MPLS Label Forwarding with No Swapping
draft-fang-mpls-label-forwarding-no-swap-00

INTERNET-DRAFT                                               Luyuan Fang
Intended Status: Standards Track                               Microsoft
Expires: January 7, 2016                                   Fabio Chiussi
                                                           Cisco Systems
                                                             Barak Gafni
                                                                Mellanox

                                                            July 6, 2015

                 MPLS Label Forwarding with No Swapping
              draft-fang-mpls-label-forwarding-no-swap-00

Abstract

   This document defines MPLS label forwarding operation with no label
   swapping as a new MPLS label operation extension to the existing
   basic forwarding operation of label push, pop, and swap. 

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
 

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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1. Background  . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3. Label Forwarding  . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     6.1  Normative References  . . . . . . . . . . . . . . . . . . .  6
     6.2  Informative References  . . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  7

 

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1. Introduction

   MPLS forwarding operation as defined in [RFC3031] has three basic
   actions for the labels at the network nodes: push, swap, and pop.
   This document describes an additional operation action: label 
   forwarding, referred to as NO SWAP. Currently, using the same label
   as both incoming and outgoing label is typically achieved by
   "swapping" the incoming label with an identical outgoing label. In
   order to improve processing efficiency and memory usage reduction, a
   simple label forwarding operation with no swap is desirable.

1.1. Background

   When MPLS Architecture [RFC3031] was defined, the three types of
   label operation were sufficient. Label swap operation is performed at
   a Label Switched Router (LSR) which is not an MPLS edge node, while
   label push and pop can be performed at an MPLS edge node for label
   imposition and deposition. Penultimate hop popping can also be
   performed at the penultimate hop for improved efficiency when
   appropriate. Since the labels are assigned independently in
   distributed fashion in a non-traffic engineered basic MPLS networks,
   it is not possible nor necessary to coordinate the label assignment.
   Therefore, the label swapping function is sufficient and effective
   for LSR. 

   With the increased interests and large scale development of Software-
   Defined Networking (SDN), central controller assigned MPLS label
   become one of the option for MPLS based forwarding. A coordinated
   label assignment can be performed by central controller. Use a single
   label to traverse multiple hops along the Label Switched Path (LSP)
   become desirable, therefore the needs to extend the label operation
   with one more action type - forwarding (without swapping).

   The performance and memory efficiency can be increased by performing
   simple forwarding function than swapping the labels with the
   identical identifier. This is an optimization requirement, it does
   not change the fundamentals of MPLS architecture and label encoding
   as defined by [RFC3031] [RFC3032].

1.2. Use Cases

   Hierarchical SDN (HSDN), [I-D.fang-mpls-hsdn-for-hsdc], [HSDNSOSR15]
   is an architectural solution that achieves hyper scale for Cloud
   networks using very small forwarding tables in the network nodes.
   HSDN introduces a new paradigm for the forwarding and control planes
   - all viable paths in the network are pre-established in the
   forwarding tables and the labels identify entire paths rather than
 

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   simply destinations. These properties of HSDN dramatically simplify
   establishing tunnels, and thus enable optimal handling of both ECMP
   and any-to-any end-to-end traffic engineering, which in turn yields
   extremely high network utilization with small buffers in the
   switches. The pre-established tunnels make HSDN the ideal underlay
   infrastructure to enable seamless and lossless VM and VNF overlay
   mobility, and achieve excellent elasticity. HSDN brings important
   simplifications in the control plane and in the architecture of the
   SDN controller.  

   The HSDN forwarding architecture in the underlay network is based on
   four main concepts: 1. Dividing the DC and DCI in a hierarchically-
   partitioned structure; 2. Assigning groups of Underlay Border Nodes
   in charge of forwarding within each partition; 3. Constructing HSDN
   MPLS label stacks to identify the end points according to the HSDN
   structure; and 4. Forwarding using the HSDN MPLS labels.

   Label in HSDN is designed to identify the path and destination, the
   intermediate nodes (non partition border nodes) simply forms the
   label forwarding with the same incoming and outgoing label. Swapping
   the label with the same ID can work, but simple label forwarding
   without swapping performed by hardware can be more efficient as
   optimization.

