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Understanding ICA BandwidthUsage in your Environment
Simon Frost
Product Architect
Citrix Systems
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2© 2007 Citrix Systems, Inc. — All rights reserved
Agenda
• What is ICA?
• How Much Bandwidth do you need
• Monitoring• Tuning
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3© 2007 Citrix Systems, Inc. — All rights reserved
What is ICA?
• Independent Computing Architecture
• A Protocol that supports the remoting of Application Screens from a Server to a Client
• Basic Protocol very simple
• Contains Virtual Channels for specific services• Both essential: e.g. Graphics (thinwire)• & optional: e.g. Twain Scanner redirection
• Modules negotiated at Connection handshake time
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4© 2007 Citrix Systems, Inc. — All rights reserved
The ICA StackVirtual Drivers
WinstationDriver
Protocol Driver
…
Transport Driver
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5© 2007 Citrix Systems, Inc. — All rights reserved
The WinStation DriverWinstation Driver
PRI0
PRI1
PRI2
PRI3
ICA Protocol
Compression
DataSilos
Bandwidth Management
Not All Virtual ChannelsUse General Compression
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Bandwidth Requirements
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7© 2007 Citrix Systems, Inc. — All rights reserved
How much Bandwidth will ICA use?Gigabit
GSM
wpm . compr . bw
appl . Θ . gdi(txt -9,bmp) . VC bulk
…It Depends…
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8© 2007 Citrix Systems, Inc. — All rights reserved
Bandwidth Factors
• Application Mix• Graphics Done by applications• Bitmaps / Lines / Text• Redundant Redraws• Other VC traffic required
• Client Drive / Clipboard / Printing /…
• User behaviour
• Compression
• Encryption
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9© 2007 Citrix Systems, Inc. — All rights reserved
Use of the network
• If the network is fat enough
• And there‘s no competing traffic
• And no restrictions• ICA will use more
bandwidth
vs.
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10© 2007 Citrix Systems, Inc. — All rights reserved
Bandwidth Calculation
• Well, throughput actually…
• Calculated opportunistically• Whenever sufficient data volume is available• ICA does not introduce extra traffic for bandwidth measurement
• Calculations are used to schedule datatransmission
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Monitoring
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12© 2007 Citrix Systems, Inc. — All rights reserved
Monitoring Tools
• Network Level tracing• NetMon / Ethereal / WireShark etc• Spot the Priority headers in ICA packets…
• ICA counters• SMC data
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13© 2007 Citrix Systems, Inc. — All rights reserved
Perfmon Counters
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Session Management & Control (SMC)
• Exposes instrumentation from within theWinStation driver• For the whole Session
• For each Virtual Channel• Can also be used to apply limits to bandwidth
usage
• Used to implement the limits in policy• Console Sample part of Presentation Server SDK
• You‘ll probably have to build it tho…
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15© 2007 Citrix Systems, Inc. — All rights reserved
SMC API Console Sample
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16© 2007 Citrix Systems, Inc. — All rights reserved
SMC API Console Sample
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Tuning
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18© 2007 Citrix Systems, Inc. — All rights reserved
Graphics• Thinwire uses many packing & caching tricks to
limit bandwidth used
• Redundant updates discarded
• Any image that appears ‗photographic‘ is JPEGencoded
• Level of lossy compression controllable by policy
• Graphics channel auto tunes by bandwidth• < 640 kbps – heavyweight• 640 – 2.4 Mbps – medium• > 2.4 Mbps – off
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19© 2007 Citrix Systems, Inc. — All rights reserved
CPS 4.5 Graphics• Improved handling of apps that do large numbers
of small graphics operations• ‗Progressive Display‘ mode for complex graphics
applications• CAD• DTP etc
• Show a degraded image whilst moving
• Snap to full fidelity when still
• Off by default as requires greater server resource• Configure by Policy
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20© 2007 Citrix Systems, Inc. — All rights reserved
BMP – 344K
Lossy Compression
JPG 100% - 60KLow Comp. 90% - 26K
Medium Comp. 60% - 13K
High Comp. 30% - 9K
Very High Comp. 13% - 6K
Ultra High Comp. 7% - 5K
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21© 2007 Citrix Systems, Inc. — All rights reserved
SpeedScreen Policy
Lossy Compression also applicable to TWAIN
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22© 2007 Citrix Systems, Inc. — All rights reserved
Multimedia
• Full motion video is inefficient to render via GDI• Original Compressed form expanded & displayed• ICA Encoded for Transmission• Largely overwritten
• Video Codecs take advantage of frame ‗lossyness‘ • SpeedScreen Multimedia Acceleration
• Transmits encoded video form through Virtual Channel• Displayed using client video engine
• Windows only• Tuning for buffering available• See Advanced Concepts Guide
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23© 2007 Citrix Systems, Inc. — All rights reserved
Project Apollo
• Support for 3D Graphics forms• WPF, Vista Aero, DirectX etc• Adaptable technology that takes advantage of GPUs as available• Impressive results already
• Work from here on improving performance & bandwidthrequirements
• Bitmap Remoting Tech Preview out now• Download from MyCitrix
• Also work on Flash, Audio Codecs & othermultimedia aspects
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24© 2007 Citrix Systems, Inc. — All rights reserved
Printing
• Choice of Print Drivers can make a huge differencein bandwidth requirements
• Universal Printer Driver (UPD 3) is designed toreduce bandwidth used• EMF form is highly compressible• Custom channel compression• In User Mode allowing bigger compression buffers
• Delaware switches to XPS• Even more compressible & flexible
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25© 2007 Citrix Systems, Inc. — All rights reserved
Client Drives
• Async Writes• Performance Tweak rather than Bandwidth effect
• Server told that writes completed immediately
• Any failures raised later
• Use with care• Only where operation can be retried
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26© 2007 Citrix Systems, Inc. — All rights reserved
Session Limits
• Set limits on the amount of bandwidth a sessioncan use• Or a specific Virtual Channel
• eg Printing!
