draft-ietf-ippm-twamp-reflect-octets-07.txt   draft-ietf-ippm-twamp-reflect-octets-08.txt 
Network Working Group A. Morton Network Working Group A. Morton
Internet-Draft L. Ciavattone Internet-Draft L. Ciavattone
Updates: 5357 (if approved) AT&T Labs Updates: 5357 (if approved) AT&T Labs
Intended status: Standards Track June 28, 2010 Intended status: Standards Track August 13, 2010
Expires: December 30, 2010 Expires: February 14, 2011
TWAMP Reflect Octets and Symmetrical Size Features TWAMP Reflect Octets and Symmetrical Size Features
draft-ietf-ippm-twamp-reflect-octets-07 draft-ietf-ippm-twamp-reflect-octets-08
Abstract Abstract
This memo describes two closely-related features for the core This memo describes two closely-related features for the core
specification of TWAMP - the Two-Way Active Measurement Protocol: an specification of TWAMP - the Two-Way Active Measurement Protocol: an
optional capability where the responding host returns some of the optional capability where the responding host returns some of the
command octets or padding octets to the sender, and an optional command octets or padding octets to the sender, and an optional
sender packet format that ensures equal test packet sizes are used in sender packet format that ensures equal test packet sizes are used in
both directions. both directions.
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 30, 2010. This Internet-Draft will expire on February 14, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 3, line 13 skipping to change at page 3, line 13
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 4 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 4
3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 5 3. TWAMP Control Extensions . . . . . . . . . . . . . . . . . . . 5
3.1. Connection Setup with New Features . . . . . . . . . . . . 5 3.1. Connection Setup with New Features . . . . . . . . . . . . 5
3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 6 3.2. Reflect Octets: Request-TW-Session Packet Format . . . . . 6
3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 8 3.3. Reflect Octets: Accept Session Packet Format . . . . . . . 8
3.4. Additional considerations . . . . . . . . . . . . . . . . 9 3.4. Additional considerations . . . . . . . . . . . . . . . . 10
4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 9 4. Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 10
4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 9 4.1. Sender Behavior . . . . . . . . . . . . . . . . . . . . . 10
4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 9 4.1.1. Packet Timings . . . . . . . . . . . . . . . . . . . . 10
4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 10 4.1.2. Reflect Octets: Packet Formats and Contents . . . . . 10
4.1.3. Reflect Octets: Interaction with Padding Truncation . 11 4.1.3. Reflect Octets: Interaction with Padding Truncation . 12
4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 12 4.1.4. Symmetrical Size: Session-Sender Packet Format . . . . 13
4.1.5. Symmetrical Size AND Reflect Octets: 4.1.5. Symmetrical Size AND Reflect Octets:
Session-Sender Packet Format . . . . . . . . . . . . . 13 Session-Sender Packet Format . . . . . . . . . . . . . 14
4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 14 4.2. Reflector Behavior . . . . . . . . . . . . . . . . . . . . 15
4.2.1. Reflect Octets: Session-Reflector Packet Format 4.2.1. Reflect Octets: Session-Reflector Packet Format
and Contents . . . . . . . . . . . . . . . . . . . . . 15 and Contents . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 16 4.2.2. Symmetrical Size: Session-Reflector Packet Format . . 17
4.2.3. Symmetrical Size AND Reflect Octets: 4.2.3. Symmetrical Size AND Reflect Octets:
Session-Sender Packet Format . . . . . . . . . . . . . 16 Session-Sender Packet Format . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. Registry Specification . . . . . . . . . . . . . . . . . . 17 6.1. Registry Specification . . . . . . . . . . . . . . . . . . 18
6.2. Registry Contents . . . . . . . . . . . . . . . . . . . . 17 6.2. Registry Contents . . . . . . . . . . . . . . . . . . . . 18
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. Normative References . . . . . . . . . . . . . . . . . . . 18 8.1. Normative References . . . . . . . . . . . . . . . . . . . 19
8.2. Informative References . . . . . . . . . . . . . . . . . . 18 8.2. Informative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
TWAMP - the Two-Way Active Measurement Protocol [RFC5357] is an TWAMP - the Two-Way Active Measurement Protocol [RFC5357] is an
extension of the One-way Active Measurement Protocol, OWAMP extension of the One-way Active Measurement Protocol, OWAMP
[RFC4656]. The TWAMP specification gathered wide review as it [RFC4656]. The TWAMP specification gathered wide review as it
approached completion, and the by-products were several approached completion, and the by-products were several
recommendations for new features in TWAMP. recommendations for new features in TWAMP.
