The latest from Telecom-Funda
| Ericsson Sues ZTE Over IPR Theft | Top |
| That Packet Has More IP Addresses Than I Can Count - Almost | Top |
| How many IP addresses does an IP packet have when it is sent between two devices? In a simple world only two, i.e. one for the destination and one of the source. The fun thing is how often that changes between source and destination due to all the tunneling and NATing applied. Let me give you an example of a typical setup of mine, a netbook connected via a Wifi / 3G bridge with a VPN tunnel established: Leg 1: Netbook - WiFi / 3G bridge As the VPN is established an IP packet is tunneled over IP. Thus there are 2 IP addresses to identify me as the source and two IP addresses for the destination: IP-1: IP address given by the Wifi bridge to the netbook IP-2: IP address of the VPN remote endpoint Inside the VPN tunnel: IP-3: IP address given by the VPN service to the tunnel end point (i.e. netbook) IP-4: IP address of the destination (e.g. the web server) Leg 2: Wi-Fi / 3G bridge to Mobile Network Gateway (GGSN) IP-5: IP address given to the WiFi bridge from the GGSN (NAT) IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- Leg 3: GGSN to VPN remote endpoint IP-6: IP address of the GGSN after NAT translation IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- Leg 4: VPN remote end point to web server IP-7: IP address of the VPN remote endpoint after NAT translation IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- Leg 1 to 4 are not the full story, there's also tunneling performed in the wireless network: Tunneling between SGSN and GGSN User data packets are tunneld over IP in the wireless core network. Here the packet looks like this: IP-7 SGSN network internal IP address IP-8 GGSN network internal IP address User data packet: IP-5: -unchanged- IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- Base Station to RNC While in the past the 3G radio access network was based on ATM, it is more and more replaced with Ethernet and IP for routing. This gives the packet another two IP addresses in this part of the network: IP-9 Base station network internal IP address IP-10 RNC network internal IP address User data packet: IP-5: -unchanged- IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- RNC to core network IP address No, we are not finished yet, the interface between RNC and SGSN is also based on IP these days and again tunneling is applied: IP-11 RNC network internal IP address on core network bound interface IP-12 SGSN network internal IP address on RAN bound interface User data packet: IP-5: -unchanged- IP-2: -unchanged- Inside the VPN tunnel: IP-3: -unchanged- IP-4: -unchanged- 12 different IP addresses are used in the course of transfering a packet between source and destination! WOW! | |
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