Internet DRAFT - draft-bailmir-ippm-twamp-dscp-ctrl-mon
draft-bailmir-ippm-twamp-dscp-ctrl-mon
Network Working Group G. Mirsky
Internet-Draft ZTE Corp.
Updates: 5357, 7750 (if approved) S. Baillargeon
Intended status: Standards Track Ericsson
Expires: August 25, 2017 February 21, 2017
Control and Monitoring Differentiated Service Code Point in Two-Way
Active Measurement Protocol (TWAMP)
draft-bailmir-ippm-twamp-dscp-ctrl-mon-02
Abstract
This document describes an optional extension for Two-Way Active
Measurement Protocol (TWAMP) allowing control and monitoring of the
Differentiated Service Code Point (DSCP) field in forward and reverse
directions within single test session with the TWAMP-Test protocol.
This document, if accepted, will be an update to the TWAMP core
protocol specified in RFC 5357 and DSCP Monitoring mode defined in
RFC 7750 .
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 25, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. TWAMP Extensions . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Setting Up Connection to Test DSCP and ECN . . . . . . . 4
2.2. TWAMP-Test Extension . . . . . . . . . . . . . . . . . . 4
2.2.1. Session-Sender Packet Format for DSCP and ECN Testing 4
2.2.2. Combining DSCP and ECN Testing and Monitoring
extensions . . . . . . . . . . . . . . . . . . . . . 6
2.2.3. DSCP and ECN Testing with RFC 6038 extensions . . . . 6
2.2.4. Consideration for TWAMP Light mode . . . . . . . . . 7
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The One-Way Active Measurement Protocol (OWAMP) [RFC4656] defines the
Type-P Descriptor field and negotiation of its value in OWAMP-Control
protocol. The Two-Way Active Measurement Protocol (TWAMP) [RFC5357]
states that only a Differentiated Services Code Point (DSCP)
[RFC2474], [RFC3168], [RFC3260] value can be defined by Type-P
Descriptor and the negotiated value must be used by both Session-
Sender and Session-Reflector. The TWAMP specification also states
that the same DSCP value (found in the Session-Sender packet) MUST be
used in the test packet reflected by the Session-Reflector. The
[RFC7750] introduced optional DSCP Monitoring mode that can be
negotiated using TWAMP Control protocol and supported by TWAMP-Test
protocol or by TWAMP Light mode. Still the TWAMP-Test protocol does
not support discovery of how Differentiated Services policies
configured along the IP path process various DSCP values in single
test session. Hence method defined in [RFC7750] can be characterized
as per-session DSCP Monitoring. To provide higher efficiency and
flexibility to monitoring how Differentiated Services policies being
applied this document proposes ability to control DSCP value to be
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used by Session-Reflector for each TWAMP-Test packet. Such method
can be characterized as per-packet DSCP monitoring with TWAMP.
This document describes an OPTIONAL feature for TWAMP. It is called
the DSCP and ECN Testing. It allows the Session-Sender to use set of
DSCP values through single test session and to instruct the Session-
Reflector on what DSCP value it must use for the reflected test
packet. Furthermore this feature tracks the Explicit Congestion
Notification (ECN) [RFC2474], [RFC3168], [RFC3260] value received at
the Session-Reflector. This is helpful to determine if ECN is
actually operating or if an ECN-capable node has detected congestion
in the forward direction.
1.1. Conventions used in this document
1.1.1. Terminology
DSCP: Differentiated Services Code Point
ECN: Explicit Congestion Notification
IPPM: IP Performance Metrics
TWAMP: Two-Way Active Measurement Protocol
OWAMP: One-Way Active Measurement Protocol
1.1.2. 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
[RFC2119].
2. TWAMP Extensions
TWAMP connection establishment follows the procedure defined in
Section 3.1 of [RFC4656] and Section 3.1 of [RFC5357] where the Modes
field is used to identify and select specific communication
capabilities. At the same time the Modes field been recognized and
used as an extension mechanism [RFC6038]. The new feature requires a
new flag to identify the ability of a Session-Reflector to support
the new Session-Sender packet format in the TWAMP-Test protocol and
to use received DSCP and ECN values in the reflected to a Session-
Sender test packet, See the Section 3 for details on the assigned bit
position.
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2.1. Setting Up Connection to Test DSCP and ECN
The Server sets the DSCP and ECN Testing flag in the Modes field of
the Server Greeting message to indicate its capabilities and
willingness to monitor them. If the Control-Client agrees to test
DSCP and ECN on some or all test sessions invoked with this control
connection, it MUST set the DSCP and ECN Testing flag in the Modes
field in the Setup Response message.
2.2. TWAMP-Test Extension
Testing of DSCP and ECN requires support by the Session-Sender and
changes the test packet format in all the original (unauthenticated,
authenticated and encrypted) modes. Testing of DSCP and ECN does not
alter the Session-Reflector test packet format but certain
considerations must be taken when and if this mode is accepted in
combination with Symmetrical Size mode [RFC6038] and/or with DSCP and
ECN Monitoring mode [RFC7750].
2.2.1. Session-Sender Packet Format for DSCP and ECN Testing
When the Session-Sender supports DSCP and ECN Testing it constructs
the Reflector DSCP and ECN (R-DSCP-ECN) field, presented in Figure 1,
for each test packet it sends to Session-Reflector according to the
following procedure:
o value of the Reflector DSCP (R-DSCP) field MUST be set to the
value that the Session-Reflector MUST use for the reflected test
packet;
o value of the Reflector ECN (R-ECN) field MUST be set to the value
that the Session-Reflector MAY use for the reflected test packet.
