IDR Working Group Q. Liang
Internet-Draft S. Hares
Intended status: Standards Track J. You
Expires: September 22, 2016 Huawei
R. Raszuk
Bloomberg LP
D. Ma
March 21, 2016

BGP Flow Specification MPLS action


This document specifies a BGP Flow specification policy action to push/pop/swap MPLS labels.

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Table of Contents

1. Introduction

This section provides the background for proposing a new action for BGP Flow specification [RFC5575] that push/pops MPLS labels or swaps MPLS labels. For those familiar with BGP Flow specification ([RFC5575], [RFC7674] [I-D.ietf-idr-flow-spec-v6], [I-D.ietf-idr-flowspec-l2vpn], and MPLS ([RFC3107]) can skip this background section.

1.1. Background

[RFC5575] defines the flow specification (FlowSpec) that is an n-tuple consisting of several matching criteria that can be applied to IP traffic. The matching criteria can include elements such as source and destination address prefixes, IP protocol, and transport protocol port numbers. A given IP packet is said to match the defined flow if it matches all the specified criteria. [RFC5575] also defines a set of filtering actions, such as rate limit, redirect, marking, associated with each flow specification. A new Border Gateway Protocol ([RFC4271]) Network Layer Reachability Information (BGP NLRI) (AFI/SAFI: 1/133 for IPv4, AFI/SAFI: 1/134 for VPNv4) encoding format is used to distribute traffic flow specifications.

[RFC3107] specifies the way in which the label mapping information for a particular route is piggybacked in the same Border Gateway Protocol Update message that is used to distribute the route itself. Label mapping information is carried as part of the Network Layer Reachability Information (NLRI) in the Multiprotocol Extensions attributes. The Network Layer Reachability Information is encoded as one or more triples of the form <length, label, prefix>. The NLRI contains a label is indicated by using Subsequent Address Family Identifier (SAFI) value 4.

[RFC4364] describes a method in which each route within a Virtual Private Network (VPN) is assigned a Multiprotocol Label Switching (MPLS) label. If the Address Family Identifier (AFI) field is set to 1, and the SAFI field is set to 128, the NLRI is an MPLS-labeled VPN- IPv4 address.

1.2. MPLS Flow Specification Deployment

In BGP VPN/MPLS networks when flow specification policy rules exist on multiple forwarding devices in the network bound with labels from one or more LSPs, only the ingress LSR (Label Switching Router) needs to identify a particular traffic flow based on the matching criteria for flow. Once the flow is match by the ingress LSR, the ingress LSR steers the packet to a corresponding LSP (Label Switched Path). Other LSRs of the LSP just need to forward the packet according to the label carried in it.

2. Terminology

Flow Specification (FlowSpec): A flow specification is an n-tuple consisting of several matching criteria that can be applied to IP traffic, including filters and actions. Each FlowSpec consists of a set of filters and a set of actions.

2.1. Requirements Language

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].

3. Overview of Proposal

This document proposes adding a BGP-FS action in an extended community alters the label switch path associated with a matched flow. If the match does not have a label switch path, this action is skipped.

The BGP flow specification (BGP-FS) policy rule could match on the destination prefix and then utilize a BGP-FS action to adjust the label path associated with it (push/pop/swap tags.) Or a BGP-FS policy rule could match on any set of BGP-FS match conditions associated with a BGP-FS action that adjust the label switch path (push/pop/swap).

draft-ietf-yong-flowspec-mpls-match provides a match BGP-FS that may be used with this action to match and direct MPLS packets.

4. Protocol Extensions

A new label-action is defined as BGP extended community value based on Section 7 of [RFC5575].

   | type   | extended community | encoding                 |
   | TBD1   | label-action       | MPLS tag                 |
   Figure 1

  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  (TBD1              | OpCode|Reserve| order         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Label
 |                Label                  | Exp |S|       TTL     | Stack
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Entry
    The use and the meaning of these fields are as follows:

      Type: the same as defined in [RFC4360]

   Figure 2 

Label-action is described below:

   |OpCode| Function                                                   |
   |  0   | Push the MPLS tag                                          |
   |  1   | Pop the outermost MPLS tag in the packet                   |
   |  2   | Swap the MPLS tag with the outermost MPLS tag in the packet|
   | 3~15 | Reserved                                                   |

