Network Working Group S. Baillargeon INTERNET-DRAFT C. Flinta Intended Status: Standards Track A. Johnsson Expires: July 16, 2011 S. Ekelin Ericsson January 12, 2011 TWAMP Value-Added Octets draft-baillargeon-ippm-twamp-value-added-octets-00.txt Abstract This memo describes the optional extensions to the standard TWAMP test protocol for identifying test sessions and packet trains, and for measuring the one-way IP-layer available path capacity, IP-layer tight link capacity and UDP throughput in the forward and reverse path directions. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2011 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 Baillargeon, et al. Expires July 16, 2011 [Page 1] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Baillargeon, et al. Expires July 16, 2011 [Page 2] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Requirements Language . . . . . . . . . . . . . . . . . . . 5 2 Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . 5 3 Measurement Principles for Capacity and Throughput Metrics . . . 5 4 Principles for Test packet Demultiplexing . . . . . . . . . . . 7 5 TWAMP Control Considerations . . . . . . . . . . . . . . . . . . 8 5.1 Padding Length . . . . . . . . . . . . . . . . . . . . . . 8 5.2 Length of padding to reflect . . . . . . . . . . . . . . 10 5.3 Additional Considerations . . . . . . . . . . . . . . . . 11 6 Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . 11 6.1 Sender Behavior . . . . . . . . . . . . . . . . . . . . . 11 6.1.1 Packet Timings . . . . . . . . . . . . . . . . . . . 12 6.1.2 Session-Sender Packet Format and Content . . . . . . 12 6.2 Reflector behavior . . . . . . . . . . . . . . . . . . . 19 6.2.1 Session-Reflector Packet Format and Content . . . . 21 6.3 Additional Considerations . . . . . . . . . . . . . . . . 21 7 Security Considerations . . . . . . . . . . . . . . . . . . . 22 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.1 Normative References . . . . . . . . . . . . . . . . . . 22 9.2 Informative References . . . . . . . . . . . . . . . . . 23 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Baillargeon, et al. Expires July 16, 2011 [Page 3] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 1 Introduction The notion of embedding a number of meaningful fields in the padding octets has been established as a viable methodology for carrying additional information within the TWAMP-Test protocol running between a Session-Sender and a Session-Reflector [RFC5357] [RFC6038]. This memo defines an OPTIONAL set of value-added octets of information that are placed at the beginning of the Packet Padding field [RFC5357] or at the beginning of the Packet Padding (to be reflected) field [RFC6038] by the Session-Sender, and are reflected or returned by the Session-Reflector. The length of value-added octets varies in size between 6, 10 and 14 octets depending on the setting of the flag bits specified at the beginning of the value- added octets. The value-added octets MAY be used for demultiplexing packets to the correct test session, identifying packets belonging to a train of a test session and/or measuring the IP-layer available path capacity (APC), IP-layer tight link capacity (TLC) and UDP throughput on both the forward and reverse paths. This memo also defines the OPTIONAL behaviors of the Session-Sender and Session-Reflector to enable the demultiplexing of test packets to the correct test session and to enable the measurements of the IP- layer APC, IP-layer TLC and UDP throughput on both forward and reverse paths based on information provided in the TWAMP test packets including the value-added octets. UDP throughput is defined in the Benchmarking Terminology for Network Interconnection Devices specification [RFC1242]. IP-Type-P APC and TLC are defined in the Defining Network Capacity specification [RFC5136] and Amendment 1 of the Quality of Service and Network Performance specification [Y1540A1]. The actual method to calculate the available path capacity, the tight link capacity or the UDP throughput from packet-level data performance data is not discussed in this memo. The value-added padding octets MAY be used with any TWAMP modes including TWAMP Light [RFC5357]. This memo does not introduce any changes to the TWAMP-Control protocol. Measurement systems are not required to implement the value-added octets and related behaviors described in this memo to claim compliance with TWAMP [RFC5357]. Baillargeon, et al. Expires July 16, 2011 [Page 4] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 1.1 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]. 2 Purpose and scope The purpose of this memo is as follows: o Define a structure for embedding a sequence of value-added fields at the beginning of the Packet Padding field [RFC5037] or Packet Padding (to be reflected) field [RFC6038] in the TWAMP test packets and, o Define the Session-Sender and Session-Reflector behaviors to enable the demultiplexing of test packets to the correct test session and measurements of IP-layer APC, IP-layer TLC and UDP throughput on both the forward and reverse paths The scope of the memo is limited to the specifications of the following functions: o The definition of an OPTIONAL Session-Sender behavior o The definition of an OPTIONAL Session-Reflector behavior The definition of the OPTIONAL Session-Sender behavior includes a description of the value-added fields to communicate version number, flag bits, sender discriminator, sequence number of the last packet in a train and desired inter-packet time interval (or per-packet waiting time) for the reverse path direction of transmission. The OPTIONAL packet padding octets are designed to retain backward compatibility with the original TWAMP test protocol [RFC5357]. 