Network Working Group Jerry Perser INTERNET-DRAFT Spirent Expires in: August 2003 David Newman Network Test Sumit Khurana Telcordia Shobha Erramilli QNetworx Scott Poretsky Avici Systems February 2002 Terminology for Benchmarking Network-layer Traffic Control Mechanisms Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Table of Contents 1. Introduction .............................................. 3 2. Existing definitions ...................................... 3 3. Term definitions ............................................4 3.1 Configuration Terms 3.1.1 Classification .........................................4 3.1.2 Codepoint Set ..........................................4 3.1.3 Forwarding Congestion ..................................5 3.1.4 Congestion Management ..................................6 3.1.5 Flow ...................................................6 3.2 Measurement Terms Perser, Newman, Khurana, Erramilli, Poretsky [Page 1] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.2.1 Channel Capacity .......................................7 3.2.2 Conforming .............................................8 3.2.3 Nonconforming ..........................................8 3.2.4 Delay ..................................................9 3.2.5 Jitter ................................................10 3.2.6 Undifferentiated Response .............................11 3.3 Sequence Tracking 3.3.1 In-sequence Packet ....................................11 3.3.2 Out-of-order Packet ...................................12 3.3.3 Duplicate Packet ......................................12 3.3.4 Stream ................................................13 3.3.5 Test Sequence number .................................13 3.4 Vectors ...................................................14 3.4.1 Intended Vector .......................................14 3.4.2 Offered Vector ........................................15 3.4.3 Expected Vectors 3.4.3.1 Expected Forwarding Vector ........................15 3.4.3.2 Expected Loss Vector ..............................16 3.4.3.3 Expected Sequence Vector ..........................16 3.4.3.4 Expected Instantaneous Delay Vector ...............17 3.4.3.5 Expected Average Delay Vector .....................18 3.4.3.6 Expected Maximum Delay Vector .....................18 3.4.3.7 Expected Minimum Delay Vector .....................19 3.4.3.8 Expected Instantaneous Jitter Vector ..............20 3.4.3.9 Expected Average Jitter Vector ....................21 3.4.3.10 Expected Peak-to-peak Jitter Vector ..............21 3.4.4 Output Vectors 3.4.4.1 Forwarding Vector .................................22 3.4.4.2 Loss Vector .......................................22 3.4.4.3 Sequence Vector ...................................23 3.4.4.4 Instantaneous Delay Vector ........................24 3.4.4.5 Average Delay Vector ..............................25 3.4.4.6 Maximum Delay Vector ..............................26 3.4.4.7 Minimum Delay Vector ..............................26 3.4.4.8 Instantaneous Jitter Vector .......................27 3.4.4.9 Average Jitter Vector .............................28 3.4.4.10 Peak-to-peak Jitter Vector .......................29 4. Security Considerations ....................................30 5. Normative References .......................................30 6. Informative References .....................................31 7. Author's Address ...........................................32 8. Full Copyright Statement ...................................33 Perser, Newman, Khurana, Erramilli, Poretsky [Page 2] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 1. Introduction This document describes terminology for the benchmarking of devices that implement traffic control based on IP precedence or diff-serv code point criteria. New terminology is needed because most existing measurements assume the absence of congestion and only a single per-hop- behavior. This document introduces several new terms that will allow measurements to be taken during periods of congestion. Another key difference from existing terminology is the definition of measurements as observed on egress as well as ingress of a device/system under test. Again, the existence of congestion requires the addition of egress measurements as well as those taken on ingress; without observing traffic leaving a device/system it is not possible to say whether traffic-control mechanisms effectively dealt with congestion. The principal measurements introduced in this document are vectors for rate, delay, and jitter, all of which can be observed with or without congestion of the DUT/SUT. This document describes only those terms relevant to measuring behavior of a device or a group of devices using one of these two mechanisms. End-to-end and service-level measurements are beyond the scope of this document. 2. Existing definitions RFC 1242 "Benchmarking Terminology for Network Interconnect Devices" and RFC 2285 "Benchmarking Terminology for LAN Switching Devices" should be consulted before attempting to make use of this document. RFC 2474 "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers" section 2, contains discussions of a number of terms relevant to network-layer traffic control mechanisms and should also be consulted. For the sake of clarity and continuity this RFC adopts the template for definitions set out in Section 2 of RFC 1242. Definitions are indexed and grouped together in sections for ease of reference. 