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
Ericsson
July 2, 2014
Use-cases for Passive Measurement in Wireless Networks
draft-deng-ippm-passive-wireless-usecase-00
Abstract
This document presents use-cases for passive IP performance
measurements in wireless networks.
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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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
networks.
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
departments.
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
TBA.
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
China
Email: denglingli@chinamobile.com
Lianshu Zheng
Huawei Technologies
China
Email: vero.zheng@huawei.com
Michael Ackermann
Blue Cross Blue Shield of Michigan
USA
Email: mike.ackermann@bcbsmi.com
Greg Mirsky
Ericsson
USA
Email: gregory.mirsky@ericsson.com
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