implicit null and explicit null

[amms68958]

Hi,

1) If a router receives a label of 0,what is it supposed to do..?

label poppoing or swapping th label with 0.

2) If a router receives the label of 3,whether it pops the label or swap the incoming label with the value of 3..?

Thansk

[olorunloba]

1. If a router recieves a label value of 0, this implies the explicit null label. The router will swap the top label for label 0 and forward the packet. The next LSR will pop the packet.

2. If a label of 3 is recieved, this implies the implicit null label. The router in this case will pop the top label and forward the remaining. If there was only one label in the stack, it will forward the IP packet, else the labelled packet with the topmost label removed.

Check this link, and RFC 3032 for more explanation

http://www.cisco.com/en/US/tech/tk436/tk428/technologies_q_and_a_item09186a00800949e5.shtml#q13