RFC 3031 Multiprotocol Label Switching Architecture Chapter 3

RFC 3031: Multiprotocol Label Switching Architecture Chapter 3. 27 – 3. 30 2005/07/14 (Thu) Shinichi Ishida

3. 27. Tunnels and Hierarchy Ru takes explicit action to deliver packet to Rd, even though Ru&Rd is not consecutive and Rd is not the ultimate destination => encapsulate the packet inside a network layer l Hop-by-Hop Routed Tunneled Packet follows the Hop-by-Hop path l Explicitly Routed Tunneled Packet travels over a path other than the Hop-by-Hop path

3. 27. 3. LSP Tunnels implemeting a tunnel as a LSP use label switching rather than network layer encapsulation the set of packets through the LSP tunnel constitutes a FEC, each LSR in the tunnel must assign a label to that FEC.

3. 27. 4. Hierarchy: LSP Tunnels within LSPs R 1 L IP R 4 R 2 L L IP IP R 3 R 22 R 21 R 23 L IP IP

3. 27. 5. (1/3) Label Distribition Peering and Hierarchy R 1 R 3 R 2 IGP neighbors R 21 when two LSRs are IGP neighbors > local label distibution peers not IGP neighbors > remote …

3. 27. 5. (2/3) Label Distribition Peering and Hierarchy u Explicit Peering distribute labels by sending messages which are addressed to the peer useful when the number of remote peer is small the number of higher level label bindings is large the remote peers are in distinct routing areas

3. 27. 5. (3/3) Label Distribition Peering and Hierarchy u Implicit Peering - encode a higher level label as an attribute of a lower label - distribute the lower leve label to local peers - local peers propagate the information to their local peers - continue till the information reaches the remote peer useful when the number of remote peers is large (not require n-square peering mesh)

3. 28. Label Distribution Protocol Transport label distribution protocol : establish and maintain the label binding Needs: reliability, in sequence, flow control use TCP as the underlying transport [MPLS-LDP] [MPLS-BGP]

3. 29. Why More than one Label Distribution Protocol ? ‘which’ label distribution protocol to use in ‘which’ circumstances ? # this architecture does NOT establish hard and fast rules for choosing point out some of the considerations in the following sections (3. 29. 1 – 3. 29. 3)

3. 29. 1. BGP and LDP desirable to bind labels to FECs idetified with routes to address prefixes If there is a standard, widely deployed routing algorithm -> label distribution is best achived by piggybacking on that ex) BGP a number of advantages RR: significant scalability

3. 29. 2. Labels for RSVP Flowspecs When RSVP is used for particular flows desirable to label the packets in those flows → RSVP filterspec: not need to be applied at each hop most efficient method of distributing labels = having RSVP distribute the labels as part of its path/reservation setup process ?

3. 29. 3. Labels for Explicitly Routed LSPs It is desirable for traffic engineering - to set up an explicitly routed path - to apply resource reservations along that path l two approaches start with existing protocol extend to support example 1 resource reservations explicit routing & label distribution MPLS-RSVPTUNNELS 2 label distribution explicit routing & resource reservations MPLS-CRLDP