Network Working Group A. Morton
Internet-Draft L. Ciavattone
Intended status: Standards Track AT&T Labs
Expires: January 14, 2010 July 13, 2009
TWAMP Reflect Octets Feature
draft-ietf-ippm-twamp-reflect-octets-02
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Abstract
The IETF has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol. This memo describes a new
feature for TWAMP: an optional capability where the responder host
returns some of the command octets or padding octets to the
controller, and/or ensures that the same test packet sizes are used
in both directions.
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 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 4
3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 5
3.1. Connection Setup with Reflect Padding Feature . . . . . . 5
3.2. Request-TW-Session Packet Format . . . . . . . . . . . . . 6
3.3. Accept Session Packet Format . . . . . . . . . . . . . . . 8
3.4. Additional considerations . . . . . . . . . . . . . . . . 8
4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 9
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 9
4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 9
4.1.2. Packet Formats and Contents . . . . . . . . . . . . . 9
4.1.3. Padding Truncation . . . . . . . . . . . . . . . . . . 11
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 12
4.2.1. Packet Format and Contents . . . . . . . . . . . . . . 12
4.2.2. Padding Truncation . . . . . . . . . . . . . . . . . . 13
5. Possible Alternative . . . . . . . . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. Registry Specification . . . . . . . . . . . . . . . . . . 17
7.2. Registry Management . . . . . . . . . . . . . . . . . . . 17
7.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 17
7.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
The IETF has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol [RFC5357]. TWAMP is an
extension of the One-way Active Measurement Protocol, OWAMP
[RFC4656]. The TWAMP specification gathered wide review as it
approached completion, and the by-products were several
recommendations for new features in TWAMP. There are a growing
number TWAMP implementations at present, and wide-spread usage is
expected. There are even devices that are designed to test
implementations for protocol compliance.
This memo describes a new feature for TWAMP. This feature adds the
OPTIONAL capability for the responder host to return a limited number
of unassigned (padding) octets to the Control-Client or Session-
Sender entities. With this capability, the Control-Client or
Session-Sender can embed octets of information it deems useful and
have the assurance that the corresponding reply/test packet will
contain that information when it is reflected and returned (by the
Server or Session-Reflector. The feature also adds the Session-
Reflector capability to assure that reflected test packets SHALL have
their padding octets truncated, so that TWAMP-Test protocol uses the
same packet size in both directions of transmission.
The relationship between this memo and TWAMP is intended to be an
update to [RFC5357] when published.
2. Purpose and Scope
The purpose of this memo is to describe a new feature for TWAMP
[RFC5357]. The feature enhances the TWAMP responder's capabilities
to perform simple operations on control and test packets: the
reflection of octets or padding and the guaranteed truncation of
padding to compensate for the different sizes of TWAMP fields in the
test packets. Motivations include permitting the controller host to
tag packets with an index for simplified identification, and/or
assert that the same size test packets MUST be used in each
direction.
The scope of the memo is currently limited to specifications of the
following feature:
o Extension of the modes of operation through assignment of new
values in the Mode Field (see section 3.1 [RFC4656] for the format
of the Server Greeting message), while retaining backward
compatibility with the core TWAMP [RFC5357] implementations.
These two values identify the ability of the Server/
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Session-Reflector to reflect specific octets back to the Client/
Session-Sender, and/or to truncate padding octets and ensure that
TWAMP-Test protocol uses the same packet size in both directions.
3. TWAMP Control Extensions
TWAMP-Control protocol [RFC5357] uses the Modes 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] and section 3.1 of [RFC5357]. The new
feature requires two new bit positions (and values) to identify the
ability of the Server/Session-Reflector to reflect specific octets
back to the Control-Client/Session-Sender, and to truncate padding
octets when required. With this added feature, the complete set of
TWAMP Modes Field bit positions and 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-ietf-more-twamp (3)
Encrypted CONTROL
--------------------------------------------------------
xxx Reflect Octets new bit position (X)
Capability
yyy Truncate Padding new bit position (Y)
Capability
In the original OWAMP Modes 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 memo [I-D.ietf-ippm-more-twamp], bit position 3 allows
unauthenticated TWAMP Test protocol to be used with encryption on the
TWAMP-Control protocol.
