Multiprotocol Label Switching Architecture," ftp://ftp.rfc-editor.org/in-notes/rfc3031.txt RFC 3031, January 2001.
MPLS Label Stack Encoding," ftp://ftp.rfc-editor.org/in-notes/rfc3032.txt RFC 3032, January 2001
Requirements for Traffic Engineering over MPLS," RFC 2702, September 1999
QoS Routing Mechanisms and OSPF Extensions," RFC 2676, August 1999.
BGP/MPLS VPNs, RFC 2547, March 1999
A Core MPLS IP VPN Architecture , RFC2917, September 2000
Tuesday, August 3, 2010
MPLS LABEL
MPLS uses a 32 bit header/label that contains the following information
20 Bit label :It’s a no. which is locally significant and assigned locally by router to FEC.
3 Bit experimental field : These three bits are known as experimental bits. This three bits is used for MPLS QOS purpose.
1 Bit bottom of stack indicator: The bit indicates which is last label in stack before IP header. Last label entry is 1 and others are 0.
8 Bit TTL field : This field has same function as IP header for Loop prevention in cloud.
MPLS label is inserted in between layer 2 and layer 3.
Watch in action -
MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (Data Link Layer) and Layer 3 (Network Layer), and thus is often referred to as a "Layer 2.5" protocol. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, Frame relay and Ethernet frames.
*Note: Figures are from Cisco website
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