IP SLA Video Operation Across Platforms
IP SLA Video Operation Across Platforms
IP SLA Video Operation Across Platforms
Leveraging Cisco IOS to create synthetic traffic to simulate applications, referred to as application probes.
These probes are created using Cisco routers and switches.
Actively monitoring these probes and deriving end-to-end metrics like round-trip time, packet loss, jitter
and one-way delay
Help network administrators to identify baselines from different points in the network, and determine if
these baselines are violated
IP SLA Video Operation (VO) is a new type of IP SLA probe that generates video traffic with the intention of
stressing the network with the same traffic characteristics as a real video endpoint/application would. IP SLA VO is
a Cisco Medianet Media Monitoring technology that enables synthetic traffic generation and monitoring using Cisco
routers and switches. Together with other medianet technologies like Performance Monitor and Mediatrace, IP SLA
VO can be used for:
Troubleshooting application performance both from an end-to-end as well as from a per-hop perspective
Understand the effect of additional video traffic on a production network as well as competing forms of
traffic
Supported Platforms
IP SLA VO is available on platforms listed in Table 1. The table also lists hardware, license and Cisco IOS image
specifications for each platform.
IP SLA VO, similar to other IP SLA probes, has a sender (source) to generate synthetic traffic, and a responder
(destination) to absorb and analyze these packets. Since IP SLA VO generates video traffic at a higher rate than
normal IP SLA traffic, there can be special hardware requirements at the sender. Also, in the case of IP SLA VO,
the responder does not reflect back the video packets to the sender. In this regard, IP SLA VO is unidirectional.
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Table 1. Supported Platforms for IP SLA VO
IP SLA VO Profiles
An IP SLA VO profile describes the traffic characteristics of a particular video application; for instance, distribution
of packet sizes, burstiness, bit rate, packet rate among others. IP SLA VO profiles are available as:
Pre-packaged
Custom
o User-generated using profile generator tool (Catalyst 3K) or using CLI/MIB to configure video
traffic parameters (ISR G2)
Table 2 lists various built-in IP SLA VO profiles available across platforms. As video encoding technology
advances, it is also reflected in how IP SLA VO simulates such traffic. For instance, ISR G2 series are modeled
after the latest TelePresence and IP Video Surveillance Camera (IPVSC) Codecs. Work is underway to implement
the same on Catalyst 3K and Catalyst 4K switches.
!=using custom
profile
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Table 3 lists the pre-packaged profiles available in each platform and their characteristics. The table lists
characteristics like bit rate, resolution, frames per second etc, associated with each profile. Presently, custom
profile is supported on Catalyst 3K and ISR G2 series, and is not available on the Catalyst 4K switches.
IPTV IPTV
BW=2.6 Mbps
IPTV IPTV
BW=2.3 Mbps
CTS-1080P-Best TelePresence
BW=4Mbps, Resolution = 1080P,
Frames/Second = 30
CTS-1080P-Better TelePresence
BW=3.5Mbps, Resolution = 1080P,
Frames/Second = 30
CTS-1080P-Good TelePresence
BW=3Mbps, Resolution = 1080P,
Frames/Second = 30
CTS-720P-Best TelePresence
BW=2.2Mbps, Resolution = 720P,
Frames/Second = 30
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CTS-720P-Better TelePresence
BW=1.5Mbps, Resolution = 720P,
Frames/Second = 30
CTS-720P-Good TelePresence
BW=1Mbps, Resolution = 720P,
Frames/Second = 30
CTS-720P-Lite TelePresence
BW=936Kbps, Resolution = 720P,
Frames/Second = 30
The following provisions have been made to support generation of custom video applications via IP SLA VO:
For ISR G2 routers, CLI/MIB available to configure traffic parameters for a custom video endpoint
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Custom Profile Incorporation in Catalyst 3K switches
The Cisco IP SLA Video Operations Profile Generator Tool, a custom profile generator tool for use with the IP SLA
VO capabilities, is available. The custom profile generated with this tool can be used with Catalyst 3K switches.
This tool is supported on Windows XP/Vista/7 (32/64 bit) operating systems.
The tool and installation instructions can be downloaded from the “Design” tab on the Cisco Medianet Knowledge
Base Portal at the following URL:
http://www.cisco.com/web/solutions/medianet/knowledgebase/index.html
The steps to generate an IP SLA VO profile file for Catalyst 3K switches are:
Step 1. Install the profile generator tool. Currently, the tool is supported only on Windows platforms.
Step 2. The input to the tool is a packet capture file (.pcap). The packet capture needs to have at least 30
seconds worth of traffic for the tool to analyze and generate a traffic profile.
Step 3. Upload the generated profile file to the flash of the switch.
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Custom Profile Incorporation in ISR G2
On the ISR G2 platform, generation of custom IP SLA VO traffic involves configuring profile parameters using the
CLI or using SNMP MIBs. A custom profile can be created, modified, and removed by either CLI or MIB. Each
custom profile has a few mandatory parameters to configure, and depending on the configured endpoint type, it
may have optional parameters to configure but with default values if not configured.
