draft-bryant-mpls-sfl-framework-04.txt   draft-bryant-mpls-sfl-framework-05.txt 
MPLS Working Group S. Bryant MPLS Working Group S. Bryant
Internet-Draft M. Chen Internet-Draft M. Chen
Intended status: Informational Z. Li Intended status: Informational Z. Li
Expires: October 27, 2017 Huawei Expires: December 28, 2017 Huawei
G. Swallow G. Swallow
S. Sivabalan S. Sivabalan
Cisco Systems Cisco Systems
G. Mirsky G. Mirsky
Ericsson Ericsson
April 25, 2017 June 26, 2017
Synonymous Flow Label Framework Synonymous Flow Label Framework
draft-bryant-mpls-sfl-framework-04 draft-bryant-mpls-sfl-framework-05
Abstract Abstract
draft-ietf-mpls-flow-ident describes the requirement for introducing draft-ietf-mpls-flow-ident describes the requirement for introducing
flow identities within the MPLS architecture. This document flow identities within the MPLS architecture. This document
describes a method of accomplishing this by using a technique called describes a method of accomplishing this by using a technique called
Synonymous Flow Labels in which labels which mimic the behaviour of Synonymous Flow Labels in which labels which mimic the behaviour of
other labels provide the identification service. These identifiers other labels provide the identification service. These identifiers
can be used to trigger per-flow operations on the on the packet at can be used to trigger per-flow operations on the on the packet at
the receiving label switching router. the receiving label switching router.
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This Internet-Draft will expire on October 27, 2017. This Internet-Draft will expire on December 28, 2017.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Synonymous Flow Labels . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. User Service Traffic in the Data Plane . . . . . . . . . . . 3 3. Synonymous Flow Labels . . . . . . . . . . . . . . . . . . . 3
3.1. Applications Label Present . . . . . . . . . . . . . . . 4 4. User Service Traffic in the Data Plane . . . . . . . . . . . 4
3.1.1. Setting TTL and the Traffic Class Bits . . . . . . . 4 4.1. Applications Label Present . . . . . . . . . . . . . . . 4
3.2. Single Label Stack . . . . . . . . . . . . . . . . . . . 4 4.1.1. Setting TTL and the Traffic Class Bits . . . . . . . 5
3.2.1. Setting TTL and the Traffic Class Bits . . . . . . . 6 4.2. Single Label Stack . . . . . . . . . . . . . . . . . . . 5
3.3. Aggregation of SFL Actions . . . . . . . . . . . . . . . 6 4.2.1. Setting TTL and the Traffic Class Bits . . . . . . . 6
4. Equal Cost Multipath Considerations . . . . . . . . . . . . . 7 4.3. Aggregation of SFL Actions . . . . . . . . . . . . . . . 6
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 7 5. Equal Cost Multipath Considerations . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
[I-D.ietf-mpls-flow-ident] describes the requirement for introducing [I-D.ietf-mpls-flow-ident] describes the requirement for introducing
flow identities within the MPLS architecture. flow identities within the MPLS architecture.
This document describes a method of accomplishing this by using a This document describes a method of accomplishing this by using a
technique called Synonymous Flow Labels (SFL) (see (Section 2)) in technique called Synonymous Flow Labels (SFL) (see (Section 2)) in
which labels which mimic the behaviour of other labels provide the which labels which mimic the behaviour of other labels provide the
identification service. These identifiers can be used to trigger identification service. These identifiers can be used to trigger
per-flow operations on the packet at the receiving label switching per-flow operations on the packet at the receiving label switching
router. router.
