A router R1 acts as a gateway to a VPN tunnel. At the other end of the tunnel is

Question

A router R1 acts as a gateway to a VPN tunnel. At the other end of the tunnel is another gateway R2. The two routers R1 and R2 are not directly connected to each other. Suppose that the Router R1 receives an IP datagram that needs to traverse the VPN tunnel. This implies that this incoming datagram needs to be encapsulated in another IP datagram before it can be sent over the VPN tunnel. However, R1's path MTU information indicates that this incoming datagram also requires fragmentation. Now, router R1 has two options to deal with this situation: Option 1: Encapsulate the original datagram and then subject the encapsulated packet to fragmentation. Option 2: Fragment the original datagram and then encapsulate each resulting fragment. Which of the two options should the router R1 opt for and why?

Explanation / Answer

Answer is as follows:

According to my opinion you have to choose the "Option 2".

You have to avoid the fragmentation after encapsulaton when you can do data sending over some hardware process. Where my mean Hardware process is the medium through which R1 and R2 are directly attached. Hardware encapulation can give you throughput of about 50 Mbps depending on the hardware but if you use fragmant after the encapsulatin you may loose 50 to 90 % of the throughput. This loos is because the fragmented packets are processed swithced for reassembling and handed to the hardware encryption to decryption. this loss of throughput can bring down the ardware encapsulation throughput to the performanc level of 1-2 Mbps.

So you should use the option 2 i.e. fragmaentation the original datagram and then encapsulate the each resulting fragmaentaion.In this IP routers can break the IP datagram into a series of fragment datagrams where each carries the portion of the data from the original datagram. A bit in the flag field of IP datagram as a fragment. where each IP datagram fragment assigned a different fragment offset. This is alll require to recieve to reassemble the packet.

if there is any query please ask in comments....

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.