   In addition to HSDN, there are other source routed label forwarding
   solutions may benefit from the label forwarding operation as well.

2. Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   o  Incoming Label Map (ILM): It maps each incoming label to a set of
      NHLFEs. It is used when forwarding packets that arrive as labeled
      packets.

   o  Label forward: The extended label forwarding operation without
      label swap, consisting of looking up an incoming label to
      determine the outgoing port, and other data handling information.

   o  Label forwarding: A simple forwarding paradigm allowing
      streamlined forwarding of data by using labels to identify classes
      of data packets which are treated indistinguishably when
      forwarding without label swapping.

 

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   o  Label swap: The basic existing forwarding operation consisting of
      looking up an incoming label to determine the outgoing label
      encapsulation, port, and other data handling information.

   o  Label swapping: A forwarding paradigm allowing streamlined
      forwarding of data by using labels to identify classes of data
      packets which are treated indistinguishably when forwarding.

   o  Label Switched Path (LSP): The path through one or more LSRs at
      one level of the hierarchy followed by a packets in a particular
      forwarding equivalence class (FEC).

   o  Label Switching Router (LSR): An MPLS node which is capable of
      forwarding native L3 packets.

   o  MPLS edge node: 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.

   o  NHLFE: Next Hop Label Forwarding Entry

   o  Software-Defined Networking (SDN): an architecture that decouples
      the network control and forwarding functions to enable the network
      control to be directly programmable and the underlying
      infrastructure to be abstracted for applications and network
      services.

3. Label Forwarding 

      Label forwarding is the use of the following procedures to forward
      a packet.

      Same as in [RFC3031], in order to forward a labeled packet, a LSR
      examines the label at the top of the label stack.  It uses the ILM
      to map this label to an NHLFE.  Using the information in the
      NHLFE, it determines where to forward the packet, and performs an
      operation on the packet's label stack.  

      Unlike in label swapping, label forwarding does not remove the
      incoming label and encodes the new label stack into the packet as
      in label swapping, it forwards the packet with the same label
      stack as the incoming stack, to the outgoing interface. Other
      processing may be involved in selecting the outgoing interface,
      for example, load balancing through IP deader hashing or use of
      Entropy label [RFC6790].
 

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4.  Security Considerations

      The MPLS label forwarding operation specified herein does not
      raise any security issues that are not already present in either
      the MPLS architecture [RFC3031] or in MPLS label encoding
      [RFC3032].

      In addition, general MPLS and GMPLS considerations and MPLS
      security defense techniques are documented in [RFC5920].

5.  IANA Considerations

      None.

6.  References

6.1  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, January 2001.

   [RFC6790]  Kompella, K., et.al, "The Use of Entropy Labels in MPLS
              Forwarding", November 2012.

6.2  Informative References

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [I-D.fang-mpls-hsdn-for-hsdc]  L. Fang, et. al., "MPLS-Based
              Hierarchical SDN for Hyper-Scale DC/Cloud", draft-fang-
              mpls-hsdn-for-hsdc-03 (work in progress), July 2015.

   [HSDNSOSR15] L. Fang et al., "Hierarchical SDN for the Hyper-Scale,
              Hyper-Elastic Data Center and Cloud", SOSR '15 Proceedings
              of the 1st ACM SIGCOMM Symposium on Software Defined
              Networking Research. Article No. 7. June 2015. ISBN: 978-
              1-4503-3451-8. URL:
              http://dl.acm.org/citation.cfm?id=2775009

 

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Authors' Addresses

   Luyuan Fang
   Microsoft
   5600 148th Ave NE
   Redmond, WA 98052
   Email: lufang@microsoft.com

   Fabio Chiussi
   Cisco Systems
   500 108th Avenue N.E., Suite 500
   Bellevue, WA 98004 
   Email: fchiussi@cisco.com

   Barak Gafni
   Mellanox
   6 Habarzel St.
   Tel Aviv, Israel
   Email: gbarak@mellanox.com

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