To configure the mandatory parameters for a custom profile, it requires a basic understanding of the target video
traffic characteristics, such as the endpoint type, maximum bit rate and video frame rate. Advanced users with
deeper understanding of video encoding technologies may choose to configure the optional parameters for a
custom profile with higher accuracy in synthetic traffic generation. Some mandatory parameters and all optional
parameters have default values if not configured by the user.
Table 5. Mandatory and Optional Parameters for Custom Profile Generation in ISR G2 Platform
The process of invoking the configured profile in a IP SLA VO session is similar to the Catalyst 3K platform listed in
Configlet 1.
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Table 6. Parameters to Simulate IPVSC traffic on ISR G2 platform
Custom Resolution Typical Averaging Bit rate I-frame I-frame RTP Encoder Content
Profile to frame rate window (kbps) max size refresh average buffer
Name Configure (fps) size (kilobytes) interval size (total control
in IP SLA (ms) (seconds) packet,
VO bytes)
WebEx Resolution Typical Averaging Bit rate I-frame I-frame RTP Encoder Content
Profile to frame rate window (kbps) max size refresh average buffer
Name Configure (fps) size (kilobytes) interval size (total control
in IP SLA (ms) (seconds) packet,
VO bytes)
Configlet 2 in Figure 3 shows the Cisco IOS CLI version of Table 6 to simulate traffic generated by a Cisco 4000
series HD camera.
Figure 3. Configlet 2: Parameters to Simulate Cisco 4000 Series HD Camera on ISR G2 platform
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Table 8. Interoperability Matrix
Cisco Catalyst 3K
12.2(58)SE2
Sender
Cisco Catalyst 4K
15.1(1)G
Sender
Cisco ISR G2
15.2(2)T
Sender
In all current implementations of the IP SLA VO responder, the received packets are process switched and handled
by the CPU. The CPU utilization on the responder side is the determining factor for IP SLA VO deployment, as the
scale values supported on the responder side are lower than on the sender side.
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There are some scaling issues with respect to interoperability between the three platforms which are listed in
Appendix A. The scaling numbers above have to be adhered to both from the sender’s and responder’s
perspective to avoid the issues in Appendix A.
On the Sender
Step 2. Choose the video probe, specify the 4-tuple and the profile type.
On the Responder
#Specify VO probe, source IP, source port, destination IP, destination port and
#Profile type
video 10.10.1.4 2001 source-ip 10.10.1.5 source-port 3001 profile TELEPRESENCE
By default, the IP SLA VO probe has a duration of 20 seconds and a frequency of 15 minutes. This means that the
synthetic traffic is generated for 20 seconds every 15 minutes. This can be adjusted based on the user
requirements using the “duration” and “frequency” command.
The basic configuration remains the same for all platforms. However there are some differences between the two
switch platforms and ISR G2:
1. On the ISR G2 platform, the PVDM3 DSP is used for packet generation. DSP resources have to be allocated
for video (such as IP SLA VO) using the following commands:
voice-card 0
voice-service dsp-reservation <percentage>
#The above is for voice while the remaining DSP resources will be used for Video
2. For individual IP SLA VO probes, DSP resources can be reserved either dynamically or statically. If statically
configured, DSP resources are assured for the entire duration of the probe spanning multiple repetitions. If
reserved dynamically, the DSP resources are reserved for each repetition at best effort. Thus, it is better to
statically allocate a DSP as shown below.
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Figure 6. Configlet 6: Reserving DSP for an IP SLA VO Probe in ISR G2 Platform
ip sla 2
video 10.10.1.4 2001 source-ip 10.10.1.5 source-port 3002 profile TELEPRESENCE
reserve dsp
3. ISR G2 supports emulation of endpoints when the IP SLA VO stream is generated. So the packets in the
synthetic stream have the emulated address and port as the source IP address and the source port number.
The emulated input interface is to specify the ISR G2 network interface from which this synthetic video traffic
comes in by simulation. This setting can be critical if the ISR G2 as the edge router has some policy
configurations for traffic engineering and/or the WAN interface uses IPsec or tunnels. The emulated input
interface are typically configured to be the LAN interface that would connect the emulated video endpoint.
ip sla 6
video 10.27.9.1 3333 source-ip 10.27.1.5 source-port 4444 profile IPVSC
emulate source 172.16.14.10 9999 GigabitEthernet0/1
IP SLA VO Statistics
Configlet 8 shows the end-to-end over the top statistics gathered on the synthetic traffic generated by IP SLA VO.
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Accuracy of IP SLA VO traffic
To determine the similarity of generated traffic to actual traffic, a comparison is made using mathematical and
empirical methods. Mathematical functions like autocorrelation function (ACF)[13] of the packet size and packet
interval along with generated bandwidth is used as a yard-stick to determine how close the synthetic traffic is to the
real traffic.
