Network Working Group A. Morton
Internet-Draft L. Ciavattone
Updates: 5357 (if approved) AT&T Labs
Intended status: Standards Track February 28, 2010
Expires: September 1, 2010
TWAMP Reflect Octets and Symmetrical Size Features
draft-ietf-ippm-twamp-reflect-octets-04
Abstract
The IETF has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol. This memo describes two
closely-related features for TWAMP: an optional capability where the
responder host returns some of the command octets or padding octets
to the controller, and an optional sender packet format that ensures
equal 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].
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 1, 2010.
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Copyright Notice
Copyright (c) 2010 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
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This document may contain material from IETF Documents or IETF
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Without obtaining an adequate license from the person(s) controlling
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not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3
3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 4
3.1. Connection Setup with New Features . . . . . . . . . . . . 4
3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 5
3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 7
3.4. Additional considerations . . . . . . . . . . . . . . . . 8
4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 9
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 9
4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 9
4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 9
4.1.3. Reflect Octets: Interaction with Padding Truncation . 11
4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 12
4.1.5. Symmetrical Size AND Reflect Octets:
Session-Sender Packet Format . . . . . . . . . . . . . 12
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 13
4.2.1. Reflect Octets: Session-Reflector Packet Format
and Contents . . . . . . . . . . . . . . . . . . . . . 14
4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 15
4.2.3. Symmetrical Size AND Reflect Octets:
Session-Sender Packet Format . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 16
6.2. Registry Management . . . . . . . . . . . . . . . . . . . 16
6.3. Experimental Numbers . . . . . . . . . . . . . . . . . . . 16
6.4. Registry Contents . . . . . . . . . . . . . . . . . . . . 16
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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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 two closely-related features for TWAMP.
One is 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 memo also adds an OPTIONAL capability to assure that reflected
test packets are the same size in both directions of transmission.
This is accomplished by specifying a new TWAMP-Test Session-Sender
packet format.
This memo and TWAMP is intended to be an update to [RFC5357] when
published. It is not required to implement the features described in
this memo to claim compliance with [RFC5357].
2. Purpose and Scope
The purpose of this memo is to define two OPTIONAL closely-related
features for TWAMP [RFC5357]. The features enhance the TWAMP
responder's capabilities to perform simple operations on control and
test packets: the reflection of octets or padding and symmetrical
sizes of fields in the TWAMP-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 will be used in each direction.
The scope of the memo is currently limited to specifications of the
following features:
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o Reflect Octets: the capability of the Server/Session-Reflector to
reflect specific octets back to the Client/Session-Sender.
o Symmetrical Size: the capability to ensure that TWAMP-Test
protocol uses the same packet size in both directions through
support of a new TWAMP-Test Session-Sender test packet format in
both the Session-Sender and the Session-Reflector. Only the
Session-Sender test packet format is new.
Extension of the modes of operation through assignment of two new
values in the Mode Field (see section 3.1 of[RFC4656] for the format
of the Server Greeting message), while retaining backward
compatibility with the core TWAMP [RFC5357] implementations. The two
new values correspond to the two features defined in this memo.
When the Server and Control-Client have agreed to use the Reflect
Octets mode during control connection setup, then the Control-Client,
the Server, the Session-Sender, and the Session-Reflector MUST all
conform to the requirements of that mode, as identified below.
When the Server and Control-Client have agreed to use the Symmetrical
Size mode during control connection setup, then the Control-Client,
the Server, the Session-Sender, and the Session-Reflector MUST all
conform to the requirements of that mode, as identified below.
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 two
such extensions.
3.1. Connection Setup with New Features
TWAMP connection establishment follows the procedure defined in
section 3.1 of [RFC4656] and section 3.1 of [RFC5357]. The new
features require 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 support the new
Session-Sender packet format in TWAMP-Test Protocol. With this added
feature, the complete set of TWAMP Modes Field bit positions and
values would be as follows:
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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, RFC5681, Section 3.1
Encrypted CONTROL
zzz Individual Session RFC????, Section 3.1
Control
--------------------------------------------------------
xxx Reflect Octets new bit position (X)
Capability
yyy Symmetrical Size new bit position (Y)
Sender Test Packet Format
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
[RFC5618], bit position 3 allows unauthenticated TWAMP Test protocol
to be used with encryption on the TWAMP-Control protocol in a mixed
mode of operation.
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 either of these modes (or
both) if desired.
>>>IANA: change xxx, yyy, X, and Y to the assigned values <<<
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. Reflect Octets: 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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Schedule Slots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. ... Many fields (66 octets) not shown ... .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding Length (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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, following
the definitions of the two new fields that follow the Type-P
Descriptor.
