RFC 7799

Active and Passive Metrics and Methods (with Hybrid Types In-Between)

📅 published May 2016, from ietf

Internet Engineering Task Force (IETF) ✨

Okay bestie, let's get into RFC 7799! 🎀 It's titled Active and Passive Metrics and Methods (with Hybrid Types In-Between) 🦋 and it was written by A. Morton from AT&T Labs 💅. It came out in May 2016 🌸. The category is Informational, so it's not a Standards Track spec, just a super helpful explainer 🧚. It doesn't obsolete or update any other RFCs 💖.

Abstract ✨

Okay so this memo gives really clear definitions for Active and Passive performance assessment 🔥. Metrics and Methods can be built as either "Active" or "Passive" 💜. Some methods mix bits of both, and we call those "Hybrid Methods" 🦋. It also gives you a bunch of dimensions to help you evaluate brand-new methods as they show up, which is so useful 😭🫶.

Status of This Memo ✨

Bestie, this document is not an Internet Standards Track spec 💅. It's published just for information 🌈.

This is a product of the IETF 🎀. It represents the consensus of the IETF community, received public review, and was approved for publication by the Internet Engineering Steering Group (IESG) 👑. Not every IESG-approved document is a candidate for any level of Internet Standard, so check out Section 2 of RFC 5741 for the deets 🙈.

If you want the current status, errata, or a way to give feedback, go to http://www.rfc-editor.org/info/rfc7799 🍓.

Copyright Notice ✨

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they stand on the publication date 📜. Please read these carefully, because they spell out your rights and restrictions for this document 💅. Code Components pulled out of this document must include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and come with no warranty, same as the Simplified BSD License says 🔥.

Table of Contents ✨

1. Introduction ....................................................2
   1.1. Requirements Language ......................................3
2. Purpose and Scope ...............................................3
3. Terms and Definitions ...........................................3
   3.1. Performance Metric .........................................3
   3.2. Method of Measurement ......................................4
   3.3. Observation Point ..........................................4
   3.4. Active Methods .............................................4
   3.5. Active Metric ..............................................5
   3.6. Passive Methods ............................................5
   3.7. Passive Metric .............................................6
   3.8. Hybrid Methods and Metrics .................................6
4. Discussion ......................................................8
   4.1. Graphical Representation ...................................8
   4.2. Discussion of PDM .........................................10
   4.3. Discussion of "Coloring" Method ...........................11
   4.4. Brief Discussion of OAM Methods ...........................11
5. Security Considerations ........................................12
6. References .....................................................12
   6.1. Normative References ......................................12
   6.2. Informative References ....................................13
Acknowledgements ..................................................14
Author's Address ..................................................14

1. Introduction 🌸

Okay so the words "Active" and "Passive" have been around for ages to tell apart two different classes of Internet performance assessment 💅. The first Passive and Active Measurement (PAM) Conference happened in 2000, but the oldest proceedings you can find online are from the second PAM conference in 2001 <https://www.ripe.net/ripe/meetings/pam-2001> 🦋.

The notions of "Active" and "Passive" are super well-established 👑. Generally speaking:

An Active Metric or Method depends on a dedicated measurement packet stream and on observations of that stream 🎀.
A Passive Metric or Method depends solely on observation of one or more existing packet streams 💜. Those streams only serve measurement when someone observes them for that purpose, and they're there whether or not any measuring happens 🫶.

As new techniques show up, it's so helpful to have clear definitions of these ideas 🔥. This memo gives more detailed definitions, sets up a new category for combos of traditional Active and Passive techniques, and talks about dimensions for evaluating new techniques as they emerge ✨.

This memo defines Active and Passive Metrics and Methods based on long usage in the Internet measurement community, especially the Internet Engineering Task Force (IETF) 🌈. It also covers the mix of fundamental Active and Passive categories called Hybrid Methods and Metrics 🧚.

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 [RFC2119] 📜.

2. Purpose and Scope 🎀

The whole point of this memo is to define and describe Active and Passive versions of metrics and methods that match how these adjectives have been used for a long time in the Internet measurement community, especially the IETF 💅. Measurement science keeps growing, so we add a category for combinations of the traditional extremes 🦋. We treat Active and Passive as a continuum, and we call combinations of their attributes Hybrid Methods 🌸.