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. Perser, Newman, Khurana, Erramilli, Poretsky [Page 3] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3. Term definitions 3.1 Configuration Terms 3.1.1 Classification Definition: Selection of packets based on the contents of packet header according to defined rules. Discussion: Packets can be selected based on the DS field or IP Precedence in the packet header. Classification can also be based on Multi-Field (MF) criteria such as IP Source and destination addresses, protocol and port number. Classification determines the per-hop behaviors and traffic conditioning functions such as shaping and dropping that are to be applied to the packet. Measurement units: n/a See Also: 3.1.2 Codepoint Set Definition: The set of all DS Code-points or IP precedence values used during the test duration. Discussion: Describes all the code-point markings associated with packets that are input to the DUT/SUT. For each entry in the codepoint set, there are associated vectors describing the rate of traffic, delay, loss, or jitter containing that particular DSCP or IP precedence value. The treatment that a packet belonging to a particular code- point gets is subject to the DUT classifying packets to map to the correct PHB. Moreover, the forwarding treatment in general is also dependent on the complete set of offered vectors. Measurement Units: n/a See Also: Perser, Newman, Khurana, Erramilli, Poretsky [Page 4] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.1.3 Forwarding Congestion Definition: A condition in which one or more egress interfaces are offered more packets than are forwarded. Discussion: This condition is a superset of the overload definition [Ma98]. The overload definition assumes the congestion is introduced strictly by the tester on ingress of a DUT/SUT. That may or may not be the case here. Another difference between Forwarding Congestion and overload occurs when the SUT comprises multiple elements, in that Forwarding Congestion may occur at multiple points. Consider an SUT comprising multiple edge devices exchanging traffic with a single core device. Depending on traffic patterns, the edge devices may induce congestion on multiple egress interfaces on the core device. In contrast, overload [Br91] deals only with overload on ingress. Packet Loss, not increased Delay, is the metric to indicate the condition of Forwarding Congestion. Packet Loss is a deterministic indicator of Forwarding Congestion. While increased delay may be an indicator of Forwarding Congestion, it is a non-deterministic indicator of Forwarding Congestion. External observation of increased delay to indicate congestion is in effect external observation of Incipient Congestion. [Ra99] states that it is impractical to build a black-box test to externally observe Incipient Congestion in a router. For the purpose of "black-box" testing a DUT/SUT, Packet Loss as the indicator of Forwarding Congestion is used. Throughput [Br91] defines the lower boundary of Forwarding Congestion. Throughput is the maximum offered rate with no Forwarding Congestion. At offered rates above throughput, the DUT/SUT is considered congested. Ingress observations alone are not sufficient to cover all cases in which Forwarding Congestion may occur. A device with an infinite amount of memory could buffer an infinite amount of packets, and eventually forward all of them. However, these packets may or may not be forwarded during the test duration. Even though ingress interfaces accept all packets without loss, this hypothetical device may still be congested. Perser, Newman, Khurana, Erramilli, Poretsky [Page 5] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Forwarding Congestion, indicated by occurrence of packet loss, is one type of congestion for a DUT/SUT. Congestion Collapse [Na84] is defined as the state in which buffers are full and all arriving packets must be dropped across the network. Incipient Congestion [Ra99] is defined as congestion that produces increased delay without packet loss. The definition presented here explicitly defines Forwarding Congestion as an event observable on egress interfaces. Regardless of internal architecture, any device that cannot forward packets on one or more egress interfaces is under Forwarding Congestion. Measurement units: none See Also: Gateway Congestion Control Survey [Ma91] 3.1.4 Congestion Management Definition: An implementation of one or more per-hop-behaviors to avoid or minimize the condition of congestion. Discussion: Congestion management may seek either to control congestion or avoid it altogether. Such mechanisms classify packets based upon IP Precedence or DSCP settings in a packet's IP header. Congestion avoidance mechanisms seek to prevent congestion before it actually occurs. Congestion control mechanisms gives one or flows (with a discrete IP Precedence or DSCP value) preferential treatment over other classes during periods of congestion. Measurement units: n/a See Also: 3.1.5 