This memo describes two closely-related features for TWAMP. This memo describes two closely-related features for TWAMP.
One is the OPTIONAL capability for the responder host to return a One is the OPTIONAL capability for the responder host to return a
limited number of unassigned (padding) octets to the Control-Client limited number of unassigned (padding) octets to the Control-Client
or Session-Sender entities in both the TWAMP-Control and TWAMP-Test or Session-Sender entities in both the TWAMP-Control and TWAMP-Test
protocols. With this capability, the Control-Client or Session- protocols. With this capability, the Control-Client or Session-
Sender can embed octets of information it deems useful and have the Sender can embed octets of information it deems useful and have the
assurance that the corresponding reply/test packet will contain that assurance that the corresponding reply/test packet will contain that
information when it is reflected and returned (by the Server or information when it is reflected and returned (by the Server or
Session-Reflector. Session-Reflector).
The memo also adds an OPTIONAL capability to assure that reflected The memo also adds an OPTIONAL capability to assure that reflected
test packets are the same size in both directions of transmission. test packets are the same size in both directions of transmission.
This is accomplished by specifying a new TWAMP-Test Session-Sender This is accomplished by specifying a new TWAMP-Test Session-Sender
packet format. packet format. Although TWAMP [RFC5357] recommends padding
truncation to achieve symmetrical sizes (to compensate for the
Session-Reflector's larger test packet header), it's not guaranteed
that the Session-Reflector will truncate the padding, and it's not
possible if there's insufficient padding.
This memo is an update to the TWAMP core protocol specified in This memo is an update to the TWAMP core protocol specified in
[RFC5357]. Measurement systems are not required to implement the [RFC5357]. Measurement systems are not required to implement the
features described in this memo to claim compliance with [RFC5357]. features described in this memo to claim compliance with [RFC5357].
Throughout this memo, the bits marked MBZ (Must Be Zero) MUST be set Throughout this memo, the bits marked MBZ (Must Be Zero) MUST be set
to zero by senders and MUST be ignored by receivers. Also, the HMAC to zero by senders and MUST be ignored by receivers. Also, the HMAC
(Hashed Message Authentication Code) MUST be calculated as defined in (Hashed Message Authentication Code) MUST be calculated as defined in
Section 3.2 of [RFC4656]. Section 3.2 of [RFC4656].
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| Octets to be reflected | Length of padding to reflect | | Octets to be reflected | Length of padding to reflect |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 octets) | | MBZ (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| HMAC (16 octets) | | HMAC (16 octets) |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Padding Length" Field *continues* to specify the number of It is important to note that the "Padding Length" Field continues to
padding octets that the Session-Sender will append to ALL TWAMP-Test specify the number of padding octets that the Session-Sender will
packets associated with this test session. See below for append to ALL TWAMP-Test packets associated with this test session.
considerations on the minimum length of the padding octets, following See below for considerations on the minimum length of the padding
the definitions of the two new fields that follow the Type-P octets, following the definitions of the two new fields that follow
Descriptor. the Type-P Descriptor.
Note that the number of padding octets appended to the Session- Note that the number of padding octets appended to the Session-
Reflector's test packet depends on support for the RECOMMENDED Reflector's test packet depends on support for the RECOMMENDED
truncation process in TWAMP section 4.2.1 [RFC5357]. truncation process in TWAMP section 4.2.1 [RFC5357].
The "Octets to be reflected" Field SHALL be 2 octets long, as shown 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 and contains the octets that the Server MUST reflect in the Accept
Session message as specified below. Session message as specified below.
The "Length of padding to reflect" Field SHALL be 2 octets long, and The "Length of padding to reflect" Field SHALL be 2 octets long, and
contain an unsigned binary value in units of octets. This field contain an unsigned binary value in units of octets. This field
communicates the length of the padding in the TWAMP-Test Packet that communicates the length of the padding in the TWAMP-Test Packet that
the Session-Sender expects to be reflected, and the length of octets the Session-Sender expects to be reflected, and the length of octets
that the Session-Reflector SHALL return in include in its TWAMP-Test that the Session-Reflector SHALL return in its TWAMP-Test packet
packet format (see section 4.2). By including this length field in format (see section 4.2). By including this length field in the
the Request-TW-Session message, a Server is able to determine if it Request-TW-Session message, a Server is able to determine if it can
can comply with a specific request to reflect padding in the TWAMP- comply with a specific request to reflect padding in the TWAMP-Test
Test packets, and to arrange for the Session-Reflector processing in packets, and to arrange for the Session-Reflector processing in
advance. advance.
The "Padding Length" SHOULD be >= 27 octets when specifying a test The "Padding Length" SHOULD be >= 27 octets when specifying a test
session using the Unauthenticated TWAMP-Test mode, to allow for the session using the Unauthenticated TWAMP-Test mode, to allow for the
RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357].
The "Padding Length" SHOULD be >= 56 octets when specifying a test The "Padding Length" SHOULD be >= 56 octets when specifying a test
session using the Authenticated or Encrypted TWAMP-Test modes, to session using the Authenticated or Encrypted TWAMP-Test modes, to
allow for the RECOMMENDED truncation process in TWAMP section 4.2.1 allow for the RECOMMENDED truncation process in TWAMP section 4.2.1
[RFC5357]. [RFC5357].
The "Padding Length" SHALL be > the "Length of padding to reflect" The "Padding Length" SHALL be > the "Length of padding to reflect"
when specifying a test session using the OPTIONAL Reflect Octets when specifying a test session using the OPTIONAL Reflect Octets
mode. mode.
In Unauthenticated TWAMP-Test mode, the "Padding Length" SHALL be >= In Unauthenticated TWAMP-Test mode, the "Padding Length" SHALL be >=
27 + "Length of padding to reflect" octets when specifying a test 27 + "Length of padding to reflect" octets when specifying a test
session using BOTH the OPTIONAL Reflect Octets mode and the session using both the OPTIONAL Reflect Octets mode and the
RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357]. RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357].
In Authenticated or Encrypted TWAMP-Test modes, the "Padding Length" In Authenticated or Encrypted TWAMP-Test modes, the "Padding Length"
SHALL be >= 56 + "Length of padding to reflect" octets when SHALL be >= 56 + "Length of padding to reflect" octets when
specifying a test session using BOTH the OPTIONAL Reflect Octets mode specifying a test session using both the OPTIONAL Reflect Octets mode
and the RECOMMENDED truncation process in TWAMP section 4.2.1 and the RECOMMENDED truncation process in TWAMP section 4.2.1
[RFC5357]. [RFC5357].
3.3. Reflect Octets: Accept Session Packet Format 3.3. Reflect Octets: Accept Session Packet Format
The bits designated for the Reflect Padding feature in the Accept The bits designated for the Reflect Padding feature in the Accept
Session command are as shown in the packet format below. Session command are as shown in the packet format below.
0 1 2 3 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 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
skipping to change at page 9, line 9 skipping to change at page 9, line 50
o When a Server intends octets to be returned in TWAMP-Test packets, o When a Server intends octets to be returned in TWAMP-Test packets,
it MUST send a non-zero value in the Server octets field, and the it MUST send a non-zero value in the Server octets field, and the
TWAMP-Test Sender MUST include those octets at the beginning of TWAMP-Test Sender MUST include those octets at the beginning of
the "Packet Padding (to be reflected)" field the "Packet Padding (to be reflected)" field
o Section 4.1.2 defines how Server octets MUST be included in the o Section 4.1.2 defines how Server octets MUST be included in the
TWAMP-Test packet padding when this service is desired by the TWAMP-Test packet padding when this service is desired by the
Server (indicated in the second of two figures in the section) Server (indicated in the second of two figures in the section)
When supporting the RECOMMENDED truncation process in TWAMP section When performing the truncation process that TWAMP section 4.2.1
4.2.1 [RFC5357], IF calculations on the Padding lengths reveal that [RFC5357] recommends, if calculations on the Padding lengths reveal
there are insufficient octets supplied to produce equal-length that there are insufficient octets supplied to produce equal-length
Session-Sender and Session-Reflector test packets, then the Accept Session-Sender and Session-Reflector test packets, then the Accept
Field MUST be set to 3 = some aspect of the request is not supported. Field MUST be set to 3 to indicate that some aspect of the request is
not supported.
3.4. Additional considerations 3.4. Additional considerations
The value of the Modes Field sent by the Server in the Server 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 Greeting message is the bit-wise OR of the mode values that it is
willing to support during this session. willing to support during this session.
With the publication of this memo as an RFC, the last 7 bit positions 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 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 this extension of [RFC5357] MAY ignore the values in the higher bits
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The Send Schedule is not utilized in TWAMP, and this is unchanged in The Send Schedule is not utilized in TWAMP, and this is unchanged in
this memo. this memo.
4.1.2. Reflect Octets: Packet Formats and Contents 4.1.2. Reflect Octets: Packet Formats and Contents
The Session-Sender packet format and content follow the same The Session-Sender packet format and content follow the same
procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as
indicated in section 4.1.2 of TWAMP [RFC5357]). indicated in section 4.1.2 of TWAMP [RFC5357]).
The Reflect octets mode re-designates the original TWAMP-Test (and The Reflect octets mode re-designates the original TWAMP-Test Packet
OWAMP-Test) Packet Padding Field (see section 4.1.2 of [RFC4656]), as Padding Field (see section 4.1.2 of [RFC4656]), as shown below for
shown below for unauthenticated mode: unauthenticated mode:
0 1 2 3 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 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 | | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp | | Timestamp |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | | | Error Estimate | |
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MUST send a non-zero value in the Server octets field, and the TWAMP- MUST send a non-zero value in the Server octets field, and the TWAMP-
Test Session-Sender MUST include those octets in the first 2 octets Test Session-Sender MUST include those octets in the first 2 octets
of the "Packet Padding (to be reflected)" Field as shown below: of the "Packet Padding (to be reflected)" Field as shown below:
0 1 2 3 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 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 | | Server octets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Packet Padding (to be reflected) | | Remaining Packet Padding (to be reflected) |
. (length in octets specified elsewhere) . . (total length in octets specified in command) .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The "Server octets" field contains the same information that the The "Server octets" field contains the same information that the
Server returned to the Control-Client in the Accept-Session message Server returned to the Control-Client in the Accept-Session message
corresponding to this specific test session (see section 3.3). At corresponding to this specific test session (see section 3.3). At
the Session-Reflector, these octets MUST be reflected the same as the the Session-Reflector, these octets MUST be reflected the same as the
rest of the "Packet Padding (to be reflected)" field. rest of the "Packet Padding (to be reflected)" field.
Note that it is permissible for the Session-Sender to insert the same Note that it is permissible for the Session-Sender to insert the same
octets used in the "Octets to be reflected" field of the Request-TW- octets used in the "Octets to be reflected" field of the Request-TW-
Session command elsewhere in the "Packet Padding (to be reflected)" Session command elsewhere in the "Packet Padding (to be reflected)"
field. field.
4.1.3. Reflect Octets: Interaction with Padding Truncation 4.1.3. Reflect Octets: Interaction with Padding Truncation
When the Reflect Octets mode is selected, and the RECOMMENDED When the Reflect Octets mode is selected, and the performing
truncation process in TWAMP section 4.2.1 [RFC5357] is supported, the truncation process that TWAMP section 4.2.1 [RFC5357] recommends, the
Session-Sender MUST anticipate a minimum padding required to achieve Session-Sender MUST anticipate a minimum padding required to achieve
equal size test packets in both directions. The amount of padding equal size test packets in both directions. The amount of padding
needed to achieve symmetrical packet size depends on BOTH the needed to achieve symmetrical packet size depends on both the
security mode (Unauthenticated/Authenticated/Encrypted) and whether security mode (Unauthenticated/Authenticated/Encrypted) and whether
the Reflect Octets mode is selected simultaneously. the Reflect Octets mode is selected simultaneously.
When using the RECOMMENDED truncation process in TWAMP section 4.2.1 When using the truncation process in TWAMP section 4.2.1 [RFC5357]
[RFC5357] alone, the Session-Sender MUST append sufficient Packet alone, the Session-Sender MUST append sufficient Packet Padding
Padding octets to allow the same IP packet payload lengths to be used octets to allow the same IP packet payload lengths to be used in each
in each direction of transmission (this is usually desirable). To direction of transmission (this is usually desirable). To compensate
compensate for the Session-Reflector's larger test packet format, the for the Session-Reflector's larger test packet format, the Session-
Session-Sender MUST append at least 27 octets of padding in Sender MUST append at least 27 octets of padding in Unauthenticated
Unauthenticated mode, and at least 56 octets in Authenticated and mode, and at least 56 octets in Authenticated and Encrypted modes.
Encrypted modes. The sizes of TWAMP Test protocol packets and the The sizes of TWAMP Test protocol packets and the resulting truncated
resulting truncated padding to achieve equal packet sizes in both padding to achieve equal packet sizes in both directions are shown in
directions are shown in the table below: the table below:
+-------------------+----------------------+---------------------+ +-------------------+----------------------+---------------------+
| Octets in: | Unauthenticated Mode | Auth/Encrypted Mode | | Octets in: | Unauthenticated Mode | Auth/Encrypted Mode |
+-------------------+----------------------+---------------------+ +-------------------+----------------------+---------------------+
| Reflector Header | 41 | 104 | | Reflector Header | 41 | 104 |
| Sender Header | 14 | 48 | | Sender Header | 14 | 48 |
| Truncated Padding | 27 | 56 | | Truncated Padding | 27 | 56 |
+-------------------+----------------------+---------------------+ +-------------------+----------------------+---------------------+
TWAMP-Test Padding Truncation TWAMP-Test Padding Truncation
When using the Reflect Octets mode simultaneously with the When using the Reflect Octets mode simultaneously with the truncation
RECOMMENDED truncation process in TWAMP section 4.2.1 [RFC5357], the process that TWAMP recommends in section 4.2.1 [RFC5357], the
Session-Sender MUST append at least 27 octets of padding plus the Session-Sender MUST append at least 27 octets of padding plus the
"Length of the padding to reflect" octets when operating in "Length of the padding to reflect" octets when operating in
Unauthenticated mode. The Session-Sender MUST append at least 56 Unauthenticated mode. The Session-Sender MUST append at least 56
octets of padding plus the "Length of the padding to reflect" octets octets of padding plus the "Length of the padding to reflect" octets
when operating in Authenticated and Encrypted modes. when operating in Authenticated and Encrypted modes.
4.1.4. Symmetrical Size: Session-Sender Packet Format 4.1.4. Symmetrical Size: Session-Sender Packet Format
When the Symmetrical Size mode is selected, the Session-Sender SHALL When the Symmetrical Size mode is selected, the Session-Sender SHALL
use the following TWAMP-Test Packet Format in Unauthenticated mode: use the following TWAMP-Test Packet Format in Unauthenticated mode:
skipping to change at page 13, line 36 skipping to change at page 14, line 36
. Packet Padding . . Packet Padding .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This feature REQUIRES only a new Session-Sender test packet format, This feature REQUIRES only a new Session-Sender test packet format,
the Session-Reflector test packet format is unchanged. the Session-Reflector test packet format is unchanged.
4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet 4.1.5. Symmetrical Size AND Reflect Octets: Session-Sender Packet
Format Format
When BOTH the Symmetrical Size mode and the Reflect Octets mode are When both the Symmetrical Size mode and the Reflect Octets mode are
selected, the Session-Sender SHALL use the following TWAMP-Test selected, the Session-Sender SHALL use the following TWAMP-Test
Packet Format in Unauthenticated mode: Packet Format in Unauthenticated mode:
Unauthenticated Mode Unauthenticated Mode
0 1 2 3 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 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 | | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp | | Timestamp |
skipping to change at page 15, line 52 skipping to change at page 16, line 52
The "Packet Padding (from Session-Sender)" field MUST be the same The "Packet Padding (from Session-Sender)" field MUST be the same
octets as the "Packet Padding (to be reflected)" field in the octets as the "Packet Padding (to be reflected)" field in the
Session-Sender's test packet, and therefore MUST conform to the Session-Sender's test packet, and therefore MUST conform to the
length specified in the Request-TW-Session message. length specified in the Request-TW-Session message.
When the Server has returned a non-zero value in the "Server octets" When the Server has returned a non-zero value in the "Server octets"
field of the Accept Session message (as described in section 3.3), field of the Accept Session message (as described in section 3.3),
then the Session-Reflector SHALL reflect these octets the same as the then the Session-Reflector SHALL reflect these octets the same as the
rest of the "Packet Padding (to be reflected)" Field. rest of the "Packet Padding (to be reflected)" Field.
When simultaneously using the RECOMMENDED truncation process in TWAMP Section 4.2.1 of [RFC5357] recommends a padding truncation process
section 4.2.1 [RFC5357] AND Reflect octets mode, the Session- for use in TWAMP. When using that process in conjunction with the
Reflector MUST reflect the designated octets from the Session- Reflect octets mode, the Session-Reflector MUST reflect the
Sender's test packet in the "Packet Padding (from Session-Sender)" designated octets from the Session-Sender's test packet in the
Field, and MAY re-use additional Packet Padding from the Session- "Packet Padding (from Session-Sender)" Field, and MAY re-use
Sender. The Session-Reflector MUST truncate the padding such that additional Packet Padding from the Session-Sender. The Session-
the highest number octets are discarded, and the test packet length Reflector MUST truncate the padding such that the highest number
equals the Session-Sender's packet length. When using the octets are discarded, and the test packet length equals the Session-
RECOMMENDED truncation process, the Session-Reflector MUST truncate Sender's packet length. When using the recommended truncation
exactly 27 octets of padding in Unauthenticated mode, and exactly 56 process, the Session-Reflector MUST truncate exactly 27 octets of
octets in Authenticated and Encrypted modes. 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 In any case, the Session-Reflector MAY re-use the Sender's Packet
the requirements for padding generation are the same for each). Padding (since the requirements for padding generation are the same
for each).
4.2.2. Symmetrical Size: Session-Reflector Packet Format 4.2.2. Symmetrical Size: Session-Reflector Packet Format
When Symmetrical Size mode is selected, the Session-Sender packet When Symmetrical Size mode is selected, the Session-Reflector packet
formats for unauthenticated and authenticated/encrypted modes are formats for unauthenticated and authenticated/encrypted modes are
identical to the core TWAMP specification, section 4.2.1 of identical to the core TWAMP specification, section 4.2.1 of
[RFC5357]. Thus, the Session-Reflector test packet format is [RFC5357]. Thus, the Session-Reflector test packet format is
unchanged. unchanged.
The Session-Reflector MUST construct its test packet using the The Session-Reflector MUST construct its test packet using the
information in the Session-Sender's test packet. The length of 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-Reflector's test packet SHALL equal the length of the
Session-Sender's test packet. Session-Sender's test packet.
4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet 4.2.3. Symmetrical Size AND Reflect Octets: Session-Sender Packet
Format Format
When BOTH the Symmetrical Size mode and the Reflect Octets mode are When both the Symmetrical Size mode and the Reflect Octets mode are
selected, the Session-Reflector MUST operate using the selected, the Session-Reflector MUST operate using the Session-
Session_Reflector Packet Format defined in section 4.1.5, where the Reflector Packet Format defined in section 4.1.5, where the Padding
Padding Octets are separated from the information fields, and the Octets are separated from the information fields, and the Padding to
Padding to be Reflected field precedes the Additional Padding. be Reflected field precedes the Additional Padding.
The Session-Reflector SHALL use the same TWAMP-Test Packet Format as The Session-Reflector SHALL use the same TWAMP-Test Packet Format as
specified in section 4.2.1 above. specified in section 4.2.1 above.
5. Security Considerations 5. Security Considerations
These extended modes of operation do not appear to permit any new These extended modes of operation do not appear to permit any new
attacks on hosts communicating with core TWAMP [RFC5357]. attacks on hosts communicating with core TWAMP [RFC5357].
The security considerations that apply to any active measurement of The security considerations that apply to any active measurement of
skipping to change at page 17, line 30 skipping to change at page 18, line 32
registry values that correspond to single bit positions, unless there registry values that correspond to single bit positions, unless there
is a good reason to do otherwise (more complex encoding than single is a good reason to do otherwise (more complex encoding than single
bit positions may be used in the future, to access the 2^32 value bit positions may be used in the future, to access the 2^32 value
space). space).
6.2. Registry Contents 6.2. Registry Contents
TWAMP Modes Registry is recommended to be augmented as follows: TWAMP Modes Registry is recommended to be augmented as follows:
Value Description Semantics Definition 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
16 Individual Session RFC????, Section 3.1
Control bit position (4)
-------------------------------------------------------- --------------------------------------------------------
xxx Reflect Octets this memo, section 3.1 xxx Reflect Octets this memo, section 3.1
Capability new bit position (X) Capability new bit position (X)
yyy Symmetrical Size this memo, section 3.1 yyy Symmetrical Size this memo, section 3.1
Sender Test Packet Format new bit position (Y) Sender Test Packet Format new bit position (Y)
>>>IANA: change xxx, yyy, X, Y, and RFC???? to the assigned values >>>IANA: change xxx, yyy, X, Y, and RFC???? to the assigned values
The suggested values are The suggested values are
X=5, xxx=32 X=5, xxx=32
Y=6, yyy=64 <<<< Y=6, yyy=64 <<<<
7. Acknowledgements 7. Acknowledgements
The authors thank Steve Baillargeon, Walt Steverson, and Stina Ross The authors thank Steve Baillargeon, Walt Steverson, and Stina Ross
for helpful review and comments. for helpful review and comments.
8. References 8. References
skipping to change at page 18, line 24 skipping to change at page 19, line 17
8.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006. (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. [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008. RFC 5357, October 2008.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the [RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
August 2009. August 2009.
8.2. Informative References 8.2. Informative References
Authors' Addresses Authors' Addresses
Al Morton Al Morton
AT&T Labs AT&T Labs
200 Laurel Avenue South 200 Laurel Avenue South
Middletown,, NJ 07748 Middletown,, NJ 07748
USA USA
Phone: +1 732 420 1571 Phone: +1 732 420 1571
Fax: +1 732 368 1192 Fax: +1 732 368 1192
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