This memo also describes multiple dimensions for evaluating new methods as they emerge 💜.

3. Terms and Definitions 🍓

This section defines the key terms of the memo 🔥. Some definitions use the idea of a "stream of interest," which is the same thing as the "population of interest" defined in clause 6.1.1 of ITU-T Recommendation Y.1540 [Y.1540] 👑. These definitions will be handy for any work in progress, like [PASSIVE], which is already pretty consistent with them 🫶.

3.1. Performance Metric ✨

This is the standard definition of a quantity, produced when you assess the performance and/or reliability of the network 💖. It has an intended utility and is carefully specified so it conveys the exact meaning of a measured value 🌈. (This matches the definition of Performance Metric in [RFC2330] and [RFC6390] 💅.)

3.2. Method of Measurement ✨

This is the procedure or set of operations whose goal is determining a Measured Value or Measurement Result 🎀.

3.3. Observation Point ✨

Check out Section 2 of [RFC7011] for the definition of Observation Point (a location in the network where packets can be observed), plus related definitions 🦋. The comparable term in IETF literature on Active measurement is "Measurement Point" (see Section 4.1 of [RFC5835]) 🧚. Both terms have caught on for describing similar things at the identified point in the network path 💜.

3.4. Active Methods ✨

Active Methods of Measurement have these attributes 🔥:

Active Methods generate packet streams 💅. Usually, the packet stream of interest is generated as the basis of measurement 🌸. Sometimes people use the word "synthetic" to describe Active measurement streams [Y.1731] 🦋. An accompanying packet stream (or streams) may be generated to increase overall traffic load, though the loading stream(s) may not be measured 🫶.
The packets in the stream of interest have fields or field values (or get augmented or modified to include fields or field values) that are dedicated to measurement 💖. Since measurement usually means finding the matching packets at multiple measurement points, a sequence number is the most common info dedicated to measurement, and it's often paired with a timestamp ⭐.
The Source and Destination of the packet stream of interest are usually known a priori 👑.
The characteristics of the packet stream of interest are known at the Source (at least), and can be communicated to the Destination as part of the method 🌈. Heads up: some packet characteristics normally change during packet forwarding 🙈. Other changes along the path are possible, see [STDFORM] 🍓.

When Active Methods add traffic to the network for measurement, they influence the quantities measured to some degree 💀. Anyone running tests should take steps to quantify those effects and/or minimize them 🫶.

3.5. Active Metric ✨

An Active Metric bakes one or more of the aspects of Active Methods into the metric definition 💜.

For example, IETF metrics for IP performance (developed under the framework described in [RFC2330]) include the Source-packet stream characteristics as metric-input parameters 🦋. They also specify the packet characteristics (Type-P) and the Source and Destination IP addresses, with their implications on both stream treatment and the interfaces tied to measurement points 🎀.

3.6. Passive Methods ✨

Passive Methods of Measurement are 💅:

based solely on observations of an undisturbed and unmodified packet stream of interest. In other words, the method of measurement MUST NOT add, change, or remove packets or fields, or change field values anywhere along the path 🔥.
dependent on the existence of one or more packet streams to supply the stream of interest 🌸.
dependent on the presence of the packet stream of interest at one or more designated Observation Points 🦋.

Some Passive Methods just observe and collect info on all packets that pass the Observation Point(s) 🌈. Others filter packets first and only collect info on packets matching the filter criteria, which narrows the stream of interest 🧚.

Passive Methods are commonly run at one or more Observation Points 💖. Passive Methods that assess Performance Metrics often need multiple Observation Points, for example to assess the latency of packet transfer across a network path between two Observation Points ⭐. In that case, the observed packets must include enough information to determine the corresponding packets at the different Observation Points 🫶.

Sending the observations (in some form) to a collector is an essential part of Passive Methods 👑. In some setups, the traffic load created when communicating (or exporting) the Passive Method results to a collector may itself influence the performance of the measured network 🙈. But collecting results isn't unique to Passive Methods, so the load from managing and operating measurement systems MUST always be considered for potential effects on the measured values 💀.

