LMAP Working Group                                               L. Deng
INTERNET-DRAFT                                              China Mobile
Intended Status: Informational                                  L. Zheng
Expires: Feburary 3, 2015                                         Huawei
                                                            M, Ackermann
                                                           BCBS Michigan
                                                               G. Mirsky
                                                            July 2, 2014

         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 . . . . . . . . . . . . . . .  3
     2.1 Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  3
     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 . . . . . . . . . . . . . . . . . . . .  7
   5  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  7
   6  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     6.1  Normative References  . . . . . . . . . . . . . . . . . . .  8
     6.2 Informative References . . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9

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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.

2  Conventions Used in This Document

2.1 Terminology

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   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

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
   (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.

   Especially for network planning, it is important to evaluate the
   Quality of Experience (QoE) and network performance during the peak
   hours, where active measurements are not desirable. It is also
   desirable to understand the user experience in non-peak hours, to
   better assist the application and verify of sophisticated dynamic
   resource provisioning schemes, such as elastic resource pooling.

   Due to the traffic dynamics in terms of its geographic and time
   distribution, continuous monitoring of QoS, necessary for adaptive

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   network optimization, cannot be achieved by active measurements
   alone. Because active measurement methods measures 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. The
   injected active traffic could even skew results or measurements. This
   could be especially problematic when associated results are used for
   performing network planning & optimization.

   On the contrary, by deploying passive measurement points in the
   wireless network, it is possible for the ISP to draw a continuous
   graph of the network usage and performance metric as the basis of
   network/resource planning. Since no interference to network
   performance is introduced by traffic injection for a passive
   measurement, it can be initiated almost any time of the day and
   applies 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 of 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
   "last mile".

   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
   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 a basis for subscription
   billing. In other words, the subscriber may be charged for the active
   measurement traffic in despite the fact that it degrades QoE of real
   application data transfer during the active test.

   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 earlier).  The
   Passive measurements more likely match the results of the actual End
   User traffic, because they are based on the same traffic.

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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.

   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.  Moreover, 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

   As shown in Figure 1, 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 +---+--+        +--+-+

   Figure 1: Example of path partition in 3GPP network

   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 methods 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-

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   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 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 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 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 flow.

   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.

4  Security Considerations


5  IANA Considerations

   There is no IANA action in this document.

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6  References

6.1  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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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