INTERNET-DRAFT N. Elkins Inside Products R. Hamilton Chemical Abstracts Service M. Ackermann Intended Status: Proposed Standard BCBS Michigan Expires: April 2015 October 20, 2014 IPPM Considerations for the IPv6 PDM Destination Option draft-elkins-ippm-pdm-option-02 Table of Contents 1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 End User Quality of Service (QoS) . . . . . . . . . . . . . 3 1.3 Need for a Packet Sequence Number . . . . . . . . . . . . . 4 1.4 Rationale for proposed solution . . . . . . . . . . . . . . 4 2 Measurement Information Derived from PDM . . . . . . . . . . . 5 2.1 Round-Trip Delay . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Server Delay . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Performance and Diagnostic Metrics Destination Option Layout . . 6 3.1 Destination Options Header . . . . . . . . . . . . . . . . 6 3.2 Performance and Diagnostic Metrics Destination Option . . . 6 4 Considerations of Timing Representation . . . . . . . . . . . . 9 4.1 Encoding the Delta-Time Values . . . . . . . . . . . . . . . 9 4.2 Timer registers are different on different hardware . . . . 9 4.3 Timer Units on Other Systems . . . . . . . . . . . . . . . . 10 4.4 Time Base . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.5 Timer-value scaling . . . . . . . . . . . . . . . . . . . . 10 4.6 Limitations with this encoding method . . . . . . . . . . . 12 4.7 Lack of precision induced by timer value truncation . . . . 12 5 Sample Implementation Flow PDM . . . . . . . . . . . . . . . . . 13 5.1 Step 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2 Step 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3 Step 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.4 Step 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.5 Step 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6 Security Considerations . . . . . . . . . . . . . . . . . . . . 17 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 17 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.1 Normative References . . . . . . . . . . . . . . . . . . . . 18 8.2 Informative References . . . . . . . . . . . . . . . . . . . 18 9 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Elkins Expires April 23, 2015 [Page 1] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 Abstract To assess performance problems, measurements based on optional sequence numbers and timing may be embedded in each packet. Such measurements may be interpreted in real-time or after the fact. An implementation of the existing IPv6 Destination Options extension header, the Performance and Diagnostic Metrics (PDM) Destination Options extension header has been proposed in a companion document. This document specifies the field limits, calculations, and usage of the PDM in measurement. 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) 2014 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 (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 Elkins Expires April 23, 2015 [Page 2] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 1 Background To assess performance problems, measurements based on optional sequence numbers and timing may be embedded in each packet. Such measurements may be interpreted in real-time or after the fact. An implementation of the existing IPv6 Destination Options extension header, the Performance and Diagnostic Metrics (PDM) Destination Options extension header has been proposed in a companion document. This document specifies the field limits, calculations, and usage of the PDM in measurement. 1.1 Terminology 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]. 1.2 End User Quality of Service (QoS) The difference between timing values in the PDM traveling along with the packet will be used to estimate QoS as experienced by an end user device. For many applications, the key user performance indicator is response time. When the end user is an individual, he is generally indifferent to what is happening along the network; what he really cares about is how long it takes to get a response back. But this is not just a matter of individuals' personal convenience. In many cases, rapid response is critical to the business being conducted. When the end user is a device (e.g. with the Internet of Things), what matters is the speed with which requested data can be transferred -- specifically, whether the requested data can be transferred in time to accomplish the desired actions. This can be important when the relevant external conditions are subject to rapid change. Response time and consistency are not just "nice to have". On many networks, the impact can be financial hardship or endanger human life. In some cities, the emergency police contact system operates over IP, law enforcement uses TCP/IP