Flow Definition: A flow is a one or more of packets sharing a common intended pair of source and destination interfaces. Perser, Newman, Khurana, Erramilli, Poretsky [Page 6] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Discussion: Packets are grouped by the ingress and egress interfaces they use on a given DUT/SUT. A flow can contain multiple source IP addresses and/or destination IP addresses. All packets in a flow must enter on the same ingress interface and exit on the same egress interface, and have some common network layer content. Microflows [Ni98] are a subset of flows. As defined in [Ni98], microflows require application-to-application measurement. In contrast, flows use lower-layer classification criteria. Since this document focuses on network-layer classification criteria, we concentrate here on the use of network-layer identifiers in describing a flow. Flow identifiers also may reside at the data-link, transport, or application layers of the ISO model. However, identifiers other than those at the network layer are out of scope for this document. A flow may contain a single code point/IP precedence value or may contain multiple values destined for a single egress interface. This is determined by the test methodology. Measurement units: n/a See Also: Microflow [Ni98] Streams 3.2 Measurement Terms 3.2.1 Channel Capacity Definition: The maximum forwarding rate [Ma98] at which none of the offered packets are dropped by the DUT/SUT. Discussion: Channel capacity measures the packet rate at the egress interface(s) of the DUT/SUT. In contrast, throughput as defined in RFC 1242 measures the packet rate is based on the ingress interface(s) of the DUT/SUT. Ingress-based measurements do not account for congestion of the DUT/SUT. Channel capacity, as an egress measurement, does take congestion into account. Perser, Newman, Khurana, Erramilli, Poretsky [Page 7] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Understanding channel capacity is a necessary precursor to any measurement involving congestion. Throughput numbers can be higher than channel capacity because of queueing. This measurement differs from forwarding rate at maximum offered load (FRMOL) [Ma98] in that it is intolerant of loss. Measurement units: N-octet packets per second See Also: Throughput [Br91] Forwarding Rate at Maximum Offered Load [Ma98] 3.2.2 Conforming Definition: Packets which lie within specific rate, delay, or jitter bounds. Discussion: A DUT/SUT may be configured to allow a given traffic class to consume a given amount of bandwidth, or to fall within predefined delay or jitter boundaries. All packets that lie within specified bounds are then said to be conforming, whereas those outside the bounds are nonconforming. Measurement units: n/a See Also: Expected Vector Forwarding Vector Offered Vector Nonconforming 3.2.3 Nonconforming Definition: Packets that do not lie within specific rate, delay, or jitter bounds. Discussion: A DUT/SUT may be configured to allow a given traffic class to consume a given amount of bandwidth, or to fall within predefined delay or jitter boundaries. All packets that do not lie within these bounds are then said to be nonconforming. Perser, Newman, Khurana, Erramilli, Poretsky [Page 8] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Measurement units: n/a See Also: Expected Vector Forwarding Vector Offered Vector Conforming 3.2.4 Delay Definition: The time interval starting when the last bit of the input IP packet reaches the input port of the DUT/SUT and ending when the last bit of the output IP packet is seen on the output port of the DUT/SUT. Discussion: Delay differs from latency [Br91] and one-way delay [Al99] in several key regards: 1. Latency [Br91] assumes knowledge of whether the DUT/SUT uses "store and forward" or "bit forwarding" technology. Delay is delay, regardless of the technology being measured. 2. Delay is a last-in, last-out (LILO) measurement, unlike the last-in, first-out method [Br91] or the first-in, last- out method [Al99]. The LILO method most closely simulates the way a network- layer device actually processes an IP datagram. IP datagrams are not passed up and down the stack unless they are complete, and processing begins only once the last bit of the IP datagram has been received. Further, the LILO method has an additive property, where the sum of the parts MUST equal the whole. This is a key difference from [Br91] and [Al99]. For example, the delay added by two DUTs MUST equal the sum of the delay of the DUTs. This may or may not be the case with [Br91] and [Al99]. 3. Delay measures the IP datagram only, unlike [Br91], which also includes link layer overhead. A metric focused exclusively on the Internet protocol relieves the tester from specifying the start/end for every link layer protocol that IP runs on. This avoids the need to determine whether the start/stop delimiters are included. It also allows the use of heterogeneous link layer protocols in a test. Perser, Newman, Khurana, Erramilli, Poretsky [Page 9] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 4. Delay can be measured at any offered load, whereas latency [Br99] is measured only at the throughput level. For example, non-congested delay may be measured with an offered load that does not exceed the channel capacity, while congested delay may involve an offered load that exceeds channel capacity. 