The Server sets one or both of the new bit positions (X and Y) in the
Modes Field of the Server Greeting message to indicate its
capabilities and willingness to operate in these modes if desired.
>>>IANA: change X and Y to the assigned values <<<
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If the Control-Client intends to operate all test sessions invoked
with this control connection using one or both of the new modes, it
MUST set the Modes Field bit corresponding to that function in the
Setup Response message.
3.2. Request-TW-Session Packet Format
The bits designated for the Reflect Octets 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 (66 octets) not shown ... .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Time, (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timeout, (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type-P Descriptor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Octets to be reflected | Length of padding to reflect |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Padding Length" Field *continues* to specify the number of
padding octets that the Session-Sender will append to ALL TWAMP-Test
packets associated with this test session. See below for
considerations on the minimum length of the padding octets,
especially when complying with the options described in this memo,
following the definitions of the two new fields that follow the
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Type-P Descriptor.
Note that the number of padding octets appended to the Session-
Reflector's test packet depends on support for the OPTIONAL Truncate
Padding mode, or the RECOMMENDED truncation process in TWAMP section
4.2.1 [RFC5357].
The "Octets to be reflected" Field SHALL be 2 octets long, as shown
and contains the octets that the Server MUST reflect in the Accept
Session message as specified below.
The "Length of padding to reflect" Field SHALL be 2 octets long, and
contain an unsigned binary value in units of octets. This field
communicates the length of the padding in the TWAMP-Test Packet that
the Session-Sender expects to be reflected, and the length of octets
that the Session-Reflector SHALL return in include in its TWAMP-Test
packet format (see section 4.2). By including this length field in
the Request-TW-Session message, a Server is able to determine if it
can comply with a specific request to reflect padding in the TWAMP-
Test packets, and to arrange for the Session-Reflector processing in
advance.
The "Padding Length" SHOULD be >= 27 octets when specifying a test
session using the Unauthenticated TWAMP-Test mode, to allow for the
RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357].
The "Padding Length" SHOULD be >= 56 octets when specifying a test
session using the Authenticated or Encrypted TWAMP-Test modes, to
allow for the RECOMMENDED truncation process in TWAMP section 4.2.1
[RFC5357].
The "Padding Length" SHALL be > the "Length of padding to reflect"
when specifying a test session using the OPTIONAL Reflect Octets
mode.
The "Padding Length" SHALL be >= 27 + "Length of padding to reflect"
octets when specifying a test session using BOTH the OPTIONAL Reflect
Octets mode and OPTIONAL Truncate Padding mode with the
Unauthenticated TWAMP-Test mode.
The "Padding Length" SHALL be >= 56 + "Length of padding to reflect"
octets when specifying a test session using BOTH the OPTIONAL Reflect
Octets mode and OPTIONAL Truncate Padding mode with the Authenticated
or Encrypted TWAMP-Test modes.
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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.
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) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reflected octets | Server octets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Reflected octets" field SHALL contain the octets from the
Request-TW-Session "Octets to be reflected" Field, and be 2 octets
long, as shown.
The "Server octets" field SHALL contain information that the Server
intends to be returned in the TWAMP-Test packet padding to-be-
reflected Field, OR SHALL be zero, and be 2 octets long, as shown.
Although the Server determines the SID, this field is very long (16
octets) and does not normally appear in TWAMP-Test packets.
In Truncate Padding mode, IF calculations on the Padding lengths
reveal that there are insufficient octets supplied to produce equal-
length Session-Sender and Session-Reflector test packets, then the
Accept Field MUST be set to 3 = some aspect of the request is not
supported.
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.
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Thus, the last six bits of the Modes 32-bit Field are used. A client
conforming to this extension of [RFC5357] MAY ignore the values in
the first 24 bits of the Modes Field, or it MAY support other
features that are communicated in these bit positions. (The first 24
bits are available for future protocol extensions.)
Other ways in which TWAMP extends OWAMP are described in [RFC5357].