networks, transactions on our stock exchanges are settled using IP networks. The critical nature of such activities to our daily lives and financial well-being demand a solution. Elkins Expires April 23, 2015 [Page 3] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 1.3 Need for a Packet Sequence Number While performing network diagnostics of an end-to-end connection, it often becomes necessary to find the device along the network path creating problems. Diagnostic data may be collected at multiple places along the path (if possible), or at the source and destination. Then, the diagnostic data corresponding to each packet at different observation points must be matched for proper measurements. A sequence number in each packet provides sufficient basis for the matching process. If need be, the timing fields may be used along with the sequence number to ensure uniqueness. This method of data collection along the path is of special use to determine where packet loss or packet corruption is happening. The packet sequence number needs to be unique in the context of the session (5-tuple). 1.4 Rationale for proposed solution The current IPv6 specification does not provide timing nor a similar field in the IPv6 main header or in any extension header. So, we propose the IPv6 Performance and Diagnostic Metrics destination option (PDM) [ELK-PDM]. Advantages include: 1. Real measure of actual transactions. 2. Independence from transport layer protocols. 3. Ability to span organizational boundaries with consistent instrumentation 4. No time synchronization needed between session partners The PDM provides the ability to quickly determine if the (latency) problem is in the network or in the server (application). More intermediate measurements may be needed if the host or network discrimination is not sufficient. At the client, TCP/IP stack time vs. applications time may still need to be broken out by client software. Elkins Expires April 23, 2015 [Page 4] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 2 Measurement Information Derived from PDM Each packet contains information about the sender and receiver. In IP protocol, the identifying information is called a "5-tuple". The 5-tuple consists of: SADDR : IP address of the sender SPORT : Port for sender DADDR : IP address of the destination DPORT : Port for destination PROTC : Protocol for upper layer (ex. TCP, UDP, ICMP, etc.) The PDM contains the following metrics: PSNTP : Packet Sequence Number This Packet PSNLR : Packet Sequence Number Last Received DELTALR : Delta Last Received PSNLS : Packet Sequence Number Last Sent DELTALS : Delta Last Sent This information, combined with the 5-tuple, allows the measurement of the following metrics: 1. Round-trip delay 2. Server delay 2.1 Round-Trip Delay Round-trip delay is the end-to-end delay for a packet from a source host to a destination host. This measurement has been defined, and the advantages and disadvantages discussed in "A Round-trip Delay Metric for IPPM" [RFC2681]. 2.2 Server Delay Server delay is the interval between when a packet is received by a device and the first corresponding packet is sent back in response. This may be "Server Processing Time". It may also be a delay caused by acknowledgements. Server processing time includes the time taken by the combination of the stack and application to return the response. The stack delay may be related to network performance. If this aggregate time is seen as a problem, and there is a need to make a clear distinction between application processing time and stack delay, including that caused by the network, then more client based measurements are needed. Elkins Expires April 23, 2015 [Page 5] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 3 Performance and Diagnostic Metrics Destination Option Layout 3.1 Destination Options Header The IPv6 Destination Options Header is used to carry optional information that need be examined only by a packet's destination node(s). The Destination Options Header is identified by a Next Header value of 60 in the immediately preceding header and is defined in RFC2460 [RFC2460]. The IPv6 Performance and Diagnostic Metrics Destination Option (PDM) is an implementation of the Destination Options Header (Next Header value = 60). The PDM does not require time synchronization. 