MPLS, Multi-Protocol Label Switching

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: PPP, TCP/IP.
Protocol type:Network layer protocol.
Ethertypes: 0x8847 (unicast).
0x8848 (multicast).
PPP protocol:0x281, 0x283.
Working groups: ccamp, Common Control and Measurement Plane.
mpls, Multiprotocol Label Switching.
tewg, Internet Traffic Engineering.
IANA: MPLS parameters.
MPLS Pseudowire Types Registry.

RFC 3469:

MPLS integrates the label swapping forwarding paradigm with network layer routing. To deliver reliable service, MPLS requires a set of procedures to provide protection of the traffic carried on different paths. This requires that the LSRs support fault detection, fault notification, and fault recovery mechanisms, and that MPLS signaling support the configuration of recovery.

Label entry. 32 bits.
(RFC 3031) A short fixed length physically contiguous identifier which is used to identify a FEC, usually of local significance.

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Label TC S TTL

Label. 20 bits.

TC, Traffic class. 3 bits.
Renamed from Exp, experimental in RFC 5462.

S, bottom of stack. 1 bit.
Set to one for the last entry in the label stack (i.e., for the bottom of the stack) and cleared to zero for all other label stack entries.

TTL, Time to Live. 8 bits.

MPLS Pseudowire types.

0x0001Frame Relay DLCI (Martini Mode).RFC 4619
0x0002ATM AAL5 SDU VCC transport. 
0x0003ATM transparent cell transport.RFC 4717
0x0004Ethernet Tagged Mode. RFC 4448
0x0005Ethernet. RFC 4448
0x0006HDLC.RFC 4618
0x0007 PPP.RFC 4618
0x0008SONET/SDH Circuit Emulation Service Over MPLS Encapsulation.RFC 5143
0x0009ATM n-to-one VCC cell transport.RFC 4717
0x000AATM n-to-one VPC cell transport.RFC 4717
0x000BIP Layer2 Transport.RFC 3032
0x000CATM one-to-one VCC Cell Mode.RFC 4717
0x000DATM one-to-one VPC Cell Mode.RFC 4717
0x000EATM AAL5 PDU VCC transport.RFC 4717
0x000FFrame-Relay Port mode.RFC 4619
0x0010SONET/SDH Circuit Emulation over Packet.RFC 4842
0x0011Structure-agnostic E1 over Packet.RFC 4553
0x0012Structure-agnostic T1 (DS1) over Packet.RFC 4553
0x0013Structure-agnostic E3 over Packet.RFC 4553
0x0014Structure-agnostic T3 (DS3) over Packet.RFC 4553
0x0015CESoPSN basic mode.RFC 5086
0x0016TDMoIP AAL1 Mode.RFC 5087
0x0017CESoPSN TDM with CAS.RFC 5086
0x0018TDMoIP AAL2 Mode.RFC 5087
0x0019Frame Relay DLCI.RFC 4619
0x001AROHC Transport Header-compressed Packets.RFC 4901, RFC 5795
0x001BECRTP Transport Header-compressed Packets.RFC 3545, RFC 4901
0x001CIPHC Transport Header-compressed Packets.RFC 2507, RFC 4901
0x001DcRTP Transport Header-compressed Packets.RFC 2508, RFC 4901
0x001EATM VP Virtual Trunk. 
0x001FFC Port Mode.RFC 6307
0x7FFFWildcard.RFC 4863


FEC, Forwarding Equivalence Class.
(RFC 3031) A group of IP packets which are forwarded in the same manner (e.g., over the same path, with the same forwarding treatment).

frame merge.
(RFC 3031) Label merging, when it is applied to operation over frame based media, so that the potential problem of cell interleave is not an issue.

GMPLS, Generalized Multi-Protocol Label Switching.
(RFC 5339) Generalized MPLS (GMPLS) extends MPLS to handle multiple switching technologies. These include packet switching, layer-2 switching, TDM (Time Division Multiplexing) switching, wavelength switching, and fiber switching. The Interface Switching Capability (ISC) concept is introduced for these switching technologies and is designated as follows: PSC (Packet Switch Capable), L2SC (Layer-2 Switch Capable), TDM capable, LSC (Lambda Switch Capable), and FSC (Fiber Switch Capable). The representation, in a GMPLS control plane, of a switching technology domain is referred to as a region. A switching type describes the ability of a node to forward data of a particular data plane technology, and uniquely identifies a network region.