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 section 4[RFC5357] defines two additional test
packet formats for packets transmitted by the Session-Reflector. The
appropriate format depends on the security mode chosen. The new
modes specified here utilize some of the padding octets within each
test packet format, or require truncation of those octets depending
on the security mode in use.
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 Formats and Contents
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 [RFC5357]).
The Reflect octets mode re-designates the original TWAMP-Test (and
OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as
shown below for unauthenticated mode:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| Packet Padding (to be reflected) |
. (length in octets specified in command) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (to be reflected)" Field SHALL correspond to the
length of octets specified in the Request-TW-Session "Length of
padding to reflect" Field to this test session. These are the octets
that the Session-Sender expects will be returned by the Session-
Reflector.
The length of the "Additional Packet Padding" Field is the difference
between two fields in the Request-TW-Session command, as follows:
"Additional Packet Padding", in octets =
"Padding Length" - "Length of padding to reflect"
One possible use of the first 4 octets of the "Packet Padding (to be
reflected)" Field is shown 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server octets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Client octets | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Packet Padding (to be reflected) |
. (length in octets specified elsewhere) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example, the "Client octets" and the "Server octets" fields
contain the same information that the Client and Server exchanged in
the Request-TW-Session and Accept-Session messages corresponding to
this specific test session. These octets would be reflected the same
as the rest of the "Packet Padding (to be reflected)" Field.
4.1.3. Padding Truncation
When the Truncate Padding mode is selected and communicated in the
Setup Response message, the Session-Sender MUST anticipate a minimum
padding required to achieve equal size test packets in both
directions. The amount of padding needed depends on BOTH the
security mode (Unauthenticated/Authenticated/Encrypted) and whether
the Reflect Octets mode is selected simultaneously.
When using the Truncate Padding mode, the Session-Sender MUST append
sufficient Packet Padding octets to allow the same IP packet payload
lengths to be used in each direction of transmission (this is usually
desirable). To compensate for the Session-Reflector's larger test
packet format, the Session-Sender MUST append at least 27 octets of
padding in Unauthenticated mode, and at least 56 octets in
Authenticated and Encrypted modes. The sizes of TWAMP Test protocol
packets and the resulting truncated padding to achieve equal packet
sizes in both directions are shown in the table below:
+-------------------+----------------------+---------------------+
| Octets in: | Unauthenticated Mode | Auth/Encrypted Mode |
+-------------------+----------------------+---------------------+
| Reflector Header | 41 | 104 |
| Sender Header | 14 | 48 |
| Truncated Padding | 27 | 56 |
+-------------------+----------------------+---------------------+
TWAMP-Test Padding Trucation
When using the Reflect Octets mode simultaneously with the Truncate
Padding mode, the Session-Sender MUST append at least 27 octets of
padding plus the "Length of the padding to reflect" octets when
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operating in Unauthenticated mode. The Session-Sender MUST append at
least 56 octets of padding plus the "Length of the padding to
reflect" octets when operating in Authenticated and Encrypted modes.
4.2. Reflector Behavior
The TWAMP Reflector follows the procedures and guidelines in section
4.2 of [RFC5357], with the following additional functions:
o Reflect Octets mode: Designated octets in the "Packet Padding (to
be reflected)" field of the Session-Sender's test packet MUST be
included in the Session-Reflector's test packet.
o Truncate Padding mode: Octets in the packet padding field of the
Session-Sender's test packet MUST be truncated so that the length
of the Session-Reflector's test packet equals the length of the
Session-Sender's test packet.
4.2.1. Packet Format and Contents
The Reflect Padding feature re-designates the packet padding field,
as shown below for unauthenticated mode:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | Packet Padding (from Session-Sender) |
+-+-+-+-+-+-+-+-+ +
. .
+ +-+-+-+-+-+-+-+-+
| Packet Padding (from Session-Sender) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| |
. Additional Packet Padding .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Packet Padding (from Session-Sender)" field MUST be the same
octets as the "Packet Padding (to be reflected)" field in the
Session-Sender's test packet, and therefore MUST conform to the
length specified in the Request-TW-Session message.