3 Measurement Principles for Capacity and Throughput Metrics Most capacity estimation methods,e.g. [RRBNC][PDM][ENHJMMB][SBW] for available capacity and [RFC2544] for UDP throughput, need to send and receive packets in groups, called packet trains or simply trains. Each train is sent at a specific transmission rate in a given direction. These trains must be identified within each bi-directional Baillargeon, et al. Expires July 16, 2011 [Page 5] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 test session stream. The first measurement principle is to send multiple trains within a test session stream from one IP node to another IP node in order to estimate the IP-layer available path capacity, IP-layer tight link capacity or UDP throughput in the forward direction. Each train consists of a group of test packets which are separated from each other by a packet interval, as shown in the picture below. tt tt tt |<---------->| |<---------->| |<---------->| | | | | | | +------------+ +------------+ +------------+ | Packet 1 | | Packet 2 | | Packet 3 | +------------+ +------------+ +------------+ | | | |<--------------------->|<--------------------->| packet interval 1 packet interval 2 The packet interval between consecutive packets for each train sent by the Session-Sender and reflected by the Session-Reflector MUST be calculated and determined by the controller or an application or entity communicating with the controller. The packet interval MAY be constant within a train. Determination of the packet interval within a train as well as for consecutive trains for a given test session is implementation-specific. The transmission time tt to send one packet (i.e. determined by the interface speed and the IP packet size) is also shown in the picture. Observe that the packet interval MUST be larger than or equal to tt. At the Session-Reflector, each received test packet within a forward train is time stamped. This provides a second set of packet interval values. Methods for measuring IP-layer available path capacity, IP- layer tight link capacity and UDP throughput use the packet intervals obtained from both end points in the estimation process. The method to measuring the UDP throughput may also require the packet loss at the receiving end. The estimation process itself as well as any requirements on software or hardware is implementation-specific. The second measurement principle is referred to as self-induced congestion. According to this principle, in order to measure the available path capacity, tight link capacity and UDP throughput, some trains MUST cause momentary congestion on the network path. In Baillargeon, et al. Expires July 16, 2011 [Page 6] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 essence this means that some trains MUST be sent at a higher rate than what is available on the network path. The congestion is only transient, for the duration of the train which is typically short. In order to fulfill the above measurement principles and to measure the IP-layer available path capacity, IP-layer tight link capacity and UDP throughput in the reverse direction, the reflected test packets MUST be re-grouped into trains at the Session-Reflector. 4 Principles for Test packet Demultiplexing The controller (or the Session-Sender) requires a method for demultiplexing the received test packets to the correct test session especially when it manages multiple active test sessions. The responder also requires a method for demultiplexing the received test packets from multiple active test sessions originating from the same controller or from different controllers. The purpose of this section is to provide some basic principles for identifying the test packets and to clarify the optional usage of the Sender Discriminator (SD) field described in this memo. It is important to note the actual method for identifying a test packet and the process for mapping it to the correct test session are implementation-specific. They may differ between various controllers and responders. In general, the methods are based on fields available in the various headers of the TWAMP test packet (e.g. Ethernet, IP, UDP and TWAMP headers). Note the SID [RFC4656] is generally not used for identification purpose since it does not normally appear in the TWAMP test packets. As an example, a management system (controller or responder) may use the source IP address of the incoming test packet in order to associate it to the correct test session. This method is valid but has a number of limitations. It is simple and effective when each measurement system only requires a single test session for each peer but fails when multiple test sessions (with different characteristics) are running between the same pair of controller and responder. Another approach is to use a combination of the source IP address and source (or destination) UDP port. This method is also valid but to work effectively, it requires that the controller allocates multiple UDP ports (one for each test session for instance) and/or the responder listens on multiple ports. Ideally, a measurement system should limit the number of UDP ports for sending and receiving test packets. This approach may be improved by using a combination of the source IP address, source UDP port and DSCP codepoint. This method also has its limitations. For instance, it cannot identify test Baillargeon, et al. Expires July 16, 2011 [Page 7] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 packets from different test sessions running between the same pair of controller and responder if they are using the same UDP endpoints and the same DSCP codepoint. This memo introduces a new field, the Sender Discriminator (SD) field intended to simplify the identification of the test packets at the controller and responder. It is especially useful when multiple test sessions are expected to be running between the same pair of controller and responder. As described in 6.1.2, the SD is a number generated by the Session-Sender that uniquely identifies a test session on its system. With this field, the controller may explicitly identify the test packets belonging to a test session. The responder may also use the SD field in combination of the source IP address for instance to identify the test packets belonging to a test session. 5 TWAMP Control Considerations This memo does not introduce any changes to the TWAMP-Control protocol. The value-added padding octets are intended to work with any TWAMP modes including TWAMP Light test sessions [RFC5357] running without the TWAMP-control protocol. Both the Reflect Octets mode and Symmetrical Size mode SHOULD be selected to ensure the reflection of the value-added padding octets by the Session-Reflector and symmetrical size TWAMP-Test packets in the forward and reverse directions of transmission. The forward and reverse APC, TLC and UDP throughput measurement characteristics depend on the size of the test packets. All test packets (forward and reverse test packets) belonging to a specific test session responsible to measure the available path capacity, tight link capacity and/or UDP throughput MUST have the same IP packet size. 5.1 Padding Length The length of the value-added octets is as follows: o 6 octets when the Session-Sender supports the packet to session identification process based on a discriminator value (S flag bit is set 1, L flag bit set to 0 and D flag bit is set to 0, o 6 octets when the Session-Sender supports the packet train identification process based on a sequence number (S flag bit is set to 0, L flag bit set to 1 and D flag bit is set to 0), o 10 octets when the Session-Sender supports the packet to Baillargeon, et al. Expires July 16, 2011 [Page 8] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 session identification process and the packet train identification process (S flag bit is set to 1, L flag bit set to 1 and D flag bit is set to 0), o 10 octets when the Session-Sender supports the packet train identification process and the APC measurements (S flag bit is set to 0, L flag bit set to 1 and D flag bit is set to 1), o 14 octets when the Session-Sender supports the packet to session identification process, the packet train identification process and the APC/TLC measurements (S, D and L flag bits are set to 1). The value of the Padding Length field in the Request-TW-Session command is specified as follows: o The Padding Length MUST be >= 33, 37 or 41 octets when specifying a test session using the Unauthenticated TWAMP-Test mode, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends. o The Padding Length MUST be >= 33, 37 or 41 octets when specifying a test session using the Unauthenticated TWAMP-Test mode in conjunction with the Reflect Octets mode with a zero value in the Server octets field, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends. o The Padding Length MUST be >= 35, 49 or 43 octets when specifying a test session using the Unauthenticated TWAMP-Test mode in conjunction with the Reflect Octets mode with a non- zero value in the Server octets field, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends o The "Padding Length" MUST be >= 6, 10 or 14 octets when specifying a test session using the Unauthenticated TWAMP-Test mode in conjunction with the Symmetrical Size mode. o The Padding Length MUST be >= 6, 10 or 14 octets when specifying a test session using the Unauthenticated TWAMP-Test mode in conjunction with the Symmetrical Size mode and Reflect Octets mode with a zero value in the Server octets field. o The Padding Length MUST be >= 8, 12 or 16 octets when specifying a test session using the Unauthenticated TWAMP-Test mode in conjunction with the Symmetrical Size mode and Reflect Octets mode with a non-zero value in the Server octets field. Baillargeon, et al. Expires July 16, 2011 [Page 9] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 o The "Padding Length" MUST be >= 62, 66, 70 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends. o The "Padding Length" MUST be >= 62, 66, 70 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes in conjunction with the Reflect Octets mode with a zero value in the Server octets field, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends. o The "Padding Length" MUST be >= 64, 68, 72 