label merging.
(RFC 3031) The replacement of multiple incoming labels for a particular FEC with a single outgoing label.

label stack.
(RFC 3031) An ordered set of labels.

label swap.
(RFC 3031) The basic forwarding operation consisting of looking up an incoming label to determine the outgoing label, encapsulation, port, and other data handling information.

label swapping.
(RFC 3031) A forwarding paradigm allowing streamlined forwarding of data by using labels to identify classes of data packets which are treated indistinguishably when forwarding.

label switched hop.
(RFC 3031) The hop between two MPLS nodes, on which forwarding is done using labels.

loop detection.
(RFC 3031) A method of dealing with loops in which loops are allowed to be set up, and data may be transmitted over the loop, but the loop is later detected.

loop prevention.
(RFC 3031) A method of dealing with loops in which data is never transmitted over a loop.

LSP, label switched path.
(RFC 3031) The path through one or more LSRs at one level of the hierarchy followed by a packets in a particular FEC.

LSR, label switching router.
(RFC 3031) An MPLS node which is capable of forwarding native L3 packets.

merge point.
(RFC 3031) A node at which label merging is done.

MPLS domain.
(RFC 3031) A contiguous set of nodes which operate MPLS routing and forwarding and which are also in one Routing or Administrative Domain.

MPLS edge node.
(RFC 3031) An MPLS node that connects an MPLS domain with a node which is outside of the domain, either because it does not run MPLS, and/or because it is in a different domain. Note that if an LSR has a neighboring host which is not running MPLS, that that LSR is an MPLS edge node.

MPLS egress node.
(RFC 3031) An MPLS edge node in its role in handling traffic as it leaves an MPLS domain.

MPLS ingress node.
(RFC 3031) An MPLS edge node in its role in handling traffic as it enters an MPLS domain.

MPLS label.
(RFC 3031) A label which is carried in a packet header, and which represents the packet's FEC.

MPLS node.
(RFC 3031) A node which is running MPLS. An MPLS node will be aware of MPLS control protocols, will operate one or more layer 3 routing protocols, and will be capable of forwarding packets based on labels. An MPLS node may optionally be also capable of forwarding native layer 3 packets.

VC merge.
(RFC 3031) Label merging where the MPLS label is carried in the ATM VCI field (or combined VPI/VCI field), so as to allow multiple VCs to merge into one single VC.

VP merge.
(RFC 3031) Label merging where the MPLS label is carried din the ATM VPI field, so as to allow multiple VPs to be merged into one single VP. In this case two cells would have the same VCI value only if they originated from the same node. This allows cells from different sources to be distinguished via the VCI.

(RFC 3031) A label used in ATM networks to identify circuits.


[RFC 2702] Requirements for Traffic Engineering Over MPLS.

[RFC 2917] A Core MPLS IP VPN Architecture.

[RFC 3031] Multiprotocol Label Switching Architecture.

[RFC 3032] MPLS Label Stack Encoding.

[RFC 3034] Use of Label Switching on Frame Relay Networks Specification.

[RFC 3035] MPLS using LDP and ATM VC Switching.

[RFC 3036] LDP Specification.

[RFC 3063] MPLS Loop Prevention Mechanism.

[RFC 3107] Carrying Label Information in BGP-4.

[RFC 3270] Multi-Protocol Label Switching (MPLS) Support of Differentiated Services.

[RFC 3353] Overview of IP Multicast in a Multi-Protocol Label Switching (MPLS) Environment.

[RFC 3429] Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions.

[RFC 3443] Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks.

[RFC 3468] The Multiprotocol Label Switching (MPLS) Working Group decision on MPLS signaling protocols.

[RFC 3469] Framework for Multi-Protocol Label Switching (MPLS)-based Recovery.

[RFC 3471] Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description.

[RFC 3472] Generalized Multi-Protocol Label Switching (GMPLS) Signaling Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions.

[RFC 3473] Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions.

[RFC 3477] Signalling Unnumbered Links in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE).

[RFC 3564] Requirements for Support of Differentiated Services-aware MPLS Traffic Engineering.

[RFC 3811] Definitions of Textual Conventions (TCs) for Multiprotocol Label Switching (MPLS) Management.

[RFC 3812] Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Management Information Base (MIB).

[RFC 3813] Multiprotocol Label Switching (MPLS) Label Switching Router (LSR) Management Information Base (MIB).

[RFC 3814] Multiprotocol Label Switching (MPLS) Forwarding Equivalence Class To Next Hop Label Forwarding Entry (FEC-To-NHLFE) Management Information Base (MIB).

