Internet DRAFT - draft-ietf-ippm-type-p-monitor
draft-ietf-ippm-type-p-monitor
Network Working Group J. Hedin
Internet-Draft G. Mirsky
Updates: 5357 (if approved) S. Baillargeon
Intended status: Standards Track Ericsson
Expires: May 7, 2016 November 4, 2015
Differentiated Service Code Point and Explicit Congestion Notification
Monitoring in Two-Way Active Measurement Protocol (TWAMP)
draft-ietf-ippm-type-p-monitor-03
Abstract
This document describes an optional extension for Two-Way Active
Measurement Protocol (TWAMP) allowing the monitoring of the
Differentiated Service Code Point and Explicit Congestion
Notification fields with the TWAMP-Test protocol.
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 May 7, 2016.
Copyright Notice
Copyright (c) 2015 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
Hedin, et al. Expires May 7, 2016 [Page 1]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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 Monitor DSCP and ECN . . . . . . 3
2.2. TWAMP-Test Extension . . . . . . . . . . . . . . . . . . 4
2.2.1. Session-Reflector Packet Format for DSCP and ECN
Monitoring . . . . . . . . . . . . . . . . . . . . . 4
2.2.2. DSCP and ECN Monitoring with RFC 6038 extensions . . 7
2.2.3. Consideration for TWAMP Light mode . . . . . . . . . 8
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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. However
the TWAMP-Test protocol does not specify any methods to determine or
report when the DSCP value has changed or is different than expected
in the forward or reverse direction. Re-marking the DSCP (changing
its original value) in IP networks is possible and often accomplished
by a Differentiated Services policy configured on a single node along
the IP path. In many cases, a change of the DSCP value indicates an
unintentional or erroneous behavior. At best, the Session-Sender can
detect a change of the DSCP reverse direction assuming such change is
actually detectable.
This document describes an OPTIONAL feature for TWAMP. It is called
the DSCP and ECN Monitoring. It allows the Session-Sender to know
the actual DSCP value received at the Session-Reflector. Furthermore
Hedin, et al. Expires May 7, 2016 [Page 2]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
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 Measurement
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 return
value of received DSCP and ECN values back to a Session-Sender, and
to support the new Session-Reflector packet format in the TWAMP-Test
protocol. See the Section 3 for details on the assigned bit
position.
2.1. Setting Up Connection to Monitor DSCP and ECN
The Server sets the DSCP and ECN Monitoring 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 monitor
DSCP and ECN on some or all test sessions invoked with this control
connection, it MUST set the DSCP and ECN Monitoring flag in the Modes
field in the Setup Response message.
Hedin, et al. Expires May 7, 2016 [Page 3]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
2.2. TWAMP-Test Extension
Monitoring of DSCP and ECN requires support by the Session-Reflector
and changes the test packet format in all the original
(unauthenticated, authenticated and encrypted) modes. Monitoring of
DSCP and ECN does not alter the Session-Sender test packet format but
certain considerations must be taken when and if this mode is
accepted in combination with Symmetrical Size mode [RFC6038].
2.2.1. Session-Reflector Packet Format for DSCP and ECN Monitoring
When the Session-Reflector supports DSCP and ECN Monitoring it
constructs the Sender DSCP and ECN (S-DSCP-ECN) field, presented in
Figure 1, for each test packet it sends to Session-Sender according
to the following procedure:
o the six (least-significant) bits of the Differentiated Service
field MUST be copied from received Session-Sender test packet into
Sender DSCP (S-DSCP) field;
o the two bits of the ECN field MUST be copied from received
Session-Sender test packet into Sender ECN (S-ECN) field.
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| S-DSCP | S-ECN |
+---+---+---+---+---+---+---+---+
Figure 1: Sender DSCP and ECN field format
Formats of the test packet transmitted by the Session-Reflector in
unauthenticated, authenticated and encrypted modes been defined in
Section 4.2.1 [RFC5357]. For the Session-Reflector that supports
DSCP and ECN Monitoring these formats are displayed in Figure 2 and
Figure 3.