3.2 Performance and Diagnostic Metrics Destination Option The IPv6 Performance and Diagnostic Metrics Destination Option (PDM) contains the following fields: TIMEBASE : Base timer unit SCALEDL : Scale for Delta Last Received SCALEDS : Scale for Delta Last Sent PSNTP : Packet Sequence Number This Packet PSNLR : Packet Sequence Number Last Received DELTALR : Delta Last Received DELTALS : Delta Last Sent The PDM destination option is encoded in type-length-value (TLV) format as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length |TB |ScaleDL | ScaleDS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PSN This Packet | PSN Last Received | |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Delta Last Received | Delta Last Sent | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option Type TBD = 0xXX (TBD) [To be assigned by IANA] [RFC2780] Option Length 8-bit unsigned integer. Length of the option, in octets, excluding the Option Type and Option Length fields. This field MUST be set to 16. Elkins Expires April 23, 2015 [Page 6] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 Time Base 2-bit unsigned integer. It will indicate the lowest granularity possible for this device. That is, for a value of 00 in the Time Base field, a value of 1 in the DELTA fields indicates 1 picosecond. This field is being included so that a device may choose the granularity which most suits its timer ticks. That is, so that it does not have to do more work than needed to convert values required for the PDM. The possible values of Time Base are as follows: 00 - milliseconds 01 - microseconds 10 - nanoseconds 11 - picoseconds Scale Delta Last Received (SCALEDLR) 7-bit signed integer. This is the scaling value for the Delta Last Received (DELTALR) field. The possible values are from -128 to +127. See Section 4 for further discussion on Timing Considerations and formatting of the scaling values. Scale Delta Last Sent (SCALEDLS) 7-bit signed integer. This is the scaling value for the Delta Last Sent (DELTALS) field. The possible values are from -128 to +127. Packet Sequence Number This Packet (PSNTP) 16-bit unsigned integer. This field will wrap. It is intended for human use. That is, while to be used while analyzing packet traces. Initialized at a random number and monotonically incremented for each packet on the 5-tuple. The 5-tuple consists of the source and destination IP addresses, the source and destination ports, and the upper layer protocol (ex. TCP, ICMP, etc). The random number initialization is to make it harder to spoof and insert such packets. Operating systems MUST implement a separate packet sequence number counter per 5-tuple. Operating systems MUST NOT implement a single counter for all connections. Elkins Expires April 23, 2015 [Page 7] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 Packet Sequence Number Last Received (PSNLR) 16-bit unsigned integer. This is the PSN of the packet last received on the 5-tuple. Delta Last Received (DELTALR) A 16-bit unsigned integer field. The value is according to the scale in SCALEDLR. DELTALR = Send time packet 2 - Receive time packet 1 Delta Last Sent (DELTALS) A 16-bit unsigned integer field. The value is according to the scale in SCALEDS. Delta Last Sent = Receive time packet 2 - Send time packet 1 Option Type The two highest-order bits of the Option Type field are encoded to indicate specific processing of the option; for the PDM destination option, these two bits MUST be set to 00. This indicates the following processing requirements: 00 - skip over this option and continue processing the header. RFC2460 [RFC2460] defines other values for the Option Type field. These MUST NOT be used in the PDM. The other values are as follows: 01 - discard the packet. 10 - discard the packet and, regardless of whether or not the packet's Destination Address was a multicast address, send an ICMP Parameter Problem, Code 2, message to the packet's Source Address, pointing to the unrecognized Option Type. 11 - discard the packet and, only if the packet's Destination Address was not a multicast address, send an ICMP Parameter Problem, Code 2, message to the packet's Source Address, pointing to the unrecognized Option Type. In keeping with RFC2460 [RFC2460], the third-highest-order bit of the Option Type specifies whether or not the Option Data of that option Elkins Expires April 23, 2015 [Page 8] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 can change en-route to the packet's final destination. In the PDM, the value of the third-highest-order bit MUST be 0. The possible values are as follows: 0 - Option Data does not change en-route 1 - Option Data may change en-route The three high-order bits described above are to be treated as part of the Option Type, not independent of the Option Type. That is, a particular option is identified by a full 8-bit Option Type, not just the low-order 5 bits of an Option Type. 4 Considerations of Timing Representation 4.1 Encoding the Delta-Time Values This section makes reference to and expands on the document "Encoding of Time Intervals for the TCP Timestamp Option" [TRAM-TCPM]. 