Internet DRAFT - draft-deng-ippm-wireless

draft-deng-ippm-wireless







IPPM                                                             L. Deng
Internet-Draft                                                    Z. Cao
Intended status: Informational                              China Mobile
Expires: August 16, 2014                               February 12, 2014


        Problem Statement for IP measurement in mobile networks
                    draft-deng-ippm-wireless-01.txt

Abstract

   This document analyzes the potential problems of applying existing
   IP-based performance measurement methods to wireless accessing
   environments.  It suggests that a more flexible passive measuring
   framework and performance metrics, such as congestion ratio are
   needed.

Status of This Memo

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   This Internet-Draft will expire on August 16, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Dynamic Load Balancing  . . . . . . . . . . . . . . . . .   3
     2.2.  Radio Congestion Detection  . . . . . . . . . . . . . . .   4
     2.3.  Accurate Troubleshooting  . . . . . . . . . . . . . . . .   5
     2.4.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Further Considerations  . . . . . . . . . . . . . . . . . . .   7
     3.1.  Congestion ratio metric . . . . . . . . . . . . . . . . .   7
     3.2.  Multi-hop Measurement Framework . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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 to
   be the dominant revenue source for mobile operators.  In the
   meantime, fast evolving network and terminal technologies and
   changing service trend (e.g. social networking, video on demand,
   online reading, etc.) results in higher user service requirement.
   Therefore, as the basic infrastructure service provider, operators are
   deemed responsible for mobile Internet end-to-end performance, for
   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 service quality?  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 SLA(Service Level
      Agreement) from the user/service provider's point of view; and
   o  to make sure and validate the sanity of network devices/links.

   In this draft, we present three usecases and the potential problems
   of applying existing IP-based performance measurement methods to
   wireless accessing environments, where resource pooling and dynamic
   load balancing techniques are employed to accommodate explosively
   increasing data traffic, and suggest requirements for more robust
   passive measuring methods and performance metrics for such
   environment.






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2.  Motivation

2.1.  Dynamic Load Balancing

   Pooling technology has been introduced to the user plane in the
   packet switched domain of operator's core network for cellular
   subscribers since 3GPP Release 5 (3GPP TS23.236).  With pooling, the
   traffic path from user equipments to the Internet via core network
   is not static, but rather dynamically assigned to a proper instance
   of an device pool, according to load balancing policies.  The
   assignment is dynamically made at the time of user equipment's
   attachment establishment with the cellular core network, and would
   remain unchanged unless the mobile terminal detaches from the network
   or moves outside the base-stations' coverage subordinating to the
   specific core network's device pool.

   As shown by Figure 1, potential device pools along the path all the
   way from the user terminal via the packet switching domain of the
   mobile network core to a third party service provider over the
   Internet.  Examples of network devices that can be poolized
   include SGSN(Serving GPRS Support Node) and GGSN(Gateway GPRS
   Supporting Node).  Moreover, the service provider could also
   implement load balancing on the server's side either via server-
   pooling within a data center or via (third party) CDN nodes.



























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Radio       |Packet                                   |Internet
Access      |Switching                                |
Network     |Core Network                             |
            |                   +--------+       +----+---+       +--------+
            |                   |+------+|       |+------+|       |+------+|
            |                +-->|SGSN_1|+------->|GGSN_1|+--+    ||SERV_1||
            |                |  |+------+|       |+------+|  |    |+------+|
+--+     +--+--+    +-----+  |  |        |       |        |  |    |        |
|  |---->|     +--->|     +--+  |+------+|       |+------+|  |    |+------+|
|UE|     |NodeB|    | RNC |     ||SGSN_2||       ||GGSN_2||  +---->|SERV_2||
|  |....>|     |...>|     |...  |+------+|       |+------+|       |+------+|
+--+     +--+--+    +-----+  .  |        |       |        |       |        |
            |                .  |   ...  |       |  ...   |       |   ...  |
            |                .  |+------+|       |+------+|       |+------+|
  +--------------------+     ...>|SGSN_N|........>|GGSN_M|........>|SERV_K||
  |  Injected Traffic  |        |+------+|       |+------+|       |+------+|
  |  --------------->  |        +--------+       +----+---+       +--------+
  |   Actual Traffic   |                              |
  |  ...............>  |                              |
  +--------------------+


    Figure 1: Active Measuring Traffic versus Actual Traffic in case of
                              Device Pooling

   Hence, under such environments, if active performance measurement
   methods[RFC4656][RFC5357] are employed, the injected bogus data
   traffic may traverse along a different path to the one used by the
   targeted traffic or even interfere with them due to the subtle nature
   of wireless-involved links (as explained in the next subsection).

2.2.  Radio Congestion Detection

   Mobile Internet usage is going to increase fast in the coming years
   due to the following facts: on one hand, as a result of pervasively
   deployed and fast maturing 3G/4G cellular technologies combined with
   smartphone's dominance in mobile handset's market, Internet data
   traffic via mobile operator's packet switched core network manifests
   to be an increasingly important contributor to the operator's
   revenue.  On the other hand, wireless technologies (such as Wi-Fi
   through APs or cellular networks through small cells) are more and
   more accepted by the end users, either at home, in the office or in a
   public place, to be carrying the "last mile" to various portable
   personal computing devices.

   There are two common features of the above two scenarios:





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   o  the combination of both wireless and wired links along the end-to-
      end traffic path, and
   o  almost all the time, the wireless "last mile" would be the
      bottleneck of end-to-end service quality.