Part 1 done, bestie! 🎀💖 Part 2 is coming with the rest of the Passive Methods, the Hybrid stuff, and more 🦋✨

3.7. Passive Metric ✨

okay so Passive Metrics are all about watching packet traffic 👀 (traffic flows in [RFC7011]) 🦋

Passive performance metrics are assessed completely independently of the packets or traffic flows, and only through observation. Some people call this "out of band" 🫶

One example of Passive Performance Metrics for IP packet transfer is in ITU-T Recommendation Y.1540 [Y.1540], where the metrics are defined based on reference events that get generated as packets pass reference points. The metrics don't care about the Active vs Passive distinction when the necessary packet correspondence can be derived from the observed stream of interest as required. 💅

3.8. Hybrid Methods and Metrics 🌈

Hybrid Methods are Methods of Measurement that mix Active Methods and Passive Methods together. They can assess Active Metrics, Passive Metrics, or brand new metrics derived from the a priori knowledge and observations of the stream of interest. ITU-T Recommendation Y.1540 [Y.1540] defines metrics that also work for the hybrid categories, since packet correspondence at different observation/reference points could be derived from "fields or field values which are dedicated to measurement", but otherwise the methods are Passive. 🧚

There are several types of Hybrid Methods, categorized below. 🍓

With respect to a single stream of interest, Hybrid Type I methods fit on the continuum as follows, in terms of what happens at the Source (or Observation Point nearby):

Generation of the stream of interest => Active
Augmentation or modification of the stream of interest, or employment of methods that modify the treatment of the stream => Hybrid Type I
Observation of a stream of interest => Passive

As an example, consider the case where the method generates traffic load stream(s), and observes an existing stream of interest according to the criteria for Passive Methods. Since loading streams are an aspect of Active Methods, the stream of interest is not "solely observed", and the measurements involve a single stream of interest whose treatment has been modified by the presence of the load. Therefore, this is a Hybrid Type I method. 😭

We define Hybrid Type II as follows: Methods that employ two or more different streams of interest with some degree of mutual coordination (e.g., one or more Active streams and one or more undisturbed and unmodified packet streams) to collect both Active and Passive Metrics and enable enhanced characterization from additional joint analysis. [HYBRID] presents a problem statement for Hybrid Type II Methods and Metrics. Note that one or more Hybrid Type I streams could be substituted for the Active streams or undisturbed streams in the mutually coordinated set. It is the Type II Methods where unique Hybrid Metrics are anticipated to emerge. 🔥

Methods based on a combination of a single (generated) Active stream and Passive observations applied to the stream of interest at intermediate Observation Points are also Hybrid Methods. However, [RFC5644] already defines these as Spatial Metrics and Methods. It is possible to replace the Active stream of [RFC5644] with a Hybrid Type I stream and measure Spatial Metrics (but this was unanticipated when [RFC5644] was developed). 👑

The table below illustrates the categorization of methods (where "Synthesis" refers to a combination of Active and Passive Method attributes). 📊

                   | Single Stream          | Multiple Simultaneous
                   | of Interest            | Streams of Interest
                   |                        | from Different Methods
   ====================================================================
   Single Fundamental  | Active or Passive      |
   Method              |                        |

   Synthesis of        | Hybrid Type I          |
   Fundamental Methods |                        |

   Multiple Methods    | Spatial Metrics        | Hybrid Type II
                       | [RFC5644]              |

There may be circumstances where results measured with Hybrid Methods can be considered equivalent to those measured with Passive Methods. This notion references the possibility of a "class C" where packets of different Type-P are treated equally in network implementation, as described in Section 13 of [RFC2330] and using the terminology for paths from Section 5 of [RFC2330]: 🎀

Hybrid Methods of measurement that augment or modify packets of a "class C" in a host should produce results equivalent to Passive Methods of Measurement when hosts accessing and links transporting these packets along the path (other than those performing augmentation/modification) treat packets from both categories of methods (with and without the augmentation/modification) as the same "class C". The Passive Methods of Measurement represent the Ground Truth when comparing results between Passive and Hybrid Methods, and this comparison should be conducted to confirm the "class C" treatment.

4. Discussion ✨

This section illustrates the definitions and presents some examples. 🌸

4.1. Graphical Representation 📈

If we compare the Active and Passive Methods, there are at least two dimensions on which methods can be evaluated. This evaluation space may be useful when a method is a combination of the two alternative methods. 💖

The two dimensions (initially chosen) are:

Y-Axis: "Effect of the measured stream on network conditions". The degree to which the stream of interest biases overall network conditions experienced by that stream and other streams. This is a key dimension for Active measurement error analysis. (Comment: There is also the notion of time averages -- a measurement stream may have significant effect while it is present, but the stream is only generated 0.1% of the time. On the other hand, observations alone have no effect on network performance. To keep these dimensions simple, we consider the stream effect only when it is present, but note that reactive networks defined in [RFC7312] may exhibit bias for some time beyond the life of a stream.) 🙈

X-Axis: "a priori Stream Knowledge". The degree to which stream characteristics are known a priori. There are methodological advantages of knowing the source stream characteristics, and having complete control of the stream characteristics. For example, knowing the number of packets in a stream allows more-efficient operation of the measurement receiver, and so is an asset for Active Methods of Measurement. Passive Methods (with no sample filter) have few clues available to anticipate what protocol the first packet observed will use or how many packets will comprise the flow; once the standard protocol of a flow is known, the possibilities narrow (for some compliant flows). Therefore, this is a key dimension for Passive measurement error analysis. 🧠

There are a few examples we can plot on a two-dimensional space. We can anchor the dimensions with reference point descriptions. 🗺️

Y-Axis:Effect of the measured stream on network conditions
^ Max
|* Active using max capacity stream
|
|
|
|
|* Active using stream with load of typical user
|
|
|
|* Active using extremely sparse, randomized stream
|                             * PDM                        Passive
| Min                                                            *
+----------------------------------------------------------------|
|                                                                |
Stream          X-Axis: a priori Stream Knowledge        No Stream
Characteristics                                    Characteristics
Completely                                                   Known
Known

(In the graph above, "PDM" refers to [PDMOPTION], an IPv6 Option Header for Performance and Diagnostic Measurements, described in Section 4.2.)

We recognize that method categorization could be based on additional dimensions, but this would require a different graphical approach. 🌈

For example, "effect of stream of interest on network conditions" could easily be further qualified into:

effect on the performance of the stream of interest itself: for example, choosing a packet marking or Differentiated Services Code Point (DSCP) resulting in domain treatment as a real-time stream (as opposed to default/best-effort marking).
effect on unmeasured streams that share the path and/or bottlenecks: for example, an extremely sparse measured stream of minimal size packets typically has little effect on other flows (and itself), while a stream designed to characterize path capacity may affect all other flows passing through the capacity bottleneck (including itself).
effect on network conditions resulting in network adaptation: for example, a network monitoring load and congestion conditions might change routing, placing some flows on alternate paths to mitigate the congestion.

We have combined 1 and 2 on the Y-axis, as examination of examples indicates strong correlation of the effects in this pair, and network adaptation is not addressed. 🦋

It is apparent that different methods of IP network measurement can produce different results, even when measuring the same path at the same time. The two dimensions of the graph help us to understand how the results might change with the method chosen. For example, an Active Method to assess throughput adds some amount of traffic to the network, which might result in lower throughput for all streams. However, a Passive Method to assess throughput can also err on the low side due to unknown limitations of the hosts providing traffic, competition for host resources, limitations of the network interface, or private sub-networks that are not an intentional part of the path, etc. Hybrid Methods could easily suffer from both forms of error. Another example of potential errors stems from the pitfalls of using an Active stream with known a bias, such as a periodic stream defined in [RFC3432]. The strength of modeling periodic streams (like Voice over IP (VoIP)) is a potential weakness when extending the measured results to other application whose streams are non-periodic. The solutions are to model the application streams more exactly with an Active Method or to accept the risks and potential errors with the Passive Method discussed above. 😤

4.2. Discussion of PDM 🎧

In [PDMOPTION], an IPv6 Option Header for Performance and Diagnostic Measurements (PDM) is described which, when added to the stream of interest at strategic interfaces, supports performance measurements. This method processes a user traffic stream and adds "fields which are dedicated to measurement" (the measurement intent is made clear in the title of this option). Thus:

The method intends to have a minor effect on the measured stream and other streams in the network. There are conditions where this intent may not be realized.
The measured stream has unknown characteristics until it is processed to add the PDM Option header. Note that if the packet MTU is exceeded after adding the header, the intent to have a minor effect will not be realized.

We conclude that this is a Hybrid Type I method, having at least one characteristic of both Active and Passive Methods for a single stream of interest. 💜

4.3. Discussion of "Coloring" Method ✨

okay so [OPSAWG] 🌸 proposed to color packets by re-writing a field of the stream at strategic interfaces to support performance measurements. ngl this is a difficult operation at an intermediate point on an encrypted Virtual Private Network 💀. The method processes a user traffic stream and inserts "fields or values which are dedicated to measurement". Here's the tea:

The method intends to have a minor effect on the measured stream and other streams in the network (less than PDM above) 🦋. There are conditions where this intent may not be realized 🙈.
The measured stream has unknown characteristics until it is processed to add the coloring in the header 💅, and the stream could be measured and time-stamped during that process ⏱️.

We note that [COLORING] proposes a method similar to [OPSAWG], as discussion on the IPPM mailing list revealed 💜. Two proposals, same vibe, the group chat noticed 😭.

We conclude that this is a Hybrid Type I method, having at least one characteristic of both Active and Passive Methods for a single stream of interest 👑. It's got a foot in both camps, iconic 🫶.

4.4. Brief Discussion of OAM Methods

Many Operations, Administration, and Management (OAM) methods exist beyond the IP layer 🧚. For example, [Y.1731] defines several different measurement methods that we would classify as follows:

Loss Measurement (LM) occasionally injects frames with a count of previous frames since the last LM message 🍓. We conclude LM is Hybrid Type I, because this method processes a user traffic stream and augments the stream of interest with frames having "fields which are dedicated to measurement" 🎀.
Synthetic Loss Measurement (SLM) and Delay Measurement (DM) methods both inject dedicated measurement frames, so the "stream of interest is generated as the basis of measurement" ✨. We conclude that SLM and DM methods are Active Methods 🔥.

We also recognize the existence of alternate terminology used in OAM at layers other than IP 🌈. Readers are encouraged to consult [RFC6374] for MPLS Loss and Delay measurement terminology, for example 📖.

5. Security Considerations 🔒

Okay, this part is seriously important bestie 😤. When considering the security and privacy of those involved in measurement or those whose traffic is measured, there is sensitive information communicated and observed at observation and measurement points described above, and protocol issues to consider 🚨. We refer the reader to the security and privacy considerations described in the Large-Scale Measurement of Broadband Performance (LMAP) Framework [RFC7594], which covers Active and Passive measurement techniques and supporting material on measurement context 🛡️. Read it, no skipping 💖.

6. References 📚

6.1. Normative References

[RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119,
           DOI 10.17487/RFC2119, March 1997,
           <http://www.rfc-editor.org/info/rfc2119>.

[RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
           "Framework for IP Performance Metrics", RFC 2330,
           DOI 10.17487/RFC2330, May 1998,
           <http://www.rfc-editor.org/info/rfc2330>.

[RFC3432]  Raisanen, V., Grotefeld, G., and A. Morton, "Network
           performance measurement with periodic streams", RFC 3432,
           DOI 10.17487/RFC3432, November 2002,
           <http://www.rfc-editor.org/info/rfc3432>.

[RFC5644]  Stephan, E., Liang, L., and A. Morton, "IP Performance
           Metrics (IPPM): Spatial and Multicast", RFC 5644,
           DOI 10.17487/RFC5644, October 2009,
           <http://www.rfc-editor.org/info/rfc5644>.

[RFC5835]  Morton, A., Ed. and S. Van den Berghe, Ed., "Framework for
           Metric Composition", RFC 5835, DOI 10.17487/RFC5835, April
           2010, <http://www.rfc-editor.org/info/rfc5835>.

[RFC6390]  Clark, A. and B. Claise, "Guidelines for Considering New
           Performance Metric Development", BCP 170, RFC 6390,
           DOI 10.17487/RFC6390, October 2011,
           <http://www.rfc-editor.org/info/rfc6390>.

[RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
           "Specification of the IP Flow Information Export (IPFIX)
           Protocol for the Exchange of Flow Information", STD 77,
           RFC 7011, DOI 10.17487/RFC7011, September 2013,
           <http://www.rfc-editor.org/info/rfc7011>.

[RFC7312]  Fabini, J. and A. Morton, "Advanced Stream and Sampling
           Framework for IP Performance Metrics (IPPM)", RFC 7312,
           DOI 10.17487/RFC7312, August 2014,
           <http://www.rfc-editor.org/info/rfc7312>.

[RFC7594]  Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
           Aitken, P., and A. Akhter, "A Framework for Large-Scale
           Measurement of Broadband Performance (LMAP)", RFC 7594,
           DOI 10.17487/RFC7594, September 2015,
           <http://www.rfc-editor.org/info/rfc7594>.

6.2. Informative References

[COLORING]
           Chen, M., Ed., Zheng, L., Ed., Mirsky, G., Ed., Fioccola,
           G., Ed., and T. Mizrahi, Ed., "IP Flow Performance
           Measurement Framework", Work in Progress,
           draft-chen-ippm-coloring-based-ipfpm-framework-06, March 2016.

[HYBRID]   Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo,
           "Hybrid Measurement using IPPM Metrics", Work in Progress,
           draft-trammell-ippm-hybrid-ps-01, February 2014.

[OPSAWG]   Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda,
           "A packet based method for passive performance
           monitoring", Work in Progress, draft-tempia-opsawg-p3m-04,
           February 2014.

[PASSIVE]  Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G.
           Mirsky, "Framework for IP Passive Performance
           Measurements", Work in Progress, draft-zheng-ippm-
           framework-passive-03, February 2015.

[PDMOPTION]
           Elkins, N. and M. Ackermann, "IPv6 Performance and
           Diagnostic Metrics (PDM) Destination Option", Work in
           Progress, draft-ietf-ippm-6man-pdm-option-02, April 2016.

[RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
           Measurement for MPLS Networks", RFC 6374,
           DOI 10.17487/RFC6374, September 2011,
           <http://www.rfc-editor.org/info/rfc6374>.

[STDFORM]  Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V.
           Hegde, "Updates for IPPM's Active Metric Framework:
           Packets of Type-P and Standard-Formed Packets", Work in
           Progress, draft-morton-ippm-2330-stdform-typep-02,
           December 2015.

[Y.1540]   ITU-T, "Internet protocol data communication service - IP
           packet transfer and availability performance parameters",
           March 2011,
           <https://www.itu.int/rec/T-REC-Y.1540-201103-I/en>.

[Y.1731]   ITU-T, "Operation, administration and management (OAM)
           functions and mechanisms for Ethernet-based networks",
           August 2015,
           <https://www.itu.int/rec/T-REC-G.8013-201508-I/en>.

Acknowledgements 🫶

Huge thanks to Mike Ackermann for asking the right question, and for several suggestions on terminology 👏. Brian Trammell provided key terms and references for the Passive category, and suggested ways to expand the Hybrid description and types 🌟. Phil Eardley suggested some hybrid scenarios for categorization as part of his review 🎀. Tiziano Ionta reviewed the document and suggested the classification for the "coloring" Method of Measurement 🦋. Nalini Elkins identified several areas for clarification following her review 🧠. Bill Jouris, Stenio Fernandes, and Spencer Dawkins suggested several editorial improvements ✍️. Tal Mizrahi, Joachim Fabini, Greg Mirsky, and Mike Ackermann raised many key considerations in their Working Group Last Call (WGLC) reviews, based on their broad measurement experience 💖. The whole squad showed up 👑.

Author's Address 💌

Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ
United States

Email: acmorton@att.com

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