4.2 Timer registers are different on different hardware One of the problems with timestamp recording is the variety of hardware that generates the time value to be used. Different CPUs track the time in registers of different sizes, and the most- frequently-iterated bit could be the first on the left or the first on the right. In order to generate some examples here it is necessary to indicate the type of timer register being used. As described in the "IBM z/Architecture Principles of Operation" [IBM-POPS], the Time-Of-Day clock in a zSeries CPU is a 104-bit register, where bit 51 is incremented approximately every microsecond: 1 0 1 2 3 4 5 6 0 +--------+---------+---------+---------+---------+---------+--+...+ | | | | | |* | | +--------+---------+---------+---------+---------+---------+--+...+ ^ ^ ^ 0 51 = 1 usec 103 To represent these values concisely a hexadecimal representation will be used, where each digit represents 4 binary bits. Thus: 0000 0000 0000 0001 = 1 timer unit (2**-12 usec, or about 244 psec) 0000 0000 0000 1000 = 1 microsecond Elkins Expires April 23, 2015 [Page 9] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 0000 0000 003E 8000 = 1 millisecond 0000 0000 F424 0000 = 1 second 0000 0039 3870 0000 = 1 minute 0000 0D69 3A40 0000 = 1 hour 0001 41DD 7600 0000 = 1 day Note that only the first 64 bits of the register are commonly represented, as that represents a count of timer units on this hardware. Commonly the first 52 bits are all that are displayed, as that represents a count of microseconds. 4.3 Timer Units on Other Systems This encoding method works the same with other hardware clock formats. The method uses a microsecond as the basic value and allows for large time differentials. 4.4 Time Base We propose a base unit for the time. This is a 2-bit integer indicating the lowest granularity possible for this device. That is, for a value of 00 in the Time Base field, a value of 1 in the DELTA fields indicates 1 picosecond. The possible values of Time Base are as follows: 00 - milliseconds 01 - microseconds 10 - nanoseconds 11 - picoseconds Time base is not necessarily equivalent to length of one timer tick. That is, on many, if not all, systems, the timer tick value will not be in complete units of nanoseconds, milliseconds, etc. For example, on an IBM zSeries machine, one timer tick (or clock unit) is 2 to the -12th microseconds. Therefore, some amount of conversion may be needed to approximate Time Base units. 4.5 Timer-value scaling As discussed in [TRAM-TCPM] we propose storing not an entire time- interval value, but just the most significant bits of that value, along with a scaling factor to indicate the magnitude of the time- interval value. In our case, we will use the high-order 16 bits. The Elkins Expires April 23, 2015 [Page 10] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 scaling value will be the number of bits in the timer register to the right of the 16th significant bit. That is, if the timer register contains this binary value: 1110100011010100101001010001000000000000 <-16 bits -><-24 bits -> then, the values stored would be 1110 1000 1101 0100 in binary (E8D4 hexadecimal) for the time value and 24 for the scaling value. Note that the displayed value is the binary equivalent of 1 second expressed in picoseconds. The below table represents a device which has a TimeBase of picosecond (or 00). The smallest and simplest value to represent is 1 picosecond; the time value stored is 1, and the scaling value is 0. Using values from the table below, we have: Time value in Encoded Scaling Delta time picoseconds value decimal -------------------------------------------------------- 1 picosecond 1 1 0 1 nanosecond 3E8 3E8 0 1 microsecond F4240 F424 4 1 millisecond 3B9ACA00 3B9A 16 1 second E8D4A51000 E8D4 24 1 minute 3691D6AFC000 3691 32 1 hour cca2e51310000 CCA2 36 1 day 132f4579c980000 132F 44 365 days 1b5a660ea44b80000 1B5A 52 Sample binary values (high order 16 bits taken) 1 psec 1 0001 1 nsec 3E8 0011 1110 1000 1 usec F4240 1111 0100 0010 0100 0000 1 msec 3B9ACA00 0011 1011 1001 1010 1100 1010 0000 0000 1 sec E8D4A51000 1110 1000 1101 0100 1010 0101 0001 0000 0000 0000 Elkins Expires April 23, 2015 [Page 11] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 4.6 Limitations with this encoding method If we follow the specification in [TRAM-TCPM], the size of one of these time-interval fields is limited to this 11-bit value and five- bit scale, so that they fit into a 16-bit space. With that limitation, the maximum value that could be stored in 16 bits is: 11-bit value Scale ============= ====== 1111 1111 111 1 1111 or an encoded value of 3FF and a scale value of 31. This value corresponds to any time differential between: || 11 1111 1111 1000 0000 0000 0000 0000 0000 0000 0000 (binary) 3 F F 8 0 0 0 0 0 0 0 (hexadecimal) and 11 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 (binary) 3 F F F F F F F F F F (hexadecimal) This time value, 3FFFFFFFFFF, converts to 50 days, 21 hours, 40 minutes and 46.511103 seconds. A time differential 1 microsecond longer won't fit into 16 bits using this encoding method. 