This analysis is reported in Figure 2-4 for ISR G2 platform. The two curves in the graph are (1) Actual traffic from
the video endpoint (2) Synthetic traffic generated by the platform. The endpoint is a Cisco CTS system generating
traffic at 1080P resolution.
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Figure 10. Auto Correlation Function of Packet Size for ISR G2
Figure 11. Statistical Comparison of Actual vs. Synthetic Traffic for ISR G2
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A similar comparison is made in Figures 5-7 between synthetic traffic generated for IPVSC profile by Catalyst 3K
and the real traffic generated by a Cisco IPVSC endpoint.
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Figure 13. Auto Correlation Function of Packet Size for Catalyst 3K
In conclusion, there are minor differences, however the synthetic traffic representation is fairly accurate in stressing
the network in a similar way to the real video application.
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Performance Monitor and Mediatrace with IP SLA VO
Synthetic traffic generated by IP SLA VO is very similar to real traffic. During pre-deployment assessment using IP
SLA VO, problems can be isolated by using IP SLA VO with other Medianet technologies.
Performance Monitor
o Provides per-flow, per-hop visibility into flow metrics such as packet loss and network jitter for
audio and video streams, and packet loss events and round-trip times (RTT) for data streams.
Mediatrace
IP SLA VO
Performance Monitor and Mediatrace can be invoked on IP SLA VO synthetic steams. There are two avenues to
collect metrics on IP SLA VO streams:
o Inspect IP SLA VO streams on a hop-by-hop basis using Performance Monitor and Mediatrace.
o Use IP SLA VO over the top metrics that are collected from IP SLA from an end-to-end perspective as
shown in Configlet 8.
An example of Mediatrace running on a IP SLA VO stream can be demonstrated using Cisco Prime Collaboration
Manager (CPCM) 1.1. Figure 15 illustrates a IP SLA VO session between two Cisco Catalyst 3K switch modules.
Mediatrace has been invoked and per-hop statistics for the intermediate nodes are collected. In Figure 16,
Mediatrace reports that there are no packet losses on any of the intermediate hops. The network administrator has
a good idea as to the impact of installing TelePresence endpoints behind the two access switches.
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Figure 16. Mediatrace on IP SLA VO Session Using CPCM 1.1
Summary
1. IP SLA VO generates synthetic video traffic that is very similar to real video traffic.
2. IP SLA VO is supported on three Cisco platforms: Catalyst 3K series, Catalyst 4K series and the ISR G2
series.
3. Profiles are supported on these platforms using two methods: pre-packaged and custom.
4. Pre-packaged profiles available on these platforms are slightly different.
5. Custom profiles can be generated and used on the Catalyst 3K series and ISR G2 series.
6. IP SLA VO can be used with other Medianet technologies like Performance Monitor and Mediatrace to provide
a powerful suite of pre-deployment and troubleshooting tools for rich media applications.
References
Basic IP SLA VO configuration involves:
1. Cisco IP SLA homepage
2. White paper: Successfully delivering mission critical, performance sensitive services and applications
3. Cisco IOS
4. White Paper: Cisco IP Service Level Agreement Video Operation
5. Cisco Medianet homepage
6. Cisco Medianet media monitoring
7. White paper: Cisco IOS Performance Monitor and Mediatrace quick start guide
8. Cisco Medianet data sheet
9. White paper: Cisco IOS IP SLA user guide
10. Data sheet: High-density packet voice video DSP module
11. Software tool: Custom profile generator for Catalyst 3K switches
12. IP SLA VO configuration guide
13. Autocorrelation function
14. Cisco Prime Collaboration Manager
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Appendix A: Open Issues
A list of issues that exist with IP SLA VO across platforms are listed in Table 10. These issues are being worked on
presently.
Caveats Description
CSCtt32852 Jitter values calculated by Performance Monitor for IP SLA VO traffic is higher than for real traffic
CSCts88988 On the Catalyst 3K switches, IP SLA VO IPDV (RFC-5481) jitter stats are not accurate. This is resolved
but is not available in 12.2(58)SE2. Will be available by August 2012
CSCtu34249 Cat4K does not generate SSRC’s, thus Medianet Performance Monitor will not be able to measure
performance metrics for IP SLA-VO traffic coming from the Cat4K.
CSCtx33273 IP SLA VO aggregated stats sum certain metrics which should not be summed, but averaged over all the
tests. Avg Bit Rate, IPDV Min/Avg/Max etc
CSCtx45855 Cat4K IP SLA VO stats does not measure Latency correctly
CSCtx55732 ISR-G2 IP SLA VO emulate feature fails interop w/ CAT3K and CAT4K. This issue is resolved but is not
available on the 12.2(58)SE2 image. Will be available by August 2012
CSCty68902 When Cat 4K interops with Cat3K, it sends the amount of data in PPS (packets per second) while Cat3K
reads it as Kbps. This leads to some scaling issues with Catalyst 3K interoperability
CSCty39747 ISR G2 currently does not send the amount of data it will be transmitting to the responder. This leads to
some scaling issues with Cat3K and Cat4K interoperability
Printed in USA
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