   To make more efficient use of relatively more scarce radio resources,
   it is important for the core network to understand the congestion
   status of both wireless and wired links along the traffic path, and
   make proper management of data traffic through cell reselection or
   load balancing via pooling.

   However, the wireless link's thoughput is consistently subject to
   other interfering factors (e.g. distance to the nearest base
   station, terminal's radio signal strength, random interference,
   shadowing of buildings, multipath fading, etc.), which should be
   properly filtered out before handing over to the network management,
   as they are rooted in terminal mobility and outside the realm of
   mobile accessing network.

   In other words, there is considerable gap between IP measurement
   results to the performance evaluation and fault detection
   requirements in mobile-involved environment, if we directly employ
   existing passive performance measurement
   methods[I-D.draft-chen-ippm-coloring-based-ipfpm-framework].

2.3.  Accurate Troubleshooting

   As shown in Figure 2, it is quite common that there are path
   partitions (belonging to different operation and management
   departments) along the local data path from the UE to the Internet
   within an mobile operator's local network.  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 header quarters).
   Moreover, for roaming cases under home-routed mode (meaning 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.

   Take the example of a mobile subscriber getting access from a 3GPP
   network for example, besides a local mobile network operator,
   intermediary ISPs may exist between its traffic before it 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 stuff from different
   departments, for they mainly come from different technical
   background.



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   In such complex situations, it can become frustrating to respond
   quickly to a simple UoE complaint, due to the exponentially exploded
   complexity to accurately locate the potential faults/congestion in a
   transient wireless-involved end2end data path.

   On the other hand, tunnels, including GRE [RFC2784], GTP [TS29.060],
   IP-in-IP [RFC2003] or IPSec [RFC4301] etc, are widely deployed in
   3GPP networks.  And in 3GPP network tunnels are used to carry end
   user flows within the backhaul network.  Tunnels brings another
   complexity in realizing effective troubleshooting using end2end
   passive methods.


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



            Figure 2: Example of path partition in 3GPP network

   In other words, a flexible passive measurement framework, capable of
   dynamic troubleshooting for partitioned data link, even in case of
   tunnels or autonomous entities is highly valuable.  However, neither
   current active measurement framework as used by OWAMP[RFC4656]/
   TWAMP[RFC5357], nor the passive framework proposed in
   [I-D.draft-chen-ippm-coloring-based-ipfpm-framework] could fit in
   such case.

2.4.  Summary

   In summary, for mobile-ended data paths, we believe there is need for

   o  viable passive measurement framework for active measurements
      inject extra traffic, which may traverse along a different path to
      the one used by the targeted traffic or even interfere with them.
   o  robust metric against transient wireless conditions, as there is
      considerable gap between existing IP measurement metrics (e.g.
      delay, jitter, throughput etc.), which are subject to change
      caused by external environmental factors and of little use to
      operator's traffic management from the network side.





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   o  flexible and trustworthy measurement mechanisms for accurate
      performance monitory and troubleshooting from multi-hop data link
      across operation boundaries.

3.  Further Considerations

3.1.  Congestion ratio metric

   ECN signal for congestion measurement are signalled at IP header by
   intermediary devices before actual congestion occurs, which is
   expected to be an effective indicator to potential QoE degradation,
   irrespective to traffic pattern/wireless conditions.

   [I-D.draft-hedin-ippm-type-p-monitor] proposes to echo ECN-flags into
   TWAMP-test feedback for active measurement.  While, packet-level
   echoing is not viable in passive framework, it is also suspected that
   more meaningful aggregated information (such as congestion extent,
   defined as the ratio of marked packets versus all packets from a
   given IP flow) would be preferred.

3.2.  Multi-hop Measurement Framework

   In current active measurement framework, there is only two entities
   on the data path, the sender and the reflector.  Hence it is not
   straightforward how to apply this framework to an integral multi-hop
   passive measurement case.

   On the other hand, the centralized multi-hop passive framework
   proposed in [I-D.draft-chen-ippm-coloring-based-ipfpm-framework]
   could encounter problems when there is no prior knowledge about or
   control over different partitions along the overall data path.  In
   other words, path discovery mechanism is needed to identify potential
   measurement nodes along the way during/before the actual passive
   measurement.

4.  Security Considerations

   If measurements nodes from different operational domains are used,
   proper device authentication and report authenticity protection
   mechanisms should also be considered in a complete interworking-
   capable solution.

5.  IANA Considerations

   None.






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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.

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

6.2.  Informative References

   [I-D.draft-chen-ippm-coloring-based-ipfpm-framework]
              Chen, M., Liu, H., Yin, Y., Papneja, R., Abhyankar, S.,
              and G. Deng, "Coloring based IP Flow Performance
              Measurement Framework", draft-chen-ippm-coloring-based-
              ipfpm-framework-01 (work in progress), October 2013.

   [I-D.draft-hedin-ippm-type-p-monitor]
              Hedin, J., Mirsky, G., and S. Baillargeon, "Differentiated
              Service Code Point and Explicit Congestion Notification
              Monitoring in Two-Way Active Measurement Protocol
              (TWAMP)", draft-hedin-ippm-type-p-monitor-02 (work in
              progress), October 2013.

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, September 2006.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, October 2008.

Authors' Addresses

   Lingli Deng
   China Mobile

   Email: denglingli@chinamobile.com


   Zhen Cao
   China Mobile

   Email: caozhen@chinamobile.com






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