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes in conjunction with the Reflect Octets mode with a non-zero value in the Server octets field, to allow for the truncation process that TWAMP section 4.2.1 [RFC5357] recommends. o The Padding Length MUST be >= 6, 10 or 14 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes in conjunction with the Symmetrical Size mode. o The Padding Length MUST be >= 6, 10 or 14 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes in conjunction with the Symmetrical Size mode and Reflect Octets mode with a zero value in the Server octets field. o The Padding Length MUST be >= 8, 12 or 16 octets when specifying a test session using the Authenticated or Encrypted TWAMP-Test modes in conjunction with the Symmetrical Size mode and Reflect Octets mode with a non-zero value in the Server octets field. 5.2 Length of padding to reflect The section is only applicable for the Reflect Octets mode. The value of the Length of padding to reflect field in the Request- TW-Session command is specified as follows: o The Length of padding to reflect MUST be >= 6, 10 or 14 octets when specifying a test session using the Reflect Octets mode with a zero value in the Server octets field. o The Length of padding to reflect MUST be >= 8, 12 or 16 octets Baillargeon, et al. Expires July 16, 2011 [Page 10] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 when specifying a test session using the Reflect Octets mode with a non-zero value in the Server octets field. 5.3 Additional Considerations The desired behavior at the Session-Reflector MAY be negotiated via the TWAMP-Control protocol in the future. This is outside the scope of this specification. 6 Extended TWAMP Test The TWAMP-test protocol carrying the value-added padding octets is identical to TWAMP [RFC5357] except for the definition of first 6, 10 or 14 octets in the Padding Octet field that the Session-Sender expects to be reflected. The Session-Sender and Session-Reflector behaviors are also modified. 6.1 Sender Behavior This section describes the extensions to the behavior of the TWAMP Session-Sender. When a test session is configured for demultiplexing test packets to a test session based on a discriminator value, the Session-Sender MUST set the Sender Discriminator Present bit to 1 and MUST generate and transmit a unique nonzero discriminator value in the Sender Discriminator field. When a test session is configured for tagging the packets belonging a train of a test session based on a sequence number corresponding, the Session-Sender MUST set the Last Seqno in Train Present bit to 1 and MUST generate and transmit a valid sequence number in the Last Seqno in Train field. When a test session is configured for APC/TLC or UDP throughput measurements (including the packet train identification process), the Session-Sender MUST set the Last Seqno in Train Present bit to 1 and the Desired Reverse Packet Interval Present bit to 1, and MUST generate and transmit the appropriate values in the Last Seqno in Train and Desired Reverse Packet Interval fields. The Session-Sender MUST also group the test packets in trains and send the trains towards the Session-Reflector at the desired forward packet intervals provided by the available path capacity or throughput measurement method, tool or algorithm. The setting of Desired Reverse Rate Interval parameters is implementation specific for a given available path capacity or throughput measurement method. It is outside the Baillargeon, et al. Expires July 16, 2011 [Page 11] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 scope of this specification. The Session-Sender MUST not use any of the value-added padding octets when a test session is not configured for tagging the test packets with a discriminator value or last sequence number in a train, or when the test session is not configured for APC/TLC or UDP throughput measurements. 6.1.1 Packet Timings The Send Schedule is not utilized in TWAMP and this is unchanged in this memo. 6.1.2 Session-Sender Packet Format and Content The Session-Sender packet format and content follow the same procedure and guidelines as defined in TWAMP [RFC5357] and TWAMP Reflect Octets and Symmetrical Size Features [RFC6038]. This feature allows the Session-Sender to set the first few octets in the TWAMP-Test Packet Padding field with information that are considered useful for identifying test packets belonging to a test session or packet train, or with information deemed necessary for calculating the one-way APC, one-way TLC and/or one-way UDP throughput in each direction of transmission. A version number and a sequence of flag bits are defined at the very beginning of the value-added padding octets. The version number identifies the version of the value-added padding octets and meaning of the flag bits. Each flag bit indicates if a specific field of a specific size is present in the valued-added padding octets. The flag bits are designed to accommodate different combinations of fields while reducing padding overhead when certain fields are not needed. The version number and flag bits also provide an effective method for parsing information at Session-Reflector and Session-Sender. This document defines version 1 with three flag bits: S, L and D. In the future, other flag bits may be defined to allow additional padding fields. This