For unauthenticated mode:
Hedin, et al. Expires May 7, 2016 [Page 4]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
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 | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Session-Reflector test packet format with DSCP and ECN
Monitoring in unauthenticated mode
The DSCP and ECN values (part of the Type-P Descriptor [RFC4656]) can
be provisioned through TWAMP-Control or by other means (CLI or
Central Controller). The DSCP and ECN values are often copied into
reflected test packets with current TWAMP implementations without
TWAMP-Control protocol. With DSCP and ECN Monitoring Extension, the
Session-Reflector handles DSCP as following:
o the Session-Reflector MUST extract the DSCP and ECN values from
the received packet and MUST populate with them S-DSCP-ECN field
of the corresponding reflected packet;
o the Session-Reflector MUST transmit each reflected test packet
with DSCP set to the provisioned value;
o if the provisioned DSCP value is not known (e.g. TWAMP Light),
the choice of the DSCP is implementation specific. For instance,
Session-Reflector MAY copy the DSCP value from the received test
Hedin, et al. Expires May 7, 2016 [Page 5]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
packet and set it as DSCP in a reflected packet. Alternatively
Session-Reflector MAY set DSCP value to CS0 (zero) [RFC2474];
o if the provisioned ECN value is not known, ECN SHOULD be set to
Not-ECT codepoint value [RFC3168]. Otherwise, the provisioned ECN
value for the session SHALL be used.
A Session-Reflector in the DSCP and ECN Monitoring mode does not
analyze, nor acts on ECN value of the received TWAMP test packet and
therefore ignores 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:
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 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Hedin, et al. Expires May 7, 2016 [Page 6]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
| Sender Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (14 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Session-Reflector test packet format with DSCP and ECN
Monitoring in authenticated or encrypted modes
2.2.2. DSCP and ECN Monitoring 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 Monitoring and Symmetrical Size
and/or Reflects Octets modes are being negotiated between Server and
Control-Client in Unauthenticated mode, then, because Sender DSCP and
Sender ECN increase size of unauthenticated Session-Reflector packet
by 4 octets, the Padding Length value SHOULD be >= 28 octets to allow
for the truncation process that TWAMP recommends in Section 4.2.1 of
[RFC5357].
Hedin, et al. Expires May 7, 2016 [Page 7]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
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 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (28 octets) |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. .
. Packet Padding .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Session-Sender test packet format with DSCP and ECN
Monitoring and Symmetrical Test Packet in unauthenticated mode
2.2.3. 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. We assume that by some means
the Session-Sender and the Session-Reflector of the given TWAMP-Test
session been informed to use the same DSCP value. Same means, i.e.
configuration, could be used to inform Session-Reflector to support
DSCP and ECN Monitoring mode by copying data from received TWAMP test
packets. Then Session-Sender may be informed to use Sender DSCP and
ECN field in reflected TWAMP test packet.
3. IANA Considerations
The TWAMP-Modes registry defined in [RFC5618].
IANA is requested to reserve a new DSCP and ECN Monitoring Capability
as follows:
Hedin, et al. Expires May 7, 2016 [Page 8]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
+-----+------------------------+---------------------+--------------+
| Bit | Description | Semantics | Reference |
| | | Definition | |
+-----+------------------------+---------------------+--------------+
| TBA | DSCP and ECN | Section 2 | This |
| | Monitoring Capability | | document |
+-----+------------------------+---------------------+--------------+
Table 1: New Type-P Descriptor Monitoring Capability
4. Security Considerations
Monitoring 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] and [RFC5357].
5. Acknowledgements
Authors greatly appreciate thorough review and thoughtful comments by
Bill Cerveny, Christofer Flinta and Samita Chakrabarti.
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>.
[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>.
Hedin, et al. Expires May 7, 2016 [Page 9]
Internet-Draft DSCP and ECN Monitoring in TWAMP November 2015
[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>.
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
Jonas Hedin
Ericsson
Email: jonas.hedin@ericsson.com
Greg Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
Steve Baillargeon
Ericsson
Email: steve.baillargeon@ericsson.com
Hedin, et al. Expires May 7, 2016 [Page 10]
