19.E's Router :Found the next router.20.E's Router :Sends the data to the next.21.D's Router :Searches for the route to the destination with its routing table.22.D's Router :Finds the next router beyond a router which doesn't support IPv6.23.D's Router :Sends the data using IP tunneling.24.B's Router :This router of the ISP has many route information in its routing table.25.B's Router :Finds the next router among the customers of the ISP.26.B's Router :Sends the data to the next.27.A's Router :Destination IP Address isn't changed in case of using IPv6.28.A's Router :Sends the data to the destination.29.PC : Got the website data.IPv6 loop troubleLoop trouble occurs during IPv6 communication.1.Server : Sends website data with IPv6.2.E's Router :Source IP Address isn't changed in case of using IPv6. And private IP address isn't be used.3.E's Router :Searches for the route to the destination with its routing table.4.E's Router :Found the next router.5.E's Router :Sends the data to the next.6.D's Router :Searches for the route to the destination with its routing table.7.D's Router :Finds the next router beyond a router which doesn't support IPv6.8.D's Router :Sends the data using IP tunneling.9.B's Router :Searches for the route to the destination with its routing table.10.B's Router :The routing table is incorrect.11.B's Router :Found the next router.12.B's Router :Sends the data to the next.13.B's Router :The data loops, and Hop count decreases each arrival to a router.14.D's Router :When Hop Limit count comes to 0,the data vanishes.15.D's Router :This affair is informed to the source machine with ICMPv6.16.Server : Receives ICMPv6 message type 3 which means 'Time Exceeded'.17.Server : But no action for this trouble executes at IP protocol.18.Server : TCP will try to resolve this later by sending the same packets again because of no ACK return.IPv6 unreachable troubleUnreachable trouble occurs during IPv6 communication.1.Server : Sends website data with IPv6.2.E's Router :Source IP Address isn't changed in case of using IPv6. And private IP address isn't be used.3.E's Router :Searches for the route to the destination with its routing table.4.E's Router :Found the next router.5.E's Router :Sends the data to the next.6.D's Router :No answer and packets vanishes. Power of the router is off by trouble.7.E's Router :Sends the data again.8.D's Router :No answer and packets vanishes. Power of the router is off by trouble.9.E's Router :Sends the data again.10.E's Router :Unreachable.This affair is informed to the source machine with ICMPv6.11.Server : Receives ICMPv6 message type 1 which means 'Destination Unreachable'.12.Server : But no action for this trouble executes at IP protocol.13.Server : TCP will try to resolve this later by sending the same packets again because of no ACK return.
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