5. Delay SHOULD NOT be used as an absolute indicator of DUT/SUT Forwarding Congestion. While delay may rise when offered load nears or exceeds channel capacity, there is no universal point at which delay can be said to indicate the presence or absence of Forwarding Congestion. Measurement units: Seconds. See Also: Latency [Br91] Latency [Al99] One-way Delay [Br99] 3.2.5 Jitter Definition: The absolute value of the difference between the arrival delay of two consecutive packets belonging to the same stream. Discussion: The delay fluctuation between two consecutive packets in a stream is reported as the jitter. Jitter can be expressed as |D(i) - D(i-1)| where D equals the delay and i is the test sequence number. The measurement does not include lost packets. Jitter can be determined by the ipdv [De02] (IP Delay Variation) by taking the absolute value of the ipdv. The two metrics will produce different mean values. _Mean Jitter_ will produce a positive value, where the _mean ipdv_ is typically zero. Measurement units: Seconds See Also: Jitter variation [Ja99] ipdv [De02] interarrival jitter [Sc96] Perser, Newman, Khurana, Erramilli, Poretsky [Page 10] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.2.6 Undifferentiated Response Definition: The vector(s) obtained when mechanisms used to support diff- serv or IP precedence are disabled. Discussion: Enabling diff-serv or IP precedence mechanisms may impose additional processing overhead for packets. This overhead may degrade performance even when traffic belonging to only one class, the best-effort class, is offered to the device. Measurements with "undifferentiated response" should be made to establish a baseline. The vector(s) obtained with DSCPs or IP precedence enabled can be compared to the undifferentiated response to determine the effect of differentiating traffic. Measurement units: n/a 3.3 Sequence Tracking 3.3.1 In-sequence Packet Definition: A received packet with the expected Test Sequence number. Discussion: In-sequence is done on a stream level. As packets are received on a stream, each packet's Test Sequence number is compared with the previous packet. Only packets that match the expected Test Sequence number are considered in-sequence. Packets that do not match the expected Test Sequence number are counted as _not in-sequence_ or out-of-sequence. Every packet that is received is either in-sequence or out-of- sequence. Subtracting the in-sequence from the received packets (for that stream) can derive the out-of-sequence count. Two types of events will prevent the in-sequence from incrementing: packet loss and reordered packets. Measurement units: Packet count Perser, Newman, Khurana, Erramilli, Poretsky [Page 11] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Stream Test Sequence number 3.3.2 Out-of-order Packet Definition: A received packet with a Test Sequence number less that expected. Discussion: As a stream of packets enter a DUT/SUT, they include a Stream Test Sequence number indicating the order the packets were sent to the DUT/SUT. On exiting the DUT/SUT, these packets may arrive in a different order. Each packet that was re- ordered is counted as an Out-of-order Packet. Certain streaming protocol (such as TCP) require the packets to be in a certain order. Packets outside this are dropped by the streaming protocols even though there were properly received by the IP layer. The type of reordering tolerated by a streaming protocol varies from protocol to protocol, and also by implementation. Out-of-order Packet count is based on the worst case streaming protocol. It allows for no reordering. Packet loss does not affect the Out-of-order Packet count. Only packets that were not received in the order that they were transmitted. Measurement units: Packet count See Also: Stream Test Sequence number 3.3.3 Duplicate Packet Definition: A received packet with a Test Sequence number matching a previously received packet. Discussion: Measurement units: Packet count Perser, Newman, Khurana, Erramilli, Poretsky [Page 12] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Stream Test Sequence number 3.3.4 Stream Definition: A group of packets tracked as a single entity by the traffic receiver. A stream may share a common content such as type (IP, UDP), packet size, or payload. Discussion: Streams are tracked by test sequence number or "unique signature field" (RFC 2889). Streams define how individual packet's statistics are grouped together to form an intelligible summary. Common stream groupings would be by egress interface, destination address, source address, DSCP, or IP precedence. A stream using test sequence numbers can track the ordering of packets as they transverse the DUT/SUT. Streams are not restricted to a pair of source and destination interfaces as long as all packets are tracked as a single entity. A mulitcast stream can be forward to multiple destination interfaces. Measurement units: n/a See Also: Flow MicroFlow [Ni98] Test sequence number 3.3.6 Test Sequence number Definition: A field in the IP payload portion of the packet that is used to