MPLS Error Checking

CChN

Assuming IPv4 as the L3 protocol, if packets are label switched as they traverse the MPLS domain does that not mean that erroneous packets can be sent through the network undetected until they reach the destination? Since the IPv4 checksum wouldn't be calculated at each hop?

Sirsamon

I may be wrong here but i would say no.

As packets enter the MPLS edge router they are labeled if they match the defined interesting traffic, If not dropped.

once in the MPLS network the backbones will look at the label if no label then the packet is dropped.

except where PHP is running, then the exit edge router will recieve a normal IPv4 packet and do a route table lookup.

there a lot more going on in the backround, but i think this is the basics of it.

dtlokee

it really would depend on what exact type of errors had occured. Just because the L3 header checksum is not updated or used in the MPLS network does not mean that there is no for of checksum used. Many L2 datalinks will use some form of a CRC on the entire frame where the L3 IP header checksum is just that, a checksum of only the L3 header and nothing else (not the data or any other layer's header)