OpCode: Operation code

Reserved: all zeros
Order: within multiple label actions
A FlowSpec rule MAY be associated with one or more ordering label-action each in an extended community. If multiple label-actions occur, this field gives the order of this action within that group. If two MPLs actions arrive with the same order the last mpls action received for an order will be used.
the same as defined in [RFC3032]
Bottom of Stack (S):
the same as defined in [RFC3032]. It SHOULD be invalid, and set to zero by default. It MAY be modified by the forwarding router locally.
Time to Live (TTL):
the same as defined in [RFC3032]. It MAY be modified by the forwarding router locally.
Experimental Use (Exp):
the same as defined in [RFC3032]. It MAY be modified by the forwarding router according to the local routing policy.

5. Deployment Examples

5.1. Exampel 1 - MPLS Filter + MPLS Action

   Forwarding information for the traffic 
      for source: IP2, Destination: IP1 
   Purpose of BGP-FS filters: send DDoS traffic to IDS/IPS server
	   PE1:   in(<IP2,IP1>) --> out(Label1)
       ASBR1: in(Label1) --> out(Label1)
       ASBR2: in(Label1) --> out(Label2)
       PE2:   in(Label2) --> out(--)	   
            |<------AS1----->|    |<------AS2----->|
            +-----+    +------+    +------+    +-----+
 VPN 1,IP1..| PE1 |====|ASBR-1|----|ASBR-2|====| PE2 |..IDS/IPS  
       IP2  +-----+    +------+    +------+    +-----+
	        |-----label 1---------||-label 2---------|
            |---------BGP VPN Flowspec LSP--------->|

		  Figure 1 - Forwarding Diagram 

     locally configured filters   
          destination ip prefix:IP2/32
          source      ip prefix:IP1/32
          put on LSP with Label 1 

    PE-2 Installs:
	  BGP-FS Filter: 
	     MPLS filter for Label 1 and label 2
      BGP-FS Actions:   
         Traffic-Rate limit
         MPLS POP 
    PE-2 Sends to ASBR-2
       BGP-FS Filter 
         MPLS filter for label 1 and Label 2
       BGP-FS Actions: 	
         Traffic-Rate limit	   
         Label SWAP 1 to 2 
    PE-1 Sends to ASBR 1
       BGP-FS filter
 	     MPLS filter for label 1
	   BGP-FS Actions 
           Traffic-Rate limit	

5.2. Example 2 - IP filter + MPLS action

   Forwarding information for the traffic from IP1 to IP2 in the Routers:
       PE1:   in(<IP2,IP1>) --> out(Label2)
       ASBR1: in(Label2) --> out(Label3)
       ASBR2: in(Label3) --> out(Label4)
       PE2:   in(Label4) --> out(--)

     Labels allocated by Flow policy process 
       Label4 allocated by PE2
       Label3 allocated by ASBR2
       Label2 allocated by ASBR1

            |<------AS1----->|    |<------AS2----->|
            +-----+    +-----+    +-----+    +-----+
 VPN 1,IP1..| PE1 |====|ASBR1|----|ASBR2|====| PE2 |.. 
       IP2  +-----+    +-----+    +-----+    +-----+
            | LDP LSP1 |          | LDP LSP2 |
            | -------> |          | -------> |
            |-------BGP VPN Flowspec LSP---->|
                     (Label2)   (Label3)   (Label4)

		  Figure 1 - Forwarding Diagram 

  BGP-FS rule1 (locally configured) 
          destination ip prefix:IP2/32
          source      ip prefix:IP1/32
          traffic-marking: 1   
          MPLS POP 
       The following Extended Communities are added/deleted 
       [rule-1a] BGP-FS action MPLS POP [used on PE2]  
       [rule-1b] BGP-FS action SWAP 4   [used on ASBR-2]
       [rule-1c] BGP-FS action SWAP 3   [used on ASBR-1]
       [rule-1d] BGP-FS action push 2   [used on PE1] 

	  BGP Filter rules 

   PE-2 Changes BGP-FS rule-1a to rule-1b prior to sending
       Clears Extended Community: BGP-FS action MPLS POP 
       Adds   Extended Community: BGP-FS action MPLS SWAP 4
  ASBR-2 receives BGP-FS rule-1b (NRLI + 2 Extended Community)
         Installs the BGP-FS rule-1b (MPLS SWAP 4, traffic-marking)  
         Changes BGP-FS rule-1b to rule-1c prior to sending to ASBR1 
         Clear Extended Community: BGP-FS action MPLS SWAP 4
         Adds  Extended Community: BGP-FS action MPLS SWAP 3