• All functionality will be maintained• Some delay, especially in bulk transfer VC, can result
• Limits via
• Policy – See ‗Session Limits‘ tab of Bandwidth Policies • SMC API
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27© 2007 Citrix Systems, Inc. — All rights reserved
Bandwidth-Related Policies
• Asstd bandwidth-related policies
• Policy filters• Don‘t forget the IP filter
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28© 2007 Citrix Systems, Inc. — All rights reserved
SMC - IMetaFrameVirtualChannel2• Properties
• Get Total outbound data
ULONG BytesSent
• Get Total inbound dataULONG BytesReceived
• Get / Set Bandwidth cap in kilo-bits/second
ULONG BandwidthCapVirtual channel priority
• Get / Set VC Priority LevelPriority(MetaFrameVCPriorityLevel)
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29© 2007 Citrix Systems, Inc. — All rights reserved
Compression
• Compression is on by default
• Check for ‗Compression‘ setting in config • Note ‗1‘, ‗On‘, ‗Yes‘ all mean enabled!
• Consider ‗Maximum Compression‘ setting • Uses more memory for compression history• Enable via MaximumCompression setting
• External Compression engines currently require allbuilt in compression & encryption to be disabled
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30© 2007 Citrix Systems, Inc. — All rights reserved
Eliminate unwanted virtual channels
• Speeds up login time
• Tune via ICA config or by Policies
• Config entries are of the form• CDMAllowed Client Drive mapping VC• CPMAllowed Client Printer Mapping VC
• Channels are on by default, set to ―Off‖ to disable
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31© 2007 Citrix Systems, Inc. — All rights reserved
Where to apply ‗client side‘ tuning?
• ICA tuning can be applied in:
• PN client AppSrv.ini
• ICA Version 10 (Win32)• Now in registry• HKLM\Software\ICA Client\Engine\Configuration
• WI template.ica file• Prior to 4.0: Create new website per variant• 4.0: use bandwidth selection template files
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32© 2007 Citrix Systems, Inc. — All rights reserved
WI Bandwidth Selection
Template Files in WI site confdirectory:
Bandwidth_high.ica
Bandwidth_medium_high.ica
Bandwidth_medium.ica
Bandwidth_low.ica
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33© 2007 Citrix Systems, Inc. — All rights reserved
Small Packets
• Server -> Client• Intermittent Keepalives etc• Well compressed graphics
• Client -> Server• Keyboard & Mouse• Enable ‗Queue Mouse Movements & Keystrokes‘ • -or-• Tweak ‗MouseTimer‘ & ‗KeyboardTimer‘ params
• Defaults to 0• Queue Input or Bandwidth Low
MouseTimer 100msKeyboardTimer 50ms
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Network Tuning
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35© 2007 Citrix Systems, Inc. — All rights reserved
TCP window size
• CPS install changes TCP windows size to 63KB• Maximum throughput for bulk transfer channels
• For unreliable networks, this may be too high
• Aim for ‗Bandwidth Delay Product‘ • KB per sec * mSec delay
• Check TCP Window Size in Registry• HKLM\SYSTEM\CCS\Services\Tcpip\Parameters\TcpWindowSize
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36© 2007 Citrix Systems, Inc. — All rights reserved
Make best use of the Network
Client
Server
OutBufs
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37© 2007 Citrix Systems, Inc. — All rights reserved
What values for Outbufs?• Outbuf Count * Outbuf Len ≈ TCP Window Size
• Client -> Server (OutBufCountClient2) and
• Server -> Client (OutBufCountHost2) can bedifferent
• e.g. ADSL, Satellite, wWAN etc
• The size of the Outbuf (OutBufLength2) can becritical for performance & reliability on somenetworks• wWAN (e.g. GPRS)
• This is a Maximum size for outbufs so net effectwill depend on activity• Tune to near MTU (min 270, max 1460)
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39© 2007 Citrix Systems, Inc. — All rights reserved
•Reduce Perceived Latency with ‗Local Echo‘
• Turn on SpeedScreen Latency Reduction
• Values here: 0 – disabled, 1 – Enabled, 2 – auto.
• May need to tune for connection using ‗SpeedScreen LatencyReduction Manager‘
• High Latency Threshold (default 500ms)
• Some apps may need configuration
High Latency Connections
ZLKeyboardMode 1
ZLMouseMode 1
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40© 2007 Citrix Systems, Inc. — All rights reserved
ICA Latency Counter
• Another opportunistic counter
• Can be inaccurate
• More accurate in CPS 4.5 & 10 client but still aguideline
• Can be made much more accurate by configuring ActiveLatencyPeriodInSeconds in registry(CTX103610)
• At the moment, Active Latency calculations areblocked if session reliability is in use
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41© 2007 Citrix Systems, Inc. — All rights reserved
Conclusion
• ICA attempts to give the best experience given• The detected network connection• The settings applied
• It doesn‘t attempt to minimise bandwidth
• …but it can happily operate on restricted bandwidth
• …by virtue of detected network condictions
• …or by settings applied
• How much bandwidth…
…DEPENDS!
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