2. Synonymous Flow Labels 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Synonymous Flow Labels
An SFL is defined to be a label that causes exactly the same An SFL is defined to be a label that causes exactly the same
behaviour at the egress Label Switching Router (LSR) as the label it behaviour at the egress Label Switching Router (LSR) as the label it
replaces, but in addition also causes an agreed action to take place replaces, but in addition also causes an agreed action to take place
on the packet. There are many possible additional actions such as on the packet. There are many possible additional actions such as
the measurement of the number of received packets in a flow, the measurement of the number of received packets in a flow,
triggering IPFIX inspection, triggering other types of Deep Packet triggering IPFIX inspection, triggering other types of Deep Packet
Inspection, or identification of the packet source. In, for example, Inspection, or identification of the packet source. In, for example,
a Performance Monitoring (PM) application, the agreed action could be a Performance Monitoring (PM) application, the agreed action could be
the recording of the receipt of the packet by incrementing a packet the recording of the receipt of the packet by incrementing a packet
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acceptable for scaling reasons. We therefore have no choice but to acceptable for scaling reasons. We therefore have no choice but to
introduce an additional label. Where penultimate hop popping (PHP) introduce an additional label. Where penultimate hop popping (PHP)
is in use, the semantics of this additional label can be similar to is in use, the semantics of this additional label can be similar to
the LSP label. Where PHP is not in use, the semantics are similar to the LSP label. Where PHP is not in use, the semantics are similar to
an MPLS explicit NULL. In both of these cases the label has the an MPLS explicit NULL. In both of these cases the label has the
additional semantics of the SFL. additional semantics of the SFL.
Note that to achieve the goals set out in Section 1 SFLs need to be Note that to achieve the goals set out in Section 1 SFLs need to be
allocated from the platform label table. allocated from the platform label table.
3. User Service Traffic in the Data Plane 4. User Service Traffic in the Data Plane
As noted in Section 2 it is necessary to consider two cases: As noted in Section 3 it is necessary to consider two cases:
1. Applications label present 1. Applications label present
2. Single label stack 2. Single label stack
3.1. Applications Label Present 4.1. Applications Label Present
Figure 1 shows the case in which both an LSP label and an application Figure 1 shows the case in which both an LSP label and an application
label are present in the MPLS label stack. Traffic with no SFL label are present in the MPLS label stack. Traffic with no SFL
function present runs over the "normal" stack, and SFL enabled flows function present runs over the "normal" stack, and SFL enabled flows
run over the SFL stack with the SFL used to indicate the packet run over the SFL stack with the SFL used to indicate the packet
batch. batch.
+-----------------+ +-----------------+ +-----------------+ +-----------------+
| | | | | | | |
| LSP | | LSP | <May be PHPed | LSP | | LSP | <May be PHPed
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+-----------------+ +-----------------+ +-----------------+ +-----------------+
"Normal" Label Stack Label Stack with SFL "Normal" Label Stack Label Stack with SFL
Figure 1: Use of Synonymous Labels In A Two Label MPLS Label Stack Figure 1: Use of Synonymous Labels In A Two Label MPLS Label Stack
At the egress LSR the LSP label is popped (if present). Then the SFL At the egress LSR the LSP label is popped (if present). Then the SFL
is processed in exactly the same way as the corresponding application is processed in exactly the same way as the corresponding application
label would have been processed. label would have been processed.
3.1.1. Setting TTL and the Traffic Class Bits 4.1.1. Setting TTL and the Traffic Class Bits
The TTL and the Traffic Class bits [RFC5462] in the SFL LSE would The TTL and the Traffic Class bits [RFC5462] in the SFL LSE would
normally be set to the same value as would have been set in the label normally be set to the same value as would have been set in the label
that the SFL is synonymous with. However it is recognised that there that the SFL is synonymous with. However it is recognised that there
may be an applications need to set the SFL to some other value. An may be an applications need to set the SFL to some other value. An
example would be where it was desired to cause the SFL to trigger an example would be where it was desired to cause the SFL to trigger an
action in the TTL expiry exception path as part of the label action. action in the TTL expiry exception path as part of the label action.