  ASBR-1 Receives BGP-FS rule-1c (NLRI + 2 Extended Community)
         Installs the BGP-FS rule-1c (MPLS SWAP 3, traffic-marking
         Changes BGP-FS rule-1c to rule-1d prior to sending to PE-2 
         Clear Extended Community: BGP-FS action MPLS SWAP 3
         Adds  Extended Community: BGP-FS action MPLS SWAP 2 

  PE-1   Receives BGP-FS rule-1d (NLRI + 2 Extended Communities)
         Installs BGP-FS rule-1d action [MPLS SWAP 2, traffic-marking]  


6. Security Considerations

The validation of BGP Flow Specification policy in NLRI is considered in [I-D.hares-idr-flowspec-combo] for option 1, and for option 2. Additional security has been proposed in [I-D.ietf-idr-bgp-flowspec-oid]. A BGP5575bis document will consider the revised security.

For Option 1, the MPLS Match can be one of the match filters, and and the final match is an “AND” of all the filters. Match filters are tested in the order specified in [I-D.hares-idr-flowspec-combo] and/or an RFC5575bis document.

[I-D.hares-idr-flowspec-combo] suggests a default order for filters and for the BGP-FS action proposed after [RFC5575], and this document discusses how conflicts between action are handled.

7. IANA Considerations

This section complies with [RFC7153]

    Value Name:    Value  Reference 
	===========    =====  =========
    Lable Action   TBD    [this document]

IANA is requested to a new entry in “Flow Spec action types registry” with the following values:

8. Acknowledgement

The authors would like to thank Shunwan Zhuang, Zhenbin Li, Peng Zhou and Jeff Haas for their comments.

9. References

9.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T. and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006.
[RFC4360] Sangli, S., Tappan, D. and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 2006.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 2006.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J. and D. McPherson, "Dissemination of Flow Specification Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014.
[RFC7674] Haas, J., "Clarification of the Flowspec Redirect Extended Community", RFC 7674, DOI 10.17487/RFC7674, October 2015.

9.2. Informative References

[I-D.filsfils-spring-segment-routing-central-epe] Filsfils, C., Previdi, S., Patel, K., Shaw, S., Ginsburg, D. and D. Afanasiev, "Segment Routing Centralized Egress Peer Engineering", Internet-Draft draft-filsfils-spring-segment-routing-central-epe-05, August 2015.
[I-D.hares-idr-flowspec-combo] Hares, S., "An Information Model for Basic Network Policy and Filter Rules", Internet-Draft draft-hares-idr-flowspec-combo-01, March 2016.
[I-D.ietf-idr-bgp-flowspec-oid] Uttaro, J., Filsfils, C., Smith, D., Alcaide, J. and P. Mohapatra, "Revised Validation Procedure for BGP Flow Specifications", Internet-Draft draft-ietf-idr-bgp-flowspec-oid-02, January 2014.
[I-D.ietf-idr-flow-spec-v6] McPherson, D., Raszuk, R., Pithawala, B., Andy, A. and S. Hares, "Dissemination of Flow Specification Rules for IPv6", Internet-Draft draft-ietf-idr-flow-spec-v6-07, March 2016.
[I-D.ietf-idr-flowspec-l2vpn] Weiguo, H., Litkowski, S. and S. Zhuang, "Dissemination of Flow Specification Rules for L2 VPN", Internet-Draft draft-ietf-idr-flowspec-l2vpn-03, November 2015.
[I-D.yong-idr-flowspec-mpls-match] Yong , L., Hares , S., Liang , Q. and J. You , "BGP Flow Specification Filter for MPLS Label", March 2016.

Authors' Addresses

Qiandeng Liang Huawei 101 Software Avenue, Yuhuatai District Nanjing, 210012 China EMail:
Susan Hares Huawei 7453 Hickory Hill Saline, MI 48176 USA EMail:
Jianjie You Huawei 101 Software Avenue, Yuhuatai District Nanjing, 210012 China EMail:
Robert Raszuk Bloomberg LP 731 Lexington Ave New York City, NY 10022 USA EMail:
Dan Ma Cisco EMail: