LMAP Working Group                                               L. Deng
INTERNET-DRAFT                                              China Mobile
Intended Status: Informational                                  L. Zheng
Expires: July 13, 2015                                            Huawei
                                                            M, Ackermann
                                                           BCBS Michigan
                                                               G. Mirsky
                                                            Jan 11, 2015

         Use-cases for Passive Measurement in Wireless Networks


   This document presents use-cases for passive IP performance
   measurements in wireless networks.

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   Provisions Relating to IETF Documents
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Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2  Conventions Used in This Document . . . . . . . . . . . . . . .  4
     2.1 Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2 Requirements Language  . . . . . . . . . . . . . . . . . . .  4
   3 Use-cases  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1 Performance Monitoring for Network Planning/Optimization . .  4
     3.2 End-to-end Measurement for Wireless Subscribers  . . . . . .  5
     3.3 Accurate Fault Identification  . . . . . . . . . . . . . . .  6
   4  Security Considerations . . . . . . . . . . . . . . . . . . . .  8
   5  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  8
   6  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     6.1  Normative References  . . . . . . . . . . . . . . . . . . .  9
     6.2 Informative References . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

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1  Introduction

   It is well-accepted that mobile Internet usage is going to increase
   fast in the coming years and replace the traditional voice service as
   the dominant revenue source for mobile operators.  In the meantime,
   fast evolving network and terminal technologies and changing service
   trends (e.g. social networking, video on demand, online reading,
   etc.) result in more stringent user service requirements. Therefore,
   as the basic infrastructure service providers, operators are deemed
   responsible for mobile Internet end-to-end performance because
   subscribers want to get what they want, which gives rise to a basic
   yet important question: how does network service provider manage end-
   to-end Quality of Service (QoS)?  In particular, there are two goals
   for operator's quality management initiative:

   o  to make sure and validate the QoS metrics of specific IP flows
   against the values pre-defined by the service Service Level
   Agreement(SLA) from the perspective of either the subscriber or
    the Internet Content Provider (ICP); and

   o  to make sure and validate the sanity of network devices/links.

   Passive measurements, where observation on existing traffic is the
   only means for measurement entities, have been extensively used in
   scenarios where active measurement alone may not be sufficient to
   characterize performance over a particular service path. For example,
   the active measurement traffic may not be in-band with   the real
   traffic that it is intended to simulate as a result of dynamics in
   routing techniques, e.g. Equal Cost Multi-Path (ECMP) [RFC2991] or
   device pooling[3GPP TS23.236].

   Overall there are many characteristics of injected active test
   traffic that can render behaviors and measured metrics may be
   different from the actual user traffic flows and performance.  Since
   the ultimate goal is understanding the actual user traffic
   performance, measuring the actual (Passive) traffic itself,
   represents an important measurement method to achieve effective and
   accurate results.

   In this draft, we present three use-cases of passive measurements for
   wireless networks, where active IP performance measurements are not
   desirable or accurate enough in achieving the above goals.

   It is worth notice that some of the use-cases are not unique to
   Wireless networks, and can be applied to wired networks as well.

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2  Conventions Used in This Document

2.1 Terminology

   ECMP - Equal Cost Multi-Path

   ISP - Internet Service Provider

   QoE - Quality of Experience

   QoS - Quality of Service

   RAN - Radio Access Network

   SLA - Service Level Agreement

   UE  - User Equipment

   MP - Measurement Point, a node or juncture within an IP Network
   Session Path at which information regarding the performance or
   reliability of the session path is observed, examined or measured.

   Ma - Measurement Agent, the software entity integrated into a
   measurement point that actually does the function of performance
   measurement related tasks.

2.2 Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3 Use-cases

   In light of the introduction of more capable passive measurement
   methods than pure observation in[I.D-zheng-ippm-framework-passive],
   it is expected that passive measurements would be the basic building
   block in performance monitoring in highly dynamic and resource-
   limited production networks like wireless access networks.

   This section presents use-cases for passive measurements in wireless

3.1 Performance Monitoring for Network Planning/Optimization

   As mentioned earlier, it is important for Internet Service Providers

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   (ISPs) to understand their network performance through continuous and
   accurate performance monitoring in terms of the experience of network
   customers in addition to the status of the physical network.

   However, due to the traffic dynamics in terms of its geographic and
   time distribution, accurate monitoring of actual traffic QoS,
   necessary for network planning or adaptive network optimization,
   cannot be achieved by active measurements alone. Because active
   measurement methods measure performance metrics by means of carefully
   designed and injected active measurement traffic, whose
   characteristics may be quite different from those of the real traffic
   in a production network, and not flexible to account for the impact
   from traffic dynamics. Moreover, the injected active traffic could
   even skew results or measurements, rendering the continuous non-
   interfering monitoring of traffic QoS impossible with active
   measurements along. This could be especially problematic when
   associated results are used for performing network planning and
   optimization. E.g. for network planning, it is important to evaluate
   the Quality of Experience (QoE) and network performance during the
   peak hours, when active measurements are least desirable. It is also
   helpful to understand the user experience during non-peak hours in
   order to better assist the application and verify its sophisticated
   dynamic resource provisioning schemes, such as elastic resource

   Alternatively, deploying passive measurement points/agents in the
   wireless network, operators can draw a continuous  graph of the
   network usage and performance metric as the basis of network/resource
   planning. Since interference to network performance introduced by
   data collection of a passive measurement may be viewed as negligent,
   it can be initiated almost any time of the day and applied to rush
   hours as well.

3.2 End-to-end Measurement for Wireless Subscribers

   For wireless networks, almost all the time, the wireless "last mile"
   would be the bottleneck for end-to-end QoS and QoE, indicating the
   necessity to include the wireless segment into the measurement path.

   However, due to the limited availability and/or relatively high cost
   of wireless resources, it is not economic for either ISP or the user
   to conduct resource-demanding active measurements over the wireless

   For instance, unlike the fixed network providers where the access
   network resource is shared by a group of subscribers who are charged
   by the duration of their subscriptions independent of their actual

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   network usage, wireless/mobile ISPs make extensive use of resource
   allocation and reservation for individual terminals/IP flows and
   often use the traffic volume consumption as the basis for
   subscription billing. In other words, the subscriber may be charged
   for the active measurement traffic despite the fact that it degrades
   QoE of real application data transfer during the Active measurement.

   Therefore, measurements pertaining to the performance of Subscribers
   or End Users, are particularly dependent upon passive measurements.
   As stated, Active measurements conducted in this realm can be
   expensive and even affect QoE. Possibly even greater concern is that
   the results of the Active measurements may not match the results of
   the actual End User traffic (for various reasons discussed in Section
   3.1).  The Passive measurements more likely match the results of the
   actual End User traffic, because they are based on the same traffic.

3.3 Accurate Fault Identification

   It is quite common that there are multiple domains (belonging to
   different operational or administrative bodies) along the data path
   from a mobile user equipment (UE) to the Internet.

   Case 1: intermediary ISP: consider the example of a mobile subscriber
   getting access from a 3GPP network. Besides a local mobile network
   operator, intermediary ISPs may exist in between before subscriber's
   traffic reaches the Internet.

   Case2: path partitioning: as shown in Figure 1, within the local
   operator's network, radio access network (RAN), RAN backhaul and
   local core network could actually be constructed and managed by staff
   from different departments.

   Case3: geographic partitioning: for large operators, employing
   layered network operation and management architecture based on
   geographic partitions, there may be a further more subpath
   partitioning between local IP backhaul (managed by state sub-
   ordinaries) and national IP backhaul (managed by headquarters).

               +-|---+           +------+         +------+        +----+
    +--+       |     |  Tunnel1  |      | Tunnel2 |      |  Ext   |    |
    |UE|-(RAN)-| eNB |===========| S-GW |=========| P-GW |--------|SP  |
    +--+       |     |    RAN    |      |  Core   |      |Network |    |
               +-+---+  Backhaul +---+--+ Network +---+--+        +--+-+

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   Figure 1: Example of path partition in 3GPP network

   Case4: roaming partitioning: Moreover, for roaming cases under home-
   routed mode, all the traffic from a roaming UE would first traverse
   from the visited ISP and potentially another Internet operator before
   getting back to homing ISP network.

   In these cross-domain scenarios, in order to do effective trouble
   shooting for degraded QoS, one needs to first identify the faulty
   domain or cross-domain interconnection from well performing domains,
   and then further drill down for the overloaded device/link within the
   identified domain. If Active measurements are employed, cross-
   boundary traffic and cross-provider coordination on the
   interconnections may be required to complicate the process.

   On the contrary, passive measurements can help in accurate trouble-
   shooting and problem demarcation between various networking
   technologies or operational domains that together compose an end-to-
   end traffic path, since it does not require extra cross-boundary
   traffic to be injected into the path or strict synchronization to be
   conducted between participating measurement points/agents as Active
   measurements do.

   Passive measurements can be used both for the end-to-end problem
   identification and the hop-by-hop demarcation. By deploying
   measurement points/agents both within the domains and at the cross-
   boundary interconnections, passive measurements can quickly identify
   the faulty domain/device/link without introducing extra cross-
   boundary measurement traffic.

   For instance, Passive measurement points/agents can be deployed at
   both the ingress and the egress point of each domain and work
   independently along the path for the passive performance measurement.
   A simple aggregation at a third-party data collector can do the
   drilling measurement result analysis to identify the problematic

   More importantly, in the above cross-domain cases, timely fault
   isolation is critical. Alerts/alarms and other indications of
   potential faults may be provided more quickly by monitoring and
   measuring on data traffic. As alluded to in the previous paragraphs,
   active monitoring may require significant set up and coordination.
   By the time this occurs, it is conceivable that network conditions,
   may have changed. It is also conceivable that the difference in
   traffic characteristics between the actual traffic, and active
   traffic injected into the network, (no matter how slight the
   differences), may not experience the same issues or faults.

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4  Security Considerations


5  IANA Considerations

   There is no IANA action in this document.

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6  References

6.1  Normative References

6.2 Informative References

   [I.D-zheng-ippm-framework-passive] L. Zheng et al. "Framework for IP
              Passive Measurements", draft-zheng-ippm-framework-passive-
              00(work in progress), June 2014.

   [ECMP] D. Thaler et al. "Multipath Issues in Unicast and Multicast
              Next-Hop Selection", RFC 2991, November 2000.

   [3GPP TS23.236] 3GPP TS 23.236: "Intra Domain Connection of RAN Nodes
              to Multiple CN Nodes", Release 5, November 2004.

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Authors' Addresses

   Lingli Deng
   China Mobile

   Email: denglingli@chinamobile.com

   Lianshu Zheng
   Huawei Technologies

   Email: vero.zheng@huawei.com

   Michael Ackermann
   Blue Cross Blue Shield of Michigan

   Email: mike.ackermann@bcbsmi.com

   Greg Mirsky

   Email: gregory.mirsky@ericsson.com

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