is outside the scope of this specification. The format of the test packet depends on the TWAMP mode and flag bits being used. Baillargeon, et al. Expires July 16, 2011 [Page 12] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 For unauthenticated mode with the S flag bit set to 1, the L flag bit set to 0 and D flag bit set to 0: 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 | Ver |S|L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ For unauthenticated mode with the S flag bit set to 0, the L flag bit set to 1 and D flag bit set to 0: 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 | Ver |S|L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Seqno in Train | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Baillargeon, et al. Expires July 16, 2011 [Page 13] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 For unauthenticated mode with the S flag bit set to 1, the L flag bit set to 1 and D flag bit set to 0: 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 | Ver |S|L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Seqno in Train | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ For unauthenticated mode with the S flag bit set to 0, the L flag bit set to 1 and D flag bit set to 1: 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 | Ver |S|L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Seqno In Train | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Desired Reverse Packet Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Baillargeon, et al. Expires July 16, 2011 [Page 14] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 For unauthenticated mode with the S flag bit set to 1, the L flag bit set to 1 and D flag bit set to 1: 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 | Ver |S|L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Seqno In Train | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Desired Reverse Packet Interval | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Baillargeon, et al. Expires July 16, 2011 [Page 15] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 For the unauthenticated mode, Symmetrical Size mode and Reflect Octets mode with a zero value in the Server octets field plus the S, L and D flag bits set to 1:. 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) | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Ver |S|L|D| Reserved | Sender... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Discriminator | Last... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Seqno in Train | Desired... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reverse Packet Interval | Additional... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Packet Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Baillargeon, et al. Expires July 16, 2011 [Page 16] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 For the unauthenticated mode, Symmetrical Size mode and Reflect Octets mode with a non-zero value in the Server octets field plus the S, L and D flag bits set to 1:. 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) | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Server octets | Ver |S|L|D| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Sender Discriminator... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Last Seqno... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | In Train | Desired Reverse Packet... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interval | Additional Packet... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Padding | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ In the combined mode including Reflect Octets, the value-added padding octets are embedded in the Packet Padding (to be reflected) field. The Version field MUST be encoded in the first 4 bits. It identifies Baillargeon, et al. Expires July 16, 2011 [Page 17] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 the version number of the value-added padding octets and meaning of the flag bits. This document defines version 1. The Sender Discriminator Present bit (S) MUST be the first flag. If the Sender Discriminator Present bit is set to 1, then a Sender Discriminator field MUST be present and MUST contain valid information. The Last Seqno in Train Present bit (L) MUST be the second flag. If the Last Seqno in Train Present bit is set to 1, then the Last Seqno in Train field MUST be present and MUST contain valid information. The Desired Reverse Packet Interval Present bit (D) MUST be the third flag. If the Desired Reverse Packet Interval Present bit is set to 1, then Desired Reverse Packet Interval Present field MUST be present and MUST contain valid information. The Reserved field is reserved for future use. All 9 bits of the Reserved field MUST be transmitted as zero by the Session-Sender. The Sender Discriminator (SD) field MUST contain an unsigned 32 bit integer generated by the Session-Sender. It is used by the Session- Reflector and/or Session-Sender to identify packets belonging to a test session. The Session-Sender MUST choose a nonzero discriminator value that is unique among all test sessions on its system. This field is present only if the Sender Discriminator Present bit is set to one. The Last Seqno in Train MUST contain an unsigned 32 bit integer generated by the Session-Sender. It MUST indicate the expected sequence number of the last