When the Session-Reflector supports DSCP and ECN Testing mode it uses
R-DSCP-ECN field of the received test packet to construct the
reflected test packet according to the following procedure
o the R-DSCP field MUST be used as six (least-significant) bits of
the Differentiated Service field of the reflected test packet;
o the R-ECN field MAY be used as the two bits of the ECN field of
the reflected test packet.
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0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| R-DSCP | R-ECN |
+---+---+---+---+---+---+---+---+
Figure 1: Sender DSCP and ECN field format
Formats of the test packet transmitted by the Session-Sender in
unauthenticated, authenticated and encrypted modes been defined in
Section 4.1.2 [RFC4656]. For the Session-Sender that supports DSCP
and ECN Testing these formats are displayed in Figure 2 and Figure 3.
For unauthenticated mode:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | R-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Session-Sender test packet format with DSCP and ECN Testing
in unauthenticated mode
Neither Session-Reflector, nor Session-Sender in the DSCP and ECN
Testing mode analyze, nor act on ECN value of the received TWAMP test
packet and therefore ignore congestion indications from the network.
It is expected that sending rates are low enough, as TWAMP deployment
experience had demonstrated since TWAMP base RFC 5357 publication in
2008, that ignoring these congestion indications will not
significantly contribute to network congestion.
For authenticated and encrypted modes:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | R-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (5 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Session-Sender test packet format with DSCP and ECN Testing
in authenticated or encrypted modes
2.2.2. Combining DSCP and ECN Testing and Monitoring extensions
[RFC7750] defined DSCP and ECN Monitoring extension. Using testing
and monitoring modes in the same test session allows test DSCP in
forward and reverse directions because Session-Reflector returns
received DSCP and ECN values in S-DSCP-ECN field in the reflected
test packet.
2.2.3. DSCP and ECN Testing with RFC 6038 extensions
[RFC6038] defined two extensions to TWAMP. First, to ensure that
Session-Sender and Session-Reflector exchange TWAMP-Test packets of
equal size. Second, to specify number of octets to be reflected by
Session-Reflector. If DSCP and ECN Testing and Symmetrical Size and/
or Reflects Octets modes are being negotiated between Server and
Control-Client in Unauthenticated mode, then, because R-DSCP-ECN
field increases size of unauthenticated Session-Sender packet by 4
octets, the Padding Length value SHOULD be >= 26 octets to allow for
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the truncation process that TWAMP recommends in Section 4.2.1 of
[RFC5357].
If DSCP and ECN Testing mode to be used in combination with
Symmetrical Size [RFC6038] and DSCP and ECN Monitoring [RFC7750]
modes, then the Padding Length value SHOULD be >= 27 octets to allow
the truncation process that TWAMP recommends in Section 4.2.1 of
[RFC5357].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | R-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (26 octets) |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+ +
| |
. .
. Packet Padding .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Session-Sender test packet format with DSCP and ECN Testing
and Symmetrical Test Packet in unauthenticated mode
2.2.4. Consideration for TWAMP Light mode
Appendix I of [RFC5357] does not explicitly state how the value of
the Type-P Descriptor is synchronized between Session-Sender and
Session-Reflector and whether different values are considered as
error condition and should be reported.
In order to test DSCP over round-trip path between Session-Sender and
Session-Reflector it is sufficient that Session-Reflector uses
received DSCP value for the reflected test packet. If the Session-
Reflector supports both testing and monitoring of DSCP, then TWAMP
Light mode MAY be used to test DSCP in forward and reverse
directions.
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3. IANA Considerations
The TWAMP-Modes registry defined in [RFC5618].
IANA is requested to reserve a new DSCP and ECN Testing Capability as
follows:
+-----+-----------------------+----------------------+--------------+
| Bit | Description | Semantics Definition | Reference |
+-----+-----------------------+----------------------+--------------+
| TBA | DSCP and ECN Testing | Section 2 | This |
| | Capability | | document |
+-----+-----------------------+----------------------+--------------+
Table 1: New Type-P Descriptor Testing Capability
4. Security Considerations
Testing of DSCP and ECN does not appear to introduce any additional
security threat to hosts that communicate with TWAMP as defined in
[RFC5357], and existing extensions [RFC6038]. Sections such as 3.2,
4., 4.1.2, 4.2, and 4.2.1 of [RFC5357] discuss unauthenticated,
authenticated, and encrypted modes in varying degrees of detail. The
security considerations that apply to any active measurement of live
networks are relevant here as well. See the Security Considerations
sections in [RFC4656], [RFC5357], and [RFC7750].
5. Acknowledgments
TBD
6. References
6.1. 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>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<http://www.rfc-editor.org/info/rfc2474>.
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[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<http://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<http://www.rfc-editor.org/info/rfc5357>.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
DOI 10.17487/RFC5618, August 2009,
<http://www.rfc-editor.org/info/rfc5618>.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
<http://www.rfc-editor.org/info/rfc6038>.
[RFC7750] Hedin, J., Mirsky, G., and S. Baillargeon, "Differentiated
Service Code Point and Explicit Congestion Notification
Monitoring in the Two-Way Active Measurement Protocol
(TWAMP)", RFC 7750, DOI 10.17487/RFC7750, February 2016,
<http://www.rfc-editor.org/info/rfc7750>.
6.2. Informative References
[RFC3260] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002,
<http://www.rfc-editor.org/info/rfc3260>.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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Steve Baillargeon
Ericsson
Email: steve.baillargeon@ericsson.com
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