ica bandwidth

8/10/2019 Ica Bandwidth

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Understanding ICA BandwidthUsage in your Environment

Simon Frost

Product Architect

Citrix Systems



2© 2007 Citrix Systems, Inc. — All rights reserved

Agenda

• What is ICA?

• How Much Bandwidth do you need

• Monitoring• Tuning




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




The ICA StackVirtual Drivers

WinstationDriver

Protocol Driver

…

Transport Driver




The WinStation DriverWinstation Driver

PRI0

PRI1

PRI2

PRI3

ICA Protocol

Compression

DataSilos

Bandwidth Management

Not All Virtual ChannelsUse General Compression



Bandwidth Requirements




How much Bandwidth will ICA use?Gigabit

GSM

wpm . compr . bw

appl . Θ . gdi(txt -9,bmp) . VC bulk

…It Depends…




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




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.




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



Monitoring




Monitoring Tools

• Network Level tracing• NetMon / Ethereal / WireShark etc• Spot the Priority headers in ICA packets…

• ICA counters• SMC data




Perfmon Counters




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…




SMC API Console Sample



Tuning




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




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




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




SpeedScreen Policy

Lossy Compression also applicable to TWAIN




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




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




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




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




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




Bandwidth-Related Policies

• Asstd bandwidth-related policies

• Policy filters• Don‘t forget the IP filter




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)




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




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




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




WI Bandwidth Selection

Template Files in WI site confdirectory:

Bandwidth_high.ica

Bandwidth_medium_high.ica

Bandwidth_medium.ica

Bandwidth_low.ica




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



Network Tuning




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




Make best use of the Network

Client

Server

OutBufs




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)




•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




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




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!

ica bandwidth

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