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Voice over Multiprotocol Label switching
Challenges in IP network
 Shortest path is followed in IP network
 Load sharing is not possible
 Congestion is created in IP network
 Routing in network layer
 Processing is slow and delay is more
SOLUTION TO THE PROBLEM ?
MPLS
• Multi protocol label switching
• Reduces excessive delay
• Instead of shortest follows suitable path on the basis of constraint
• Reduce packet loss
• Provide TE
• Provide QOS and VPN networking
• How it work
• MPLS architecture
• LSR
• LER
• LSP
• LDP
• FEC
MPLS header
• MPLS operates by defining a label called shim header
• MPLS header is 32 bits
• MPLS operation
• label creation and distribution
• Table creation
• LSP creation
• Label insertion/lookup table
• Packet forwarding
• Traffic engineering TE
• Important factor for TE
• TE in MPLS
• Constraint based routing CBR
• Tunneling in MPLS
Label creation
• There are three method used in label creation,
1. Topology- based method
2. Request- based method
3. Traffic -based method
• Topology based method: uses normal processing of routing protocol(e.g. OSPF ,BGP)
• Request based method: uses processing of request based control traffic( such as RSVP)
• Traffic based method: uses the reception of packet to trigger the assignment and distribution of label
Label distribution
• The various schemes are used for label exchange are as ,
1. LDP-maps unicast IP destination into labels
2. RSVP,CR-LDP – used for traffic engineering and resource reservation
3. Protocol independent multicast(PIM)- is used for multicast state label mapping
4. BGP- for external labels (VPN)
Table creation
• On receipt of label binding each LSR creates entries in the LIB
• The table will specify the mapping between a label and an FEC
• Mapping b/w the I/p port and I/p label and o/p port and o/p label
• Table are updated whenever renegotiation of the label binding occurs.
LSP creation
• Label switch path are set by the signaling protocols
 LDP
 RSVP
• LSP is unidirectional
• In MPLS domain there exist number of LSPs that originate at ingress router and traverses one or more core LSRs and terminate at Egress router.

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