verify the order of the packets on the egress of the DUT/SUT. Discussion: The traffic generator sets the test sequence number value and the traffic receiver checks the value upon receipt of the packet. The traffic generator changes the value on each packet transmitted based on an algorithm agreed to by the traffic receiver. Perser, Newman, Khurana, Erramilli, Poretsky [Page 13] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms The traffic receiver keeps track of the sequence numbers on a per stream basis. In addition to number of received packets, the traffic receiver may also report number of in-sequence packets, number of out-sequence packets, number of duplicate packets, and number of reordered packets. The recommended algorithm to use to change the sequence number on sequential packets is an incrementing value. Measurement units: n/a See Also: Stream 3.4 Vectors A vector is a group of packets all containing a specific DSCP or IP precedence value. Vectors are expressed as a pair of numbers. The first is being the particular diff-serv value. The second is the metric expressed as a rate, loss percentage, delay, or jitter. 3.4.1 Intended Vector Definition: A vector describing the rate at which packets having a specific code-point (or IP precedence) that an external source attempts to transmit to a DUT/SUT. Discussion: Intended loads across the different code-point classes determine the metrics associated with a specific code-point traffic class. Measurement Units: N-octets packets per second See Also: Offered Vector Expected Forwarding Vector Expected Loss Vector Expected Sequence Vector Expected Delay Vector Expected Jitter Vector Forwarding Vector Loss Vector Perser, Newman, Khurana, Erramilli, Poretsky [Page 14] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.4.2 Offered Vector Definition: A vector describing the measured rate at which packets having a specific DSCP or IP precedence value are offered to the DUT/SUT. Discussion: Offered loads across the different code-point classes, constituting a code-point set, determine the metrics associated with a specific code-point traffic class. Measurement Units: N-octets packets per second See Also: Expected Forwarding Vector Expected Loss Vector Expected Sequence Vector Expected Delay Vector Expected Jitter Vector Forwarding Vector Codepoint Set 3.4.3 Expected Vectors 3.4.3.1 Expected Forwarding Vector Definition: A vector describing the expected output rate of packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected forwarding vector. Measurement units: N-octet packets per second Perser, Newman, Khurana, Erramilli, Poretsky [Page 15] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Sequence Vector Expected Delay Vector Expected Jitter Vector 3.4.3.2 Expected Loss Vector Definition: A vector describing the percentage of packets, having a specific DSCP or IP precedence value, that should not be forwarded. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected loss vector. Measurement Units: Percentage of intended packets that are expected to be dropped. See Also: Intended Vector Offered Vector Expected Forwarding Vector Expected Sequence Vector Expected Delay Vector Expected Jitter Vector One-way Packet Loss Metric [Ka99] 3.2.3.3 Expected Sequence Vector Definition: A vector describing the expected in-sequence packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Perser, Newman, Khurana, Erramilli, Poretsky [Page 16] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected sequence vector. Measurement Units: N-octet packets per second See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Forwarding Vector Expected Delay Vector Expected Jitter Vector 3.4.3.4 Expected Instantaneous Delay Vector Definition: A vector describing the expected delay for packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected delay vector. Measurement units: Seconds. Perser, Newman, Khurana, Erramilli, Poretsky [Page 17] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Sequence Vector Expected Forwarding Vector Expected Jitter Vector 3.4.3.5 Expected Average Delay Vector Definition: A vector describing the expected average delay for packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected average delay vector. Measurement units: Seconds. See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Sequence Vector Expected Forwarding Vector Expected Jitter Vector 3.4.3.6 Expected Maximum Delay Vector Definition: A vector describing the expected maximum delay for packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Perser, Newman, Khurana, Erramilli, Poretsky [Page 18] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected maximum delay vector. Measurement units: Seconds. See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Sequence Vector Expected Forwarding Vector Expected Jitter Vector 3.4.3.7 Expected Minimum Delay Vector Definition: A vector describing the expected minimum delay for packets having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: The DUT is configured in a certain way in order that service differentiation occurs for a particular DSCP or IP precedence value when a specific traffic mix consisting of multiple DSCPs or IP precedence values are applied. This term attempts to