4.7 Lack of precision induced by timer value truncation When the bit values following the first 11 significant bits are truncated, obviously loss of precision in the value. The range of values that will be truncated to the same encoded value is 2**(Scale)-1 microseconds. The smallest time differential value that will be truncated is 1000 0000 0000 = 2.048 msec The value 1000 0000 0001 = 2.049 msec will be truncated to the same encoded value, which is 400 in hex, with a scale value of 1. With the scale value of 1, the value range is calculated as 2**1 - 1, or 1 usec, which you can see is the difference between these minimum and maximum values. Elkins Expires April 23, 2015 [Page 12] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 With that in mind, let's look at that table of delta time values again, where the Precision is the range from the smallest value corresponding to this encoded value to the largest: Time value in Encoded Delta time microseconds value Scale Precision 1 microsecond 1 1 0 0:00.000000 1 millisecond 38E 38E 0 0:00.000000 1 second F4240 7A1 9 0:00.000511 1 minute 3938700 727 15 0:00.032767 1 hour D693A400 6B4 21 0:02.097151 1 day 141DD76000 507 26 1:07.108863 Maximum value 3FFFFFFFFFF 7FF 31 35:47.483647 So, when measuring the delay between transmission of two packets, or between the reception of two packets, any delay shorter than 50 days 21 hours and change can be stored in this encoded fashion within 16 bits. When you encode, for example, a DTN response time delay of 50 days, 21 hours and 40 minutes, you can be assured of accuracy within 35 minutes. 5 Sample Implementation Flow PDM Following is a sample simple flow for the PDM with one packet sent from Host A and one packet received by Host B. The PDM does not require time synchronization between Host A and Host B. The calculations to derive meaningful metrics for network diagnostics are shown below each packet sent or received. Each packet, in addition to the PDM contains information on the sender and receiver. As discussed before, a 5-tuple consists of: SADDR : IP address of the sender SPORT : Port for sender DADDR : IP address of the destination DPORT : Port for destination PROTC : Protocol for upper layer (ex. TCP, UDP, ICMP) It should be understood that the packet identification information is in each packet. We will not repeat that in each of the following steps. Elkins Expires April 23, 2015 [Page 13] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 5.1 Step 1 Packet 1 is sent from Host A to Host B. The time for Host A is set initially to 10:00AM. The time and packet sequence number are saved by the sender internally. The packet sequence number and delta times are sent in the packet. Packet 1 +----------+ +----------+ | | | | | Host | ----------> | Host | | A | | B | | | | | +----------+ +----------+ PDM Contents: PSNTP : Packet Sequence Number This Packet: 25 PSNLR : Packet Sequence Number Last Received: - DELTALR : Delta Last Received: - SCALEDL : Scale of Delta LR: 0 DELTALS : Delta Last Sent: - SCALEDS : Scale of Delta LS: 0 TIMEBASE : Granularity of Time: 00 (Picoseconds) Internally, within the sender, Host A, it must keep: Packet Sequence Number of the last packet sent: 25 Time the last packet was sent: 10:00:00 Note, the initial PSNTP from Host A starts at a random number. In this case, 25. The timestamp is in seconds for the sake of simplicity. 5.2 Step 2 Packet 1 is received at Host B. Its time is set to one hour later than Host A. In this case, 11:00AM Internally, within the receiver, Host B, it must note: Packet Sequence Number of the last packet received: 25 Time the last packet was received : 11:00:03 Elkins Expires April 23, 2015 [Page 14] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 Note, this timestamp is in Host B time. It has nothing whatsoever to do with Host A time. The Packet Sequence Number of the last packet received will become PSNLR which will be sent out in the packet sent by Host B in the next step. The time last received will be used to calculate the DELTALR value to be sent out in the packet sent by Host B in the next step. 5.3 Step 3 Packet 2 is sent by Host B to Host A. Note, the initial packet sequence number (PSNTP) from Host B starts at a random number. In this case, 12. Before sending the packet, Host B does a calculation of deltas. Since Host B knows when it is sending the packet, and it knows when it received the previous packet, it can do the following calculation: Sending time (packet 2) - receive time (packet 1) We will call the result of this