packet in the train. It SHOULD be used by the Session-Sender and Session-reflector to identify the train a test packet belongs to. The packets belonging to a train are determined by observing the test packet sequence number in relation to the Last Seqno for a train. The sequence number of a packet in a train MUST be lower than or equal to the Last Seqno for that train. The sequence number MUST also be larger than the Last Seqno for the previous train. This field is present only if the Last Seqno in Train Present bit is set to one. The Desired Reverse Packet Interval (DRPI) MUST contain an unsigned 32 bit integer generated by the Session-Sender. It MUST indicate the desired inter-packet time interval (or the waiting time) that the Session-Reflector SHOULD use when transmitting the reflected test packets towards the Session-Sender. The format of this field MUST be a fractional part of a second as defined in OWAMP [RFC4656]. This field is present only if the Desired Reverse Packet Interval Present bit is set to one. Baillargeon, et al. Expires July 16, 2011 [Page 18] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 The method by which the Sender Discriminator and Desired Reverse Packet Interval values are obtained is outside of the scope of this document. 6.2 Reflector behavior The TWAMP Session-Reflector follows the procedures and guidelines in Section 4.2 of [RFC5357], with some changes and additional functions. When the Session-Reflector is configured for packet to session identification based on a sender discriminator value: o The Session-Reflector MUST read the Version field and the S flag as test packets are received. o If the Version field and the S flag bit are both equal to 1, the Session-Reflector MUST continue reading and extracting the information from the Sender Discriminator field in the value- added padding octets. o After reading and extracting the information from the Sender Discriminator field, the Session-Reflector MUST associate the test packets to the correct test session based on the value specified in the Sender Discriminator field and the source IP address specified in the IP header of the test packet. The actual method for demultiplexing the received test packets to the correct test session based on the Sender Discriminator and source IP address is outside the scope of this specification. The Session-Reflector MAY also use additional packet fields to demultiplex test packets to a test session. o If the Version field or the S flag bit is not equal to 1, the Session-Reflector SHOULD ignore the Sender Discriminator field and SHOULD follow the procedures and guidelines described in section 4.2 of [RFC5357]. When the Session-Reflector is configured for APC/TLC or UDP throughput measurements (including the packet train identification process): o The Session-Reflector MUST read the Version field, the L flag and the D flag as test packets are received. o If the Version field, the L flag bit and the D flag bit are Baillargeon, et al. Expires July 16, 2011 [Page 19] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 equal to 1, the Session-Reflector MUST continue reading and extracting the information from the Last Seqno in Train and Desired Reverse Packet Interval fields in the value-added padding octets. o After reading and extracting the information from the Last Seqno in Train and Desired Reverse Packet Interval fields, the Session-Reflector MUST buffer the packets belonging to the current train (or store the packet-level performance data). When all packets belonging to the current train have been received, the Session-Reflector SHOULD transmit them in a new train with a waiting time (packet interval) for each packet indicated in the Desired Reverse Packet Interval field. If the Desired Reverse Packet Interval field is set to zero, then the Session-Reflector SHOULD transmit the packet as immediately as possible. The Session-Reflector MUST not reorder the test packets if they happen to arrive out-of-sequence. o For each incoming packet within a train of a test session stream, the Last Seqno in Train MUST be compared to Sequence number in the same packet in order to determine when a complete train has been collected. A train SHOULD be transmitted as immediately as possible after the last packet of the train has been received. The last packet within a train has Sender Sequence Number = Last Seqno in Train. o The Last Seqno in Train of a packet MUST also be compared to the Last Seqno in Train of the previous packet in order to determine if a new train needs to be collected. In case of packet loss, the Session-Reflector MUST transmit the incomplete train when it receives a packet with a Last SeqNo in Train belonging to the another train (e.g. next train) of the test session, or after a timeout. The timeout MAY be the REFWAIT timer specified in section 4.2 of [RFC5357]. o Packets arriving out-of-order within a train MUST be buffered at the Session-Reflector if the train is not yet transmitted to the Session-Sender. If the train is already transmitted, the test packet SHOULD be returned to the Session-Sender as quickly as possible. o If the Version field, the L flag or D flag is not equal to 1, the Session-Reflector SHOULD ignore the Last Seqno in Train and Desired Reverse Packet Interval fields fields, SHOULD follow the procedures and guidelines described in section 4.2 of [RFC5357] and SHOULD transmit the packet as immediately as possible including the test packets that are currently stored for the test session. Baillargeon, et al. Expires July 16, 2011 [Page 20] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 The Session-Reflector MUST implement the changes described above when the Session-Reflector supports the APC/TLC/UDP throughput measurements (including the packet train identification process) and the packet to session identification process. The Session-Reflector MUST ignore the value-added octets and MUST follow the procedures and guidelines described in section 4.2 of [RFC5357] when the Session-Reflector does not support APC/TLC/UDP throughput measurements or the packet to session identification process. 