Idr Working Group Q. Liang
Internet-Draft J. You
Intended status: Standards Track Huawei
Expires: January 6, 2016 July 5, 2015
Carrying Label Information for BGP FlowSpec
draft-liang-idr-bgp-flowspec-label-00
Abstract
This document specifies a method in which the label mapping
information for a particular FlowSpec rule is piggybacked in the same
Border Gateway Protocol (BGP) Update message that is used to
distribute the FlowSpec rule. Based on the proposed method, the
Label Switching Routers (LSRs) (except the ingress LSR) on the Label
Switched Path (LSP) can use label to indentify the traffic matching a
particular FlowSpec rule; this facilitates monitoring and traffic
statistics for FlowSpec rules. Meanwhile, using label for FlowSpec
rule can improve forwarding performance in BGP VPN/MPLS networks.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 6, 2016.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[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 filtering actions, such as rate limit, redirect,
marking, associated with each flow specification. A new Border
Gateway Protocol 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
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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.
In BGP VPN/MPLS networks, label switching is more efficient than IP
routing. As FlowSpec rules are used for packet processing and
forwarding, label-based forwarding can effectively improve the route
lookup performance in the data plane. When FlowSpec rules on
multiple forwarding devices in the network bound with labels form one
or more LSPs, only the ingress LSR (Label Switching Router) needs to
identify a particular traffic flow based on the matching criteria and
then 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.
Though the FlowSpec rule could use the label(s) bound with the best-
match unicast route for the destination prefix embedded in the
FlowSpec rule or the best-match route to the target IP in the
'redirect to IP' action, this way means that if two or more FlowSpec
rules have the same best-match unicast route for the embedded
destination prefix or the same best-match route to target IP in the
'redirect to IP' action; they would be mapped to the same label.
This would affect monitoring and traffic statistics facilities,
because each FlowSpec rule requires an independent statistic and log
data, which is described in Section 9 [RFC5575]. The LSRs (except
the ingress LSR) on the LSP can use label to indentify the traffic
matching a particular FlowSpec rule; this facilitates monitoring and
traffic statistics for FlowSpec rules.
So this document proposes that the BGP router supports to allocate a
unique label to a FlowSpec rule, the forwarding path is still decided
by the best-match unicast route for the embedded destination prefix
or the best-match route to target IP in the 'redirect to IP' action.
Figure 1 gives an example that FlowSpec rule bound with a label is
disseminated in the network.
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Option-B inter-AS connection
|<------AS1----->| |<------AS2----->|
+-----+ +-----+ +-----+ +-----+
VPN 1,IP1..| PE1 |====|ASBR1|----|ASBR2|====| PE2 |..VPN1,IP2
+-----+ +-----+ +-----+ +-----+
| LDP LSP1 | | LDP LSP2 |
| -------> | | -------> |
|-------BGP VPN Flowspec LSP---->|
(Label1) (Label2) (Label3) (Label4)
Figure 1: Usage of FlowSpec with Label
FlowSpec rule1 (injected in PE2):
Filters:
destination ip prefix:IP2/32
source ip prefix:IP1/32
Actions:
traffic-marking: 1
Labels allocated for FlowSpec1:
Label4 allocated by PE2
Label3 allocated by ASBR2
Label2 allocated by ASBR1
Label1 allocated by PE1
PE2 disseminates the FlowSpec1 bound with Label4 to ASBR2.
ASBR2 disseminates the FlowSpec1 bound with Label3 to ASBR1.
ASBR1 disseminates the FlowSpec1 bound with Label2 to PE1.
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(--)
So ASBR1 can do traffic statistics for FlowSpec rule 1 based on
Label2; ASBR2 can do it based on Label3; and PE2 can do it based on
Label4.
2. Terminology
This section contains definitions of terms used in this document.
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.
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3. Protocol Extensions
In this document, BGP is used to distribute the FlowSpec rule bound
with label(s). Two new SAFIs should be defined, i.e. SAFI: TBD1 for
IP FlowSpec rule bound with label(s), SAFI: TBD2 for VPN FlowSpec
rule bound with label(s). The Network Layer Reachability Information
for this FlowSpec rule is encoded as one or more triples of the form
<length, RD (optional), FlowSpec, label(s) (optional)>, whose fields
are described below:
+---------------------------+
| Length (1 or 2 octets) |
+---------------------------+
| RD (8 octets, optional) |
+---------------------------+
| Flow Filters (variable) |
+---------------------------+
| Separator |
+---------------------------+
| Label(s) |
+---------------------------+
The use and the meaning of these fields are as follows:
Length: The Length field indicates the length in bytes of the flow
filters, the RD, the separator and the label(s).
RD: Route Distinguisher (8 bytes), when SAFI=TBD2.
Separator: This field is the constant bit pattern 0xfe (hex),which
indicates the separation between the flow filters field and
lable(s) field. This value should not be used by flow filters.
Label(s): This field carries zero or more labels (that corresponds
to the stack of labels [RFC3032]). Each label is encoded as 3
octets, where the high-order 20 bits contain the label value, and
the low order bit contains "Bottom of Stack" [RFC3032].
Flow Filters: This field consists of several optional
subcomponents defined in section 4 [RFC5575]. The combination of
RD and Flow Filters is equal to the flow-spec NLRI defined in
[RFC5575].
For the purpose of BGP route key processing, only the Route
Distinguisher, Flow Filters fields are considered to be part of the
prefix in the NLRI.
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4. IANA Considerations
For the purpose of this work, IANA should allocate values for two
SAFIs:
SAFI TBD1 for IP FlowSpec rule bound with label(s).
SAFI TBD2 for VPN FlowSpec rule bound with label(s).
5. Security considerations
This extension to BGP does not change the underlying security issues
inherent in the existing BGP.
6. Acknowledgement
The authors would like to thank Shunwan Zhuang, Zhenbin Li and Peng
Zhou for their comments.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, August 2009.
Authors' Addresses
Qiandeng Liang
Huawei
101 Software Avenue, Yuhuatai District
Nanjing, 210012
China
Email: liangqiandeng@huawei.com
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Jianjie You
Huawei
101 Software Avenue, Yuhuatai District
Nanjing, 210012
China
Email: youjianjie@huawei.com
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