Note that the number of padding octets appended to the Session-
Reflector's test packet depends on support for 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
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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 the RECOMMENDED truncation process in TWAMP section
4.2.1 [RFC5357].
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 the RECOMMENDED truncation process in TWAMP section
4.2.1 [RFC5357].
3.3. Reflect Octets: 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) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
When supporting the RECOMMENDED truncation process in TWAMP section
4.2.1 [RFC5357], 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.
With the publication of this memo as an RFC, the last 7 bit positions
of the Modes 32-bit Field are used. A Control-Client conforming to
this extension of [RFC5357] MAY ignore the values in the higher bits
of the Modes Field, or it MAY support other features that are
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communicated in those bit positions. The other bits are available
for future protocol extensions.
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. Reflect Octets: 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. Reflect Octets: Interaction with Padding Truncation
When the Reflect Octets mode is selected, and the RECOMMENDED
truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the
Session-Sender MUST anticipate a minimum padding required to achieve
equal size test packets in both directions. The amount of padding
needed to achieve symmetrical packet size depends on BOTH the
security mode (Unauthenticated/Authenticated/Encrypted) and whether
the Reflect Octets mode is selected simultaneously.
When using the RECOMMENDED truncation process in TWAMP section 4.2.1
[RFC5357] alone, 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
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RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the
Session-Sender MUST append at least 27 octets of padding plus the
"Length of the padding to reflect" octets when 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.
4.1.4. Symmetrical Size: Session-Sender Packet Format
When the Symmetrical Size mode is selected, the Session-Sender SHALL
use the following TWAMP-Test Packet Format in Unauthenticated mode:
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 (27 octets) |
| |
| |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+ +
. .
. Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This feature REQUIRES only a new Session-Sender test packet format,
the Session-Reflector test packet format is unchanged.
4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet
Format
When BOTH the Symmetrical Size mode and the Reflect Octets mode are
selected, the Session-Sender SHALL use the following TWAMP-Test
Packet Format in Unauthenticated mode:
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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 (27 octets) |
| |
| |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+ +
| Packet Padding (to be reflected) |
. (length in octets specified in command) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this combined mode, the Packet Padding to be reflected follows the
27 MBZ octets. In Authenticated or Encrypted modes, the Packet
Padding to be reflected follows the 56 MBZ octets.
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 Symmetrical Size mode: The Session-Reflector MUST operate using
the Session_Reflector Packet Format defined in section 4.1.4,
where the Padding Octets are separated from the information
fields.
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4.2.1. Reflect Octets: Session-Reflector Packet Format and Contents
The Reflect Padding feature re-designates the packet padding field,
as shown below. When the Reflect Octets mode is selected, the
Session-Sender SHALL use the following TWAMP-Test Packet Format in
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 | 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.
When simultaneously using the RECOMMENDED truncation process in TWAMP
section 4.2.1 [RFC5357] 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
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the highest number octets are discarded, and the test packet length
equals the Session-Sender's packet length. When using the
RECOMMENDED truncation process, 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).
4.2.2. Symmetrical Size: Session-Reflector Packet Format
When Symmetrical Size mode is selected, the Session-Sender packet
formats for unauthenticated and authenticated/encrypted modes are
identical to the core TWAMP specification, section 4.2.1 of
[RFC5357]. Thus, the Session-Reflector test packet format is
unchanged.
The Session-Reflector MUST construct its test packet using the
information in the Session-Sender's test packet. The length of the
Session-Reflector's test packet SHALL equal the length of the
Session-Sender's test packet.
4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet
Format
When BOTH the Symmetrical Size mode and the Reflect Octets mode are
selected, the Session-Reflector MUST operate using the
Session_Reflector Packet Format defined in section 4.1.5, where the
Padding Octets are separated from the information fields, and the
Padding to be Reflected field precedes the Additional Padding.
The Session-Reflector SHALL use the same TWAMP-Test Packet Format as
specified in section 4.2.1 above.
5. 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].
6. IANA Considerations
This memo adds two modes to the IANA registry for the TWAMP Modes
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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 [RFC5618]).
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.
6.2. Registry Management
This registry must be updated only by "IETF Consensus" as specified
in [RFC5226](an RFC documenting registry use that is approved by the
IESG).
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:
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, RFC5618, Section 3.1 (3)
Auth. CONTROL
--------------------------------------------------------
xxx Reflect Octets this memo, section 3.1
Capability new bit position (X)
yyy Symmetrical Size this memo, section 3.1
Sender Test Packet Format new bit position (Y)
The suggested values are
X=5, xxx=32
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Y=6, yyy=64
7. Acknowledgements
The authors would like to thank Walt Steverson and Stina Ross for
helpful review and comments.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
August 2009.
8.2. Informative References
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/
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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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