3.2. Single Label Stack 4.2. Single Label Stack
Figure 2 shows the case in which only an LSP label is present in the Figure 2 shows the case in which only an LSP label is present in the
MPLS label stack. Traffic with no SFL function present runs over the MPLS label stack. Traffic with no SFL function present runs over the
"normal" stack and SFL enabled flows run over the SFL stack with the "normal" stack and SFL enabled flows run over the SFL stack with the
SFL used to indicate the packet batch. However in this case it is SFL used to indicate the packet batch. However in this case it is
necessary for the ingress LSR to first push the SFL and then to push necessary for the ingress LSR to first push the SFL and then to push
the LSP label. the LSP label.
+-----------------+ +-----------------+
| | | |
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If the LSP label is not present due to PHP action in the upstream If the LSP label is not present due to PHP action in the upstream
LSR, two almost equivalent processing actions can take place. Either LSR, two almost equivalent processing actions can take place. Either
the SFL can be treated as an LSP label that was not PHPed and the the SFL can be treated as an LSP label that was not PHPed and the
additional associated SFL action is taken when the label is additional associated SFL action is taken when the label is
processed. Alternatively, it can be treated as an explicit NULL with processed. Alternatively, it can be treated as an explicit NULL with
associated SFL actions. From the perspective of the measurement associated SFL actions. From the perspective of the measurement
system described in this document the behaviour of two approaches are system described in this document the behaviour of two approaches are
indistinguishable and thus either may be implemented. indistinguishable and thus either may be implemented.
3.2.1. Setting TTL and the Traffic Class Bits 4.2.1. Setting TTL and the Traffic Class Bits
The TTL and the Traffic Class considerations described in The TTL and the Traffic Class considerations described in
Section 3.1.1 apply. Section 4.1.1 apply.
3.3. Aggregation of SFL Actions 4.3. Aggregation of SFL Actions
There are cases where it is desirable to aggregate an SFL action There are cases where it is desirable to aggregate an SFL action
against a number of labels. For example where it is desirable to against a number of labels. For example where it is desirable to
have one counter record the number of packets received over a group have one counter record the number of packets received over a group
of application labels, or where the number of labels used by a single of application labels, or where the number of labels used by a single
application is large, and consequently the increase in the number of application is large, and consequently the increase in the number of
allocated labels needed to support the SFL actions consequently allocated labels needed to support the SFL actions consequently
becomes too large to be viable. In these circumstances it would be becomes too large to be viable. In these circumstances it would be
necessary to introduce an additional label in the stack to act as an necessary to introduce an additional label in the stack to act as an
aggregate instruction. This is not strictly a synonymous action in aggregate instruction. This is not strictly a synonymous action in
that the SFL is not replacing a existing label, but is somewhat that the SFL is not replacing a existing label, but is somewhat
similar to the single label case shown in Section 3.2, and the same similar to the single label case shown in Section 4.2, and the same
signalling, management and configuration tools would be applicable. signalling, management and configuration tools would be applicable.
+-----------------+ +-----------------+
| | | |
| LSP | < May be PHPed | LSP | < May be PHPed
| Label | | Label |
+-----------------+ +-----------------+ +-----------------+ +-----------------+
| | | | | | | |
| LSP | | Aggregate | | LSP | | Aggregate |
| Label | | SFL | | Label | | SFL |
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| | | | | | | |
+-----------------+ +-----------------+ +-----------------+ +-----------------+
"Normal" Label Stack Label Stack with SFL "Normal" Label Stack Label Stack with SFL
Figure 3: Aggregate SFL Actions Figure 3: Aggregate SFL Actions
The Aggregate SFL is shown in the label stack depicted in Figure 3 as The Aggregate SFL is shown in the label stack depicted in Figure 3 as
preceding the application label, however the choice of position preceding the application label, however the choice of position
before, or after, the application label will be application specific. before, or after, the application label will be application specific.
In the case described in Section 3.1, by definition the SFL has the In the case described in Section 4.1, by definition the SFL has the
full application context. In this case the positioning will depend full application context. In this case the positioning will depend
on whether the SFL action needs the full context of the application on whether the SFL action needs the full context of the application
to perform its action and whether the complexity of the application to perform its action and whether the complexity of the application
will be increased by finding an SFL following the application label. will be increased by finding an SFL following the application label.