calculation: Delta Last Received That is: DELTALR = Sending time (packet 2) - receive time (packet 1) Note, both sending time and receive time are saved internally in Host B. They do not travel in the packet. Only the Delta is in the packet. Assume that within Host B is the following: Packet Sequence Number of the last packet received: 25 Time the last packet was received: 11:00:03 Packet Sequence Number of this packet: 12 Time this packet is being sent: 11:00:07 We can now calculate a delta value to be sent out in the packet. DELTALR becomes: 4 seconds = 11:00:07 - 11:00:03 This is the derived metric: Server Delay. The time and scaling factor must be calculated. Then, this value, along with the packet sequence numbers will be sent to Host A as follows: Elkins Expires April 23, 2015 [Page 15] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 Packet 2 +----------+ +----------+ | | | | | Host | <---------- | Host | | A | | B | | | | | +----------+ +----------+ PDM Contents: PSNTP : Packet Sequence Number This Packet: 12 PSNLR : Packet Sequence Number Last Received: 25 DELTALR : Delta Last Received: 3A35 (4 seconds) SCALEDL : Scale of Delta LR: 25 DELTALS : Delta Last Sent: - SCALEDS : Scale of Delta LS: 0 TIMEBASE : Granularity of Time: 00 (Picoseconds) The metric left to be calculated is the Round-Trip Delay. This will be calculated by Host A when it receives Packet 2. 5.4 Step 4 Packet 2 is received at Host A. Remember, its time is set to one hour earlier than Host B. Internally, it must note: Packet Sequence Number of the last packet received: 12 Time the last packet was received : 10:00:12 Note, this timestamp is in Host A time. It has nothing whatsoever to do with Host B time. So, now, Host A can calculate total end-to-end time. That is: End-to-End Time = Time Last Received - Time Last Sent For example, packet 25 was sent by Host A at 10:00:00. Packet 12 was received by Host A at 10:00:12 so: End-to-End time = 10:00:12 - 10:00:00 or 12 (Server and Network RT delay combined) This derived metric we will call DELTALS or Delta Last Sent. Elkins Expires April 23, 2015 [Page 16] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 We can now also calculate round trip delay. The formula is: Round trip delay = DELTALS - DELTALR Or: Round trip delay = 12 - 4 or 8 Now, the only problem is that at this point all metrics are in Host A only and not exposed in a packet. To do that, we need a third packet. 5.5 Step 5 Packet 3 is sent from Host A to Host B. +----------+ +----------+ | | | | | Host | ----------> | Host | | A | | B | | | | | +----------+ +----------+ PDM Contents: PSNTP : Packet Sequence Number This Packet: 26 PSNLR : Packet Sequence Number Last Received: 12 DELTALR : Delta Last Received: 0 SCALEDL : Scale of Delta LR 0 DELTALS : Delta Last Sent: 105e (12 seconds) SCALEDL : Scale of Delta LR 26 TIMEBASE : Granularity of Time: 00 (Picoseconds) To calculate Two-Way Delay, any packet capture device may look at these packets and do what is necessary. 6 Security Considerations TBD. It is conceivable that in allowing this Destination Option through a firewall, that other malicious traffic may be allowed through. 7 IANA Considerations Option Type TBD = 0xXX (TBD) [To be assigned by IANA] [RFC2780]. Elkins Expires April 23, 2015 [Page 17] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 8 References 8.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, September 1999. [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers", BCP 37, RFC 2780, March 2000. [IBM-POPS] IBM Corporation, "IBM z/Architecture Principles of Operation", SA22-7832, 1990-2012 8.2 Informative References [ELK-PDM] Elkins, N., "draft-elkins-6man-ipv6-pdm-dest-option-09", Internet Draft, October 2014. [Work in Progress] [TRAM-TCPM] Trammel, B., "Encoding of Time Intervals for the TCP Timestamp Option-01", Internet Draft, July 2013. [Work in Progress] 9 Acknowledgments The authors would like to thank Keven Haining, Al Morton, Brian Trammel, David Boyes, and Rick Troth for their comments and assistance. Authors' Addresses Nalini Elkins Inside Products, Inc. 36A Upper Circle Carmel Valley, CA 93924 United States Phone: +1 831 659 8360 Email: nalini.elkins@insidethestack.com http://www.insidethestack.com Robert Hamilton Chemical Abstracts Service A Division of the American Chemical Society Elkins Expires April 23, 2015 [Page 18] INTERNET DRAFT elkins-ippm-pdm-metrics-02 October 20, 2014 2540 Olentangy River Road Columbus, Ohio 43202 United States Phone: +1 614 447 3600 x2517 Email: rhamilton@cas.org http://www.cas.org Michael S. Ackermann Blue Cross Blue Shield of Michigan P.O. Box 2888 Detroit, Michigan 48231 United States Phone: +1 310 460 4080 Email: mackermann@bcbsmi.com http://www.bcbsmi.com Elkins Expires April 23, 2015 [Page 19]