PCEP Extensions for traffic steering support in Service Function Chaining
draft-wu-pce-traffic-steering-sfc-04

Abstract

This document provides an overview of the usage of Path Computation Element (PCE) with Service Function Chaining (SFC); which is described as the definition and instantiation of an ordered set of such service functions (such as firewalls, load balancers), and the subsequent "steering" of traffic flows through those service functions.

Further this document specifies extensions to the Path Computation Element Protocol (PCEP) that allow a stateful PCE to compute and instantiate Service Function Paths (SFP).

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on December 28, 2014.

Copyright Notice

Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

• 1. Introduction
• 2. Conventions used in this document
• 3. Service Function Paths and PCE
• 4. Overview of PCEP Operation in SFC enabled Networks
• 4.1. SFP Instantiation
• 4.2. SFP Deletion
• 4.3. SFP Delegation and Cleanup
• 4.4. SFP State Synchronization
• 4.5. SFP Update and Report
• 5. Object Formats
• 5.1. The OPEN Object
• 5.2. The LSP Object
• 5.2.1. SFP Identifiers TLV
• 6. Backward Compatibility
• 7. Relationship to SR
• 8. Security Considerations
• 9. IANA Considerations
• 10. References
• 10.1. Normative References
• 10.2. Informative References

1. Introduction

Service chaining enables creation of composite services that consist of an ordered set of Service Functions (SF) that must be applied to packets and/or frames selected as a result of classification as described in [I-D.boucadair-sfc-framework][I-D.quinn-sfc-arch] and referred to as Service Function Chain (SFC). Service Function Path (SFP) is the instantiation of a SFC in the network. Packets follow a Service Function Path from a classifier through the requisite Service Functions (SF).

[RFC5440] describes the Path Computation Element Protocol (PCEP) as the communication between a Path Computation Client (PCC) and a Path Control Element (PCE), or between PCE and PCE, enabling computation of Multiprotocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP).

[I-D.ietf-pce-stateful-pce] specifies extensions to PCEP to enable stateful control of MPLS TE LSPs. [I-D.ietf-pce-pce-initiated-lsp] provides the fundamental extensions needed for stateful PCE-initiated LSP instantiation.

This document specifies extensions to the PCEP that allow a stateful PCE to compute and instantiate Service Function Paths (SFP).

2. Conventions used in this document

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 RFC2119 [RFC2119].

The following terminologies are used in this document:

PCC:

Path Computation Client.

PCE:

Path Computation Element.

PCEP:

Path Computation Element Protocol.

PDP:

Policy Decision Point.

SF:

Service Function.

SFC:

Service Function Chain.

SFP:

Service Function Path.

UNI:

User-Network Interface.

3. Service Function Paths and PCE

Services are constructed as a sequence of SFs that represent an SFC, where SF can be a virtual instance or be embedded in a physical network element, and one or more SFs may be deployed within the same physical network element. SFC creates an abstracted view of a service and specifies the set of required SFs as well as the order in which they must be executed.

When an SFC is instantiated into the network it is necessary to select the specific instances of SFs that will be used, and to create the service topology for that SFC using SF's network locator. Thus, instantiation of the SFC results in the creation of a Service Function Path (SFP) and is used for forwarding packets through the SFC. In other words, an SFP is the instantiation of the defined SFC as described in details in [I-D.boucadair-sfc-framework][I-D.quinn-sfc-arch].

The selection of SFP can be based on a range of policy attributes, ranging from simple to more elaborate criteria and stateful PCE with extensions to PCEP are one such way to achieve this.

Stateful pce [I-D.ietf-pce-stateful-pce] specifies a set of extensions to PCEP to enable stateful control of TE LSPs. [I-D.ietf-pce-pce-initiated-lsp] provides the fundamental motivations and extensions needed for stateful PCE-initiated LSP instantiation. This document specifies extensions that allow a stateful PCE to compute and instantiate Service Function Paths (SFP) via PCEP.

           +---------------------------------+
           |+------+ +------+            PDP |
           ||      | |      |                |
           ||      | |      |                |
           ||PCE   | |Policy|                |
           |*------+ +------+                |
           *---------------------------------+
          /
         /
        / SFP
       /  Instan-
      /   tiation
     /             SF Node1            SF Node2
    /              +-------+           +-------+
   V               |       |           |       |
+-----+  Signaling |+-----+| Signaling |+-----+| Signaling  +-----+
|SF-In|----------->||SF-1 || --------->||SF-2 ||----------->|SF-E |
|gress|            ||     ||           ||     ||            |gress|
+-----+            |+-----+|           |+-----+|            +-----+
                   +-------+           +-------+
                      

 
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|            Type=TBD           |            length=4           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                   
|            Reserved           |             Flags             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     
                   

 
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                PLSP-ID                | Flags |F|C|  O|A|R|S|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//                        TLVs                                 //
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+