4. Equal Cost Multipath Considerations 5. Equal Cost Multipath Considerations
The introduction to an SFL to an existing may cause that flow to take The introduction to an SFL to an existing flow may cause that flow to
a different path through the network under conditions of Equal Cost take a different path through the network under conditions of Equal
Multipath (ECMP). This is turn may invalidate the certain uses of Cost Multipath (ECMP). This is turn may invalidate the certain uses
the SFL such as performance measurement applications. Where this is of the SFL such as performance measurement applications. Where this
a problem there are two solutions worthy of consideration: is a problem there are two solutions worthy of consideration:
1. The operator can elect to always run with the SFL in place in the 1. The operator can elect to always run with the SFL in place in the
MPLS label stack. MPLS label stack.
2. The operator can elect to use [RFC6790] Entropy Labels which, in 2. The operator can elect to use [RFC6790] Entropy Labels in a
a network that fully supports this type of ECMP, results in the network that fully supports this type of ECMP. If this approach
ECMP decision being independent of the value of the other labels is adopted, the intervening MPLS network MUST NOT load balance on
in the label stack. any packet field other than the entropy label. Note that this is
stricter than the text in Section 4.2 of [RFC6790]. In networks
in which the ECMP decision is independent of both the value of
any other label in the label stack, and the MPLS payload, the
path of the flow with the SFL will be congruent with the path
without the SFL.
5. Privacy Considerations 6. Privacy Considerations
Recent IETF concerns on pervasive monitoring are described in Recent IETF concerns on pervasive monitoring are described in
[RFC7258]. The inclusion of originating and/or flow information in a [RFC7258]. The inclusion of originating and/or flow information in a
packet provides more identity information and hence potentially packet provides more identity information and hence potentially
degrades the privacy of the communication. Whilst the inclusion of degrades the privacy of the communication. Whilst the inclusion of
the additional granularity does allow greater insight into the flow the additional granularity does allow greater insight into the flow
characteristics it does not specifically identify which node characteristics it does not specifically identify which node
originated the packet other than by inspection of the network at the originated the packet other than by inspection of the network at the
point of ingress, or inspection of the control protocol packets. point of ingress, or inspection of the control protocol packets.
This privacy threat may be mitigated by encrypting the control This privacy threat may be mitigated by encrypting the control
protocol packets, regularly changing the synonymous labels and by protocol packets, regularly changing the synonymous labels and by
concurrently using a number of such labels. Minimizing the scope of concurrently using a number of such labels. Minimizing the scope of
the identity indication can be useful in minimizing the observability the identity indication can be useful in minimizing the observability
of the flow characteristics. of the flow characteristics.
6. Security Considerations 7. Security Considerations
The issue noted in Section 5 is a security consideration. There are The issue noted in Section 6 is a security consideration. There are
no other new security issues associated with the MPLS dataplane. Any no other new security issues associated with the MPLS dataplane. Any
control protocol used to request SFLs will need to ensure the control protocol used to request SFLs will need to ensure the
legitimacy of the request. legitimacy of the request.
7. IANA Considerations 8. IANA Considerations
This draft makes no IANA requests. This draft makes no IANA requests.
8. References 9. References
8.1. Normative 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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <http://www.rfc-editor.org/info/rfc5462>. 2009, <http://www.rfc-editor.org/info/rfc5462>.
8.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[I-D.ietf-mpls-flow-ident] [I-D.ietf-mpls-flow-ident]
Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
Mirsky, "MPLS Flow Identification Considerations", draft- Mirsky, "MPLS Flow Identification Considerations", draft-
ietf-mpls-flow-ident-04 (work in progress), February 2017. ietf-mpls-flow-ident-04 (work in progress), February 2017.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011, DOI 10.17487/RFC6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>. <http://www.rfc-editor.org/info/rfc6374>.
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