6.2.1 Session-Reflector Packet Format and Content The Session-Reflector packet format and content follow the same procedure and guidelines as defined in TWAMP [RFC5357] and TWAMP Reflect Octets and Symmetrical Size Features [RFC6038], with the following changes: o The Session-Reflector MUST re-use (reflect) the value-added padding octets (6, 10 or 14 octets) provided in the Sender's Packet Padding. o The Session-Reflector MAY re-use the rest of the padding octets in the Sender's Packet Padding. When using the recommended truncation process [RFC5357], the Session- Reflector MUST truncate exactly 27 octets of padding in Unauthenticated mode,and exactly 56 octets in Authenticated and Encrypted modes. 6.3 Additional Considerations It is not required to use the Sender Discriminator field for calculating the one-way APC, one-way TLC and/or one-way UDP throughput. The Sender Discriminator Present bit can be set to zero. However, the Session-Sender and Session-Reflector MUST implement a local policy to identify the test packets belonging to a specific test session. The method for demultiplexing the received test packets to the correct test session based on other packet fields (e.g. fields in the IP header) is outside the scope of this specification. APC/TLC/UDP throughput measurements introduce an additional consideration when the test sessions operate in TWAMP Light. When the Session-Reflector does not have knowledge of the session state, the measurement system will only be capable to estimate or calculate the Baillargeon, et al. Expires July 16, 2011 [Page 21] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 available path capacity, tight link capacity and UDP throughput in the forward path direction of transmission. APC/TLC/UDP Throughput measurements in the reverse path direction requires the Session- Reflector to have knowledge of the session state and be capable to identify the test packets belonging to a specific test session. The method for creating a session state from the initial test packets on the TWAMP Light Session-Reflector is outside the scope of this specification. 7 Security Considerations The value-added octets 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]. 8 IANA Considerations This document has no actions for IANA. 9 References 9.1 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. [RFC1242] Bradner, S., "Benchmarking Terminology for Network Interconnection Devices", RFC 1242, July 1991. [RFC5136] Chimento, P. and Ishac,J., "Defining Network Capacity", RFC 5136, February 2008. [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, October 2008. [RFC6038] Morton, A., Ciavattone, L., TWAMP Reflect Octets and Symmetrical Size Features, RFC6038 , October 2010. Baillargeon, et al. Expires July 16, 2011 [Page 22] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 [RFC2544] Bradner,S., McQuaid, J., "Benchmarking Terminology for Network Interconnect Devices", RFC 2544, March 1999. 9.2 Informative References [RRBNC] Ribeiro, V., Riedi, R., Baraniuk, R., Navratil, J., Cottrel, L., Pathchirp: Efficient available bandwidth estimation for network paths, Passive and Active Measurement Workshop, 2003. [PDM] Dovrolis, C., Ramanathan, P., and Moore D., Packet Dispersion Techniques and a Capacity Estimation Methodology, IEEE/ACM Transactions on Networking, December 2004. [ENHJMMB] Ekelin, S., Nilsson, M., Hartikainen, E., Johnsson, A., Mangs, J., Melander, B., Bjorkman, M., Real-time measurement of end-to-end available bandwidth using kalman filtering, Proceedings to the IEEE IFIP Network Operations and Management Symposium, 2006. [SBW] Sommers, J., Barford, P., Willinger, W., Laboratory-based calibration of available bandwidth estimation tools, Microprocess Microsyst., 2007. [Y1540A1] ITU-T Y.1540 Amendment 1, Appendix VIII, IP Layer Capacity Framework, March 2009. [MRM] Morton, A., Ramachandran, G., Maguluri, G., Reporting Metrics Different Points of View, draft-ietf-ippm- reporting-metrics-03, June 2010. Author's Addresses Steve Baillargeon Ericsson 3500 Carling Avenue Ottawa, Ontario K2H 8E9 Canada EMail: steve.baillargeon@ericsson.com Christofer Flinta Ericsson Farogatan 6 Stockholm, 164 80 Baillargeon, et al. Expires July 16, 2011 [Page 23] INTERNET DRAFT Value-Added TWAMP Octets January 12, 2011 Sweden EMail: christofer.flinta@ericsson.com Andreas Johnsson Ericsson Farogatan 6 Stockholm, 164 80 Sweden EMail: andreas.a.johnsson@ericsson.com Svante Ekelin Ericsson Farogatan 6 Stockholm, 164 80 Sweden EMail: svante.ekelin@ericsson.com Baillargeon, et al. Expires July 16, 2011 [Page 24]