Network Working Group A. Morton
Internet-Draft L. Ciavattone
Intended status: Standards Track AT&T Labs
Expires: January 7, 2009 July 6, 2008
TWAMP Reflect Padding Feature
draft-morton-ippm-twamp-reflect-padding-00
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Abstract
The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol. This memo describes a proposed feature for
TWAMP, intended for discussion in the IP Performance Metrics WG. The
feature gives the reflector the ability to return some of the packet
padding bits to the sender.
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 RFC 2119 [RFC2119].
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3
3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 3
3.1. Connection Setup with Reflect Padding Feature . . . . . . 4
3.2. Request-TW-Session Packet Format . . . . . . . . . . . . . 5
3.3. Accept Session Packet Format . . . . . . . . . . . . . . . 5
3.4. Additional considerations . . . . . . . . . . . . . . . . 6
4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 6
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 7
4.1.2. Packet Format and Content . . . . . . . . . . . . . . 7
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 9
6.2. Registry Management . . . . . . . . . . . . . . . . . . . 9
6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 9
6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12
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1. Introduction
The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol [I-D.ietf-ippm-twamp], which is an extension to
the One-way Active Measurement Protocol, OWAMP [RFC4656].
This memo describes a new proposed feature for TWAMP, so it can be
discussed and interest to take-up the feature assessed. This feature
adds the capability for the Session-Reflector to return a limited
number of unassigned (padding) bits to the Server/Session-Sender.
With this capability, the Control-Client/Session-Sender can
information it deems useful and have the assurance that the
corresponding test packet will contain the information when it is
returned.
The relationship between this memo and TWAMP is intended to be an
update to the TWAMP RFC when published.
2. Purpose and Scope
The purpose of this memo is to describe an additional function and
feature for TWAMP [I-D.ietf-ippm-twamp]. The feature needs a clear
description so it can be discussed and (hopefully) adopted in the IP
Performance Metrics Charter.
The scope of the memo is currently limited to specifications of the
following feature:
1. Extension of the modes of operation through assignment of new
values in the Mode field (see section 3.1 of [RFC4656]), while
retaining backward compatibility with TWAMP [I-D.ietf-ippm-twamp]
implementations. These values identify the ability of the
Server/Session-Reflector to reflect specific octets of Packet
Padding back to the Client/Sender. The motivation for this
extension is to permit the Sender to tag packets with a index for
simplified identification, or other uses.
(other items may be added)
When new features are discussed and reach consensus, they may become
chartered work items in IETF IPPM (and may appear in a different
memo).
3. TWAMP Control Extensions
TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
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and provides two-way measurement capability. TWAMP
[I-D.ietf-ippm-twamp] uses the Mode field to identify and select
specific communication capabilities, and this field is a recognized
extension mechanism. The following sections describe one such
extension.
3.1. Connection Setup with Reflect Padding Feature
TWAMP connection establishment follows the procedure defined in
section 3.1 of [RFC4656]. The Reflect Padding feature requires two
new bit positions (and values) to identify the ability of the Server/
Session-Reflector to reflect specific octets of Packet Padding back
to the Client/Sender. With this added feature, the complete set of
TWAMP mode values would be as follows:
Value Description Reference/Explanation
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
xx Reflect Padding new bit position (X)
Capability
yyy Reflect & Operate new bit position (Y)
on Padding Bits
In the original OWAMP mode field, setting bit positions 0, 1 or 2
indicated the security mode of the Control protocol, and the Test
protocol inherited the same mode (see section 4 of [RFC4656]). In
the [I-D.morton-ippm-more-twamp] bit positions (3, 4 or 5)
discontinue the inheritance of the security mode in the Test
protocol.
The Server sets one or both of the new bit positions (possibly 6
and/or 7) in the Server Greeting message to indicate its capabilities
and willingness to operate in these modes if desired.
If the Control-Client intends to operate all test sessions under this
control connection using one of the new modes, it MUST set one of
mode bits corresponding to that mode in the Setup Response message.
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3.2. Request-TW-Session Packet Format
The bits designated for the Reflect Padding feature in the Request-
TW-Session command are as shown in the packet format below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Schedule Slots |
.
. ... Many fields not shown ...
.
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type-P Descriptor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (to be reflected) | MBZ (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (to be reflected)" field SHALL be 2 octets long,
as shown.
3.3. Accept Session Packet Format
The bits designated for the Reflect Padding feature in the Accept
Session command are as shown in the packet format below.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accept | MBZ | Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
| |
| SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding (to be reflected) | MBZ (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (to be reflected)" field SHALL be 2 octets long,
as shown.
3.4. Additional considerations
The value of the Modes field sent by the Server (in the Server
Greeting message) is the bit-wise OR of the mode values that it is
willing to support during this session.
