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MPLS Extensions to ICMP

MPLS Extensions to ICMP. Ron Bonica Der-Hwa Gan Dan Tappan. Plain Old ICMP (RFC 792). When a router receives an IP datagram that it can’t forward, it sends an ICMP message to the datagram’s originator The ICMP message indicates why the datagram couldn’t be delivered

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MPLS Extensions to ICMP

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  1. MPLS Extensions to ICMP Ron Bonica Der-Hwa Gan Dan Tappan

  2. Plain Old ICMP (RFC 792) • When a router receives an IP datagram that it can’t forward, it sends an ICMP message to the datagram’s originator • The ICMP message indicates why the datagram couldn’t be delivered • E.g., Time Expired, Destination Unreachable • The ICMP message also contains the IP header and leading 8 octets of the original datagram • RFC 1812 extends this to “as many bytes as possible”

  3. ICMP Post MPLS (RFC 3032) • When an LSR receives an MPLS encapsulated datagram that it can’t deliver • It removes entire MPLS labels stack • It sends an ICMP message to datagram’s originator • The ICMP message indicates why the datagram couldn’t be delivered (e.g., time expired, destination unreachable) • The ICMP message also contains the IP header and leading 8 octets of the original datagram • RFC 1812 extends this to “as many bytes as possible”

  4. ICMP Post MPLS: Omissions • The ICMP message contains no information regarding the MPLS stack that encapsulated the datagram when it arrived at the LSR • This is a significant omission because: • The LSR tried to forward the datagram based upon that label stack • Resulting ICMP message may be confusing

  5. Confusing ICMP Messages • ICMP Destination Unreachable • Message contains IP header of original datagram • Router sending ICMP message has an IP route to the original datagram’s destination • Original datagram couldn’t be delivered because MPLS forwarding path was broken • ICMP Time Expired • Message contains IP header of original datagram • TTL value in IP header is greater than 1 • TTL expired on MPLS header. ICMP Message contains IP header of original datagram

  6. Proposal • Fix “Final Field” of ICMP message (IP header + leading payload bytes) to 128 bytes (0 padded). • Need to do this because it lacks a length attribute • Append extensions to that • Common Extension Header • Multiple Objects that share a common object header format • Currently defined Objects • MPLS Label Stack • Extended Payload Bytes (payload bytes 129+)

  7. TRACEROUTE: An Additional Benefit > traceroute 100.100.6.1 traceroute to 100.100.6.1 (100.100.6.1), 30 hops max, 40 byte packets 1 10.1.1.2 (10.1.1.2) 0.661 ms 0.618 ms 0.579 ms 2 10.1.12.2 (10.1.12.2) 0.861 ms 0.718 ms 0.679 ms MPLS Label=100048 Exp=0 TTL=1 S=1 3 10.1.24.2 (10.1.24.2) 0.822 ms 0.731 ms 0.708 ms MPLS Label=100016 Exp=0 TTL=1 S=1 4 10.100.6.1 (10.100.6.1) 0.961 ms 8.676 ms 0.875 ms

  8. Draft Status • Introduced in 1999 • Deployed since 2001 • Updated draft version available at www.bonica.org/docs/draft-ietf-mpls-icmp-04.txt • Resubmitted for your consideration

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