capture the expected forwarding behavior when subjected to a certain offered vectors. The actual algorithm or mechanism the DUT uses to achieve service differentiation is not important in describing the expected minimum delay vector. Measurement units: Seconds. Perser, Newman, Khurana, Erramilli, Poretsky [Page 19] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Intended Vector Offered Vector Output Vectors Expected Loss Vector Expected Sequence Vector Expected Forwarding Vector Expected Jitter Vector 3.2.3.8 Expected Instantaneous Jitter Vector Definition: A vector describing the expected jitter between two consecutive packets' arrival times having a specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: Instantaneous Jitter is the absolute value of the difference between the delay measurement of two packets belonging to the same stream. The delay fluctuation between two consecutive packets in a stream is reported as the "Instantaneous Jitter". Instantaneous Jitter can be expressed as |D(i) - D(i-1)| where D equals the delay and i is the test sequence number. Packets lost are not counted in the measurement. Forwarding Vector may contain several Jitter Vectors. For n packets received in a Forwarding Vector, there is a total of (n-1) Instantaneous Jitter Vectors. Measurement units: Seconds See Also: Delay Jitter Offered Vector Output Vectors Expected Average Jitter Vector Expected Peak-to-peak Jitter Vector Stream Perser, Newman, Khurana, Erramilli, Poretsky [Page 20] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.2.3.9 Expected Average Jitter Vector Definition: A vector describing the expected jitter in packet arrival times for packets having specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: Average Jitter Vector is the average of all the Instantaneous Jitter Vectors measured during the test duration for the same DSCP or IP precedence value. Measurement units: Seconds See Also: Intended Vector Offered Vector Output Vectors Expected Instantaneous Jitter Vector Expected Peak-to-peak Jitter Vector 3.2.3.10 Expected Peak-to-peak Jitter Vector Definition: A vector describing the expected maximum variation in the delay of packet arrival times for packets having specific DSCP or IP precedence value. The value is dependent on the set of offered vectors and configuration of the DUT. Discussion: Peak-to-peak Jitter Vector is the maximum delay minus the minimum delay of the packets (in a vector) forwarded by the DUT/SUT. Peak-to-peak Jitter is not derived from the Instantaneous Jitter Vector. Peak-to-peak Jitter is based upon all the packets during the test duration, not just two consecutive packets. Measurement units: Seconds See Also: Intended Vector Offered Vector Output Vectors Expected Instantaneous Jitter Vector Expected Average Jitter Vector Perser, Newman, Khurana, Erramilli, Poretsky [Page 21] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.4.4 Output Vectors 3.4.4.1 Forwarding Vector Definition: The number of packets per second for all packets containing a specific DSCP or IP precedence value that a device can be observed to successfully forward to the correct destination interface in response to an offered vector. Discussion: Forwarding Vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND the packets per second value combine to make a vector. The Forwarding Vector represents packet rate based on its specific DSCP (or IP precedence) value. It is not necessarily based on a stream or flow. The Forwarding Vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Forwarding Vector. Forwarding Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP (or IP precedence) value for a multiple-hop measurement. Measurement units: N-octet packets per second See Also: Intended Vector Offered Vector Expected Vectors Loss Vector Sequence Vector Delay Vectors 3.4.4.2 Loss Vector Definition: The percentage of packets containing specific DSCP or IP precedence value that a DUT/SUT did not transmit to the correct destination interface in response to an offered vector. Discussion: Loss Vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND the percentage value combine to make a vector. Perser, Newman, Khurana, Erramilli, Poretsky [Page 22] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms The Loss Vector represents percentage based on a specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Loss Vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Loss Vector Loss Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Measurement Units: Percentage of offered packets that are not forwarded. See Also: Intended Vector Offered Vector Expected Vectors Forwarding Vector Sequence Vector Delay Vectors One-way Packet Loss Metric [Ka99] 3.4.4.3 Sequence Vector Definition: The number of packets per second for all packets containing a specific DSCP or IP precedence value that a device can be observed to transmit in sequence to the correct destination interface in response to an offered vector. Discussion: Sequence Vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND the packets per second value combine to make a vector. The Sequence Vector represents packet rate based on its specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Sequence Vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Sequence Vector. Sequence Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Measurement Units: N-octet packets per second Issues: Perser, Newman, Khurana, Erramilli, Poretsky [Page 23] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: In-sequence Packet Intended Vector Offered Vector Expected Vectors Loss Vector Forwarding Vector Delay Vectors 3.4.4.4 Instantaneous Delay Vector Definition: The delay for a packet containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Instantaneous Delay vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND delay value combine to make a vector. The Instantaneous Delay Vector represents delay on its specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Delay vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Delay vectors. Instantaneous Delay Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Instantaneous Delay vector can be obtained at any offered load. Recommend at or below the channel capacity in the absence of congestion. For congested delay, run the offered load above the channel capacity. Forwarding Vector may contain several Instantaneous Delay Vectors. For every packet received in a Forwarding Vector, there is a corresponding Instantaneous Delay Vector. Measurement Units: Seconds See Also: Delay Intended Vector Offered Vector Expected Delay Vectors Average Delay Vector Maximum Delay Vector Minimum Delay Vector Perser, Newman, Khurana, Erramilli, Poretsky [Page 24] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.4.4.5 Average Delay Vector Definition: The average delay for packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Average Delay vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND delay value combine to make a vector. The Delay Vector represents delay on its specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Delay vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Delay vector. The Average Delay Vector is computed by averaging all the Instantaneous Delay Vectors for a given vector. Average Delay Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Average Delay vector can be obtained at any offered load. Recommend at or below the channel capacity in the absence of congestion. For congested delay, run the offered load above the channel capacity. Measurement Units: Seconds See Also: Delay Intended Vector Offered Vector Expected Delay Vectors Instantaneous Delay Vector Maximum Delay Vector Minimum Delay Vector Perser, Newman, Khurana, Erramilli, Poretsky [Page 25] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 3.4.4.6 Maximum Delay Vector Definition: The maximum delay from all packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Maximum Delay vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND delay value combine to make a vector. The Maximum Delay Vector represents delay on its specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Maximum Delay vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Delay vector. Maximum Delay Vector is based upon the maximum Instantaneous Delay Vector of all packets in a Forwarding Vector. Maximum Delay Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Measurement Units: Seconds See Also: Delay Intended Vector Offered Vector Expected Delay Vectors Instantaneous Delay Vector Forwarding Vector Average Delay Vector Minimum Delay Vector 3.4.4.7 Minimum Delay Vector Definition: The minimum delay from all packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Delay vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND delay value combine to make a vector. Perser, Newman, Khurana, Erramilli, Poretsky [Page 26] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms The Minimum Delay Vector represents delay on its specific DSCP or IP precedence value. It is not necessarily based on a stream or flow. The Minimum Delay vector may be expressed as per port of the DUT/SUT. However, it must be consistent with the Expected Delay vector. Minimum Delay Vector is based upon the minimum Instantaneous Delay Vector of all packets in a Forwarding Vector. Minimum Delay Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Minimum Delay vector can be obtained at any offered load. Recommend at or below the channel capacity in the absence of congestion. For congested delay, run the offered load above the channel capacity. Measurement Units: Seconds See Also: Delay Intended Vector Offered Vector Expected Delay Vectors Instantaneous Delay Vector Forwarding Vector Average Delay Vector Maximum Delay Vector 3.4.4.8 Instantaneous Jitter Vector Definition: The jitter for two consecutive packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Instantaneous Jitter is the absolute value of the difference between the delay measurement of two packets belonging to the same stream. Jitter vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND jitter value combine to make a vector. Perser, Newman, Khurana, Erramilli, Poretsky [Page 27] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms The delay fluctuation between two consecutive packets in a stream is reported as the "Instantaneous Jitter". Instantaneous Jitter Vector can be expressed as |D(i) - D(i- 1)| where D equals the delay and i is the test sequence number. Packets lost