IF the test packet length is truncated within the padding fields in
conformance with the RECOMMENDED truncation process in TWAMP section
4.2.1 [RFC5357], THEN ALL padding designated to be reflected MUST be
reflected by Session-Reflectors using this feature.
4.2.2. Padding Truncation
Note that the Session-Reflector Test Packet Formats are larger than
the Sender's formats. When the Truncate Padding mode is selected and
communicated in the Setup Response message, the Session-Reflector
must truncate a specific number of padding octets to achieve equal
size test packets in both directions. The number of octets truncated
depends on BOTH the security mode (Unauthenticated/Authenticated/
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Encrypted) and whether the Reflect octets mode is selected
simultaneously.
When using the Truncate Padding mode, the Session-Reflector MUST
truncate exactly 27 octets of padding in Unauthenticated mode, and
exactly 56 octets in Authenticated and Encrypted modes. The Session-
Reflector MAY re-use the Sender's Packet Padding (since the
requirements for padding generation are the same for each), and in
this case the Session-Reflector MUST truncate the padding such that
the highest number octets are discarded.
When simultaneously using the Truncate Padding mode AND Reflect
octets mode, the Session-Reflector MUST reflect the designated octets
from the Session-Sender's test packet in the "Packet Padding (from
Session-Sender)" Field, and MAY re-use additional Packet Padding from
the Session-Sender. The Session-Reflector MUST truncate the padding
such that the highest number octets are discarded, and the test
packet length equals the Session-Sender's packet length.
5. Possible Alternative
If new TWAMP-Test packet formats are defined, the Reflect Octets and
Truncate Padding modes could be folded into one new mode.
It would be possible to obtain even 4 octet boundaries in the revised
format.
It is also possible to simplfy test packet reflection by leaving the
Session-Sender's fields exactly as received, and replacing the
Discard Fill Field with the new time stamps and sequence number
determined by the Session-Reflector.
No calculations on padding are needed, and symmetrical packet size is
ensured for both directions of transmssion.
The "Packet Padding (to be reflected)" Field could contain
information that is TLV encoded, but in general the padding is opaque
to the Session-Reflector.
This Alternative is illustrated for discussion purposes.
New Session-Sender Test Packet Format:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| |
| Discard Fill |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet Padding (to be reflected) |
. (length in octets specified elsewhere) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Discard Fill" octets are discarded at the Session-Reflector.
New Session-Reflector Test Packet format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reflector Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reflector Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reflector's Sending Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | MBZ (3 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Packet Padding (from Session-Sender) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Additional Packet Padding .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6. Security Considerations
These extended modes of operation do not appear to permit any new
attacks on hosts communicating with core TWAMP [RFC5357] ???
The security considerations that apply to any active measurement of
live networks are relevant here as well. See [RFC4656] and
[RFC5357].
7. IANA Considerations
This memo adds two mode combinations to the IANA registry for the
TWAMP Modes Field, and describes behavior when the new modes are
used. This field is a recognized extension mechanism for TWAMP.
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7.1. Registry Specification
IANA has created a TWAMP-Modes registry (as requested in
[I-D.ietf-ippm-more-twamp]). TWAMP-Modes are specified in TWAMP
Server Greeting messages and Set-up Response messages, as described
in section 3.1 of [RFC5357], 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.
7.2. 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.
7.3. Experimental Numbers
No experimental values are currently assigned for the Modes Registry.
7.4. Registry Contents
TWAMP Modes Registry is recommended to be augmented as follows:
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-ietf-more-twamp (3)
Auth. CONTROL
--------------------------------------------------------
xxx Reflect Octets this memo, section 3.1
Capability new bit position (X)
yyy Truncate Padding this memo, section 3.1
Capability new bit position (Y)
The suggested values are
X=4, xxx=16
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Y=5, yyy=32
8. Acknowledgements
The authors would like to thank Walt Steverson for helpful review and
comments.
9. References
9.1. Normative References
[I-D.ietf-ippm-more-twamp]
Morton, A. and K. Hedayat, "More Features for the Two-Way
Active Measurement Protocol - TWAMP",
draft-ietf-ippm-more-twamp-02 (work in progress),
May 2009.
[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.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
9.2. Informative References
[x] "".
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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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