[RFC 3815] Definitions of Managed Objects for the Multiprotocol Label Switching (MPLS), Label Distribution Protocol (LDP).

[RFC 3919] Remote Network Monitoring (RMON) Protocol Identifiers for IPv6 and Multi Protocol Label Switching (MPLS).

[RFC 3945] Generalized Multi-Protocol Label Switching (GMPLS) Architecture.

[RFC 3946] Generalized Multi-Protocol Label Switching (GMPLS) Extensions for Synchronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH) Control.

[RFC 4003] GMPLS Signaling Procedure for Egress Control.

[RFC 4023] Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE).

[RFC 4105] Requirements for Inter-Area MPLS Traffic Engineering.

[RFC 4126] Max Allocation with Reservation Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering & Performance Comparisons.

[RFC 4127] Russian Dolls Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering.

[RFC 4139] Requirements for Generalized MPLS (GMPLS) Signaling Usage and Extensions for Automatically Switched Optical Network (ASON).

[RFC 4182] Removing a Restriction on the use of MPLS Explicit NULL.

[RFC 4201] Link Bundling in MPLS Traffic Engineering (TE).

[RFC 4202] Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS).

[RFC 4203] OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS).

[RFC 4206] Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE).

[RFC 4208] Generalized Multiprotocol Label Switching (GMPLS) User-Network Interface (UNI): Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Support for the Overlay Model.

[RFC 4216] MPLS Inter-Autonomous System (AS) Traffic Engineering (TE) Requirements.

[RFC 4221] Multiprotocol Label Switching (MPLS) Management Overview.

[RFC 4247] Requirements for Header Compression over MPLS.

[RFC 4257] Framework for Generalized Multi-Protocol Label Switching (GMPLS)-based Control of Synchronous Digital Hierarchy/Synchronous Optical Networking (SDH/SONET) Networks.

[RFC 4258] Requirements for Generalized Multi-Protocol Label Switching (GMPLS) Routing for the Automatically Switched Optical Network (ASON).

[RFC 4328] Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for G.709 Optical Transport Networks Control.

[RFC 4364] BGP/MPLS IP Virtual Private Networks (VPNs).

[RFC 4365] Applicability Statement for BGP/MPLS IP Virtual Private Networks (VPNs).

[RFC 4368] Multiprotocol Label Switching (MPLS) Label-Controlled Asynchronous Transfer Mode (ATM) and Frame-Relay Management Interface Definition.

[RFC 4377] Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks.

[RFC 4378] A Framework for Multi-Protocol Label Switching (MPLS) Operations and Management (OAM).

[RFC 4379] Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures.

[RFC 4385] Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN.

[RFC 4397] A Lexicography for the Interpretation of Generalized Multiprotocol Label Switching (GMPLS) Terminology within the Context of the ITU-T's Automatically Switched Optical Network (ASON) Architecture.

[RFC 4426] Generalized Multi-Protocol Label Switching (GMPLS) Recovery Functional Specification.

[RFC 4427] Recovery (Protection and Restoration) Terminology for Generalized Multi-Protocol Label Switching (GMPLS).

[RFC 4428] Analysis of Generalized Multi-Protocol Label Switching (GMPLS)-based Recovery Mechanisms (including Protection and Restoration).

[RFC 4446] IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3).

[RFC 4448] Encapsulation Methods for Transport of Ethernet over MPLS Networks.

[RFC 4461] Signaling Requirements for Point-to-Multipoint Traffic-Engineered MPLS Label Switched Paths (LSPs).

[RFC 5317] Joint Working Team (JWT) Report on MPLS Architectural Considerations for a Transport Profile.

[RFC 5331] MPLS Upstream Label Assignment and Context-Specific Label Space.

[RFC 5332] MPLS Multicast Encapsulations.

[RFC 5339] Evaluation of Existing GMPLS Protocols against Multi-Layer and Multi-Region Networks (MLN/MRN).

[RFC 5439] An Analysis of Scaling Issues in MPLS-TE Core Networks.

[RFC 5623] Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic Engineering.

[RFC 6601] Generic Connection Admission Control (GCAC) Algorithm Specification for IP/MPLS Networks.


Obsolete RFCs:


[RFC 4420] Encoding of Attributes for Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Establishment Using Resource ReserVation Protocol-Traffic Engineering (RSVP-TE).

Description Glossary RFCs Publications Obsolete RFCs