are not counted in the measurement. Instantaneous Jitter Vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Forwarding Vector may contain several Instantaneous Jitter Vectors. For n packets received in a Forwarding Vector, there are exactly (n-1) Instantaneous Jitter Vectors. Measurement units: Seconds See Also: Delay Jitter Forwarding Vector Stream Expected Vectors Average Jitter Vector Peak-to-peak Jitter Vector 3.4.4.9 Average Jitter Vector Definition: The average jitter for packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Average Jitter Vector is the average of all the Instantaneous Jitter Vectors of the same DSCP or IP precedence value, measured during the test duration. Average Jitter vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND jitter value combine to make a vector. Average Jitter vector is a per-hop measurement. The DUT/SUT may change the specific DSCP or IP precedence value for a multiple-hop measurement. Measurement units: Seconds Perser, Newman, Khurana, Erramilli, Poretsky [Page 28] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms See Also: Jitter Forwarding Vector Stream Expected Vectors Instantaneous Jitter Vector Peak-to-peak Jitter Vector 3.4.4.10 Peak-to-peak Jitter Vector Definition: The maximum possible variation in the delay for packets containing specific DSCP or IP precedence value that a device can be observed to successfully transmit to the correct destination interface in response to an offered vector. Discussion: Peak-to-peak Jitter Vector is the maximum delay minus the minimum delay of the packets (in a vector) forwarded by the DUT/SUT. Jitter vector is expressed as pair of numbers. Both the specific DSCP (or IP precedence) value AND jitter value combine to make a vector. Peak-to-peak Jitter is not derived from the Instantaneous Jitter Vector. Peak-to-peak Jitter is based upon all the packets during the test duration, not just two consecutive packets. Measurement units: Seconds See Also: Jitter Forwarding Vector Stream Expected Vectors Average Jitter Vector Peak-to-peak Jitter Vector Perser, Newman, Khurana, Erramilli, Poretsky [Page 29] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 4. Security Considerations Documents of this type do not directly affect the security of the Internet or of corporate networks as long as benchmarking is not performed on devices or systems connected to production networks. Packets with unintended and/or unauthorized DSCP or IP precedence values may present security issues. Determining the security consequences of such packets is out of scope for this document. 5. Normative References [Br91] Bradner, S., Editor, "Benchmarking Terminology for Network Interconnection Devices", RFC 1242, July 1991. [Ma98] Mandeville, R., "Benchmarking Terminology for LAN Switching Devices", RFC 2285, February 1998. [Ni98] K. Nichols, S. Blake, F. Baker, D. Black,"Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998. Perser, Newman, Khurana, Erramilli, Poretsky [Page 30] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 6. Informative References [Al99] Almes, G., Kalidindi, S., Zekauskas, M., _A One-way Delay Metric for IPPM_, RFC 2679, September 1999 [Bl98] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [Br99] Bradner, S., McQuaid, J. _Benchmarking Methodology for Network Interconnect Devices_, RFC 2544, March 1999 [De02] C. Demichelis, P. Chimento, _IP Packet Delay Variation Metric for IPPM_, RFC 3393, November 2002 [Ja99] V. Jacobson, K. Nichols, K. Poduri, _An Expedited Forwarding PHB_, RFC 2598, June 1999 [Ka99] Almes, G., Kalidindi, S., Zekauskas, M., _A One-way Packet Loss Metric for IPPM_, RFC 2680, September 1999 [Ma91] A. Mankin, K. Ramakrishnan, _Gateway Congestion Control Survey_, RFC 1254, August 1991 [Na84] Nagle, John, "Congestion Control in IP/TCP Internetworks", RFC 896, January 1984. [Ra99] Ramakrishnan, K. and Floyd, S., "A Proposal to add Explicit Congestion Notification (ECN) to IP", RFC 2481, January 1999. [Sc96] H. Schulzrinne, GMD Fokus, S. Casner, R. Frederick, V. Jacobson, _RTP: A Transport Protocol for Real-Time Applications_, RFC 1889, January 1996 Perser, Newman, Khurana, Erramilli, Poretsky [Page 31] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 7. Authors' Address Jerry Perser Spirent Communications 26750 Agoura Road Calabasas, CA 91302 USA Phone: + 1 818 676 2300 EMail: jerry.perser@spirentcom.com David Newman Network Test 31324 Via Colinas, Suite 113 Westlake Village, CA 91362 USA Phone: + 1 818 889 0011, x10 EMail: dnewman@networktest.com Sumit Khurana Telcordia Technologies 445 South Street Morristown, NJ 07960 USA Phone: + 1 973 829 3170 EMail: sumit@research.telcordia.com Shobha Erramilli QNetworx Inc 1119 Campus Drive West Morganville NJ 07751 USA Phone: EMail: shobha@qnetworx.com Scott Poretsky Avici Systems 101 Billerica Ave_Building #6 N. Billerica, MA 01862 USA Phone: + 1 978 964 2287 EMail: sporetsky@avici.com Perser, Newman, Khurana, Erramilli, Poretsky [Page 32] INTERNET-DRAFT Terminology for Benchmarking February 2003 Network-layer Traffic Control Mechanisms 8. Full Copyright Statement Copyright (C) The Internet Society (1998). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Perser, Newman, Khurana, Erramilli, Poretsky [Page 33]