If BOTH the above modes are adopted, the last eight bits of the Modes
32-bit field are used. The first 24 bits MUST be zero. A client
conforming to this version of the specification MUST ignore the
values in the first 24 bits of the Modes value. (This way, the bits
are available for future protocol extensions.)
Other ways in which TWAMP extends OWAMP are described in
[I-D.ietf-ippm-twamp].
4. Extended TWAMP Test
The TWAMP test protocol is similar to the OWAMP [RFC4656] test
protocol with the exception that the Session-Reflector transmits test
packets to the Session-Sender in response to each test packet it
receives. TWAMP [I-D.ietf-ippm-twamp] section 4 defines two
additional test packet formats for packets transmitted by the
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Session-Reflector. The appropriate format depends on the security
mode chosen. This feature utilizes some of the bits within each test
packet format.
4.1. Sender Behavior
This section describes extensions to the behavior of the TWAMP
Session-Sender.
4.1.1. Packet Timings
The Send Schedule is not utilized in TWAMP, and this is unchanged in
this memo.
4.1.2. Packet Format and Content
The Session-Sender packet format and content follow the same
procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as
indicated in section 4.1.2 of TWAMP [I-D.ietf-ippm-twamp]).
The Reflect Padding feature re-designates the packet padding field,
as shown below 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 | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ | Length (2 oct) | Ext ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet Padding (to be reflected) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional Packet Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (to be reflected)" field MAY be as long as 12
octets, as shown. IF the test packet length is truncated within this
field, THEN ALL packet padding MUST be reflected by Session-
Reflectors using this feature.
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4.2. Reflector Behavior
The TWAMP Reflector follows the procedures and guidelines in section
4.2 of [I-D.ietf-ippm-twamp], with the following additional
functions:
o bits in the packet padding field of the Session-Sender's test
packet MUST be inserted in the Session-Reflector's test packet.
The Reflect Padding feature re-designates the packet padding field,
as shown below 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 | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | Length (2 oct) | Ext ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet Padding (from Session-Sender) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional Packet Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (to be reflected)" field MAY be as long as 12
octets, as shown. IF the test packet length is truncated within this
field, THEN ALL packet padding MUST be reflected by Session-
Reflectors using this feature.
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5. Security Considerations
These extended modes of operation permit stronger integrity
protection on the TWAMP-Control protocol while simultaneously
emphasizing accuracy or efficiency on the TWAMP-Test protocol, thus
enhancing overall security when compared to the previous options.
The security considerations that apply to any active measurement of
live networks are relevant here as well. See [RFC4656] and
[I-D.ietf-ippm-twamp].
6. IANA Considerations
This memo adds two mode combinations to the IANA registry for the
TWAMP Mode field, and describes behavior when the new modes are used.
This field is a recognized extension mechanism for TWAMP.
6.1. Registry Specification
IANA has created a TWAMP-Modes registry (as requested in
[I-D.morton-ippm-more-twamp]). TWAMP-Modes are specified in TWAMP
Server Greeting messages and Set-up Response messages, as described
in section 3.1 of [I-D.ietf-ippm-twamp], consistent with section 3.1
of [RFC4656], and extended by this memo. Modes are indicated by
setting bits in the 32-bit Modes field. Thus, this registry can
contain a total of 32 possible values.
6.2. Registry Management
Because the Modes registry can contain only thirty-two values, and
because TWAMP is an IETF protocol, this registry must be updated only
by "IETF Consensus" as specified in [RFC2434](an RFC documenting
registry use that is approved by the IESG). For the Modes registry,
we expect that new features will be assigned using monotonically
increasing bit positions and in the range [0-31] and the
corresponding values, unless there is a good reason to do otherwise.
6.3. Experimental Numbers
No experimental values are currently assigned for the Modes Registry.
6.4. Registry Contents
TWAMP Modes Registry is recommended to be augmented as follows:
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Value Description Semantics Definition
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
xx Reflect Padding this memo, section 3.1
Capability new bit position (X)
yyy Reflect & Operate this memo, section 3.1
on Padding Bits new bit position (Y)
7. Acknowledgements
The authors would like to thank future readers for helpful review and
comments.
8. References
8.1. Normative References
[I-D.ietf-ippm-twamp]
Babiarz, J., "A Two-way Active Measurement Protocol
(TWAMP)", draft-ietf-ippm-twamp-08 (work in progress),
June 2008.
[I-D.morton-ippm-more-twamp]
Morton, A. and K. Hedayat, "More Features for TWAMP",
draft-morton-ippm-more-twamp-00 (work in progress),
February 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
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[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
8.2. Informative References
[x] "".
Authors' Addresses
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
URI: http://home.comcast.net/~acmacm/
Len Ciavattone
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1239
Fax:
Email: lencia@att.com
URI:
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