Exchange in Low Bandwidth Environments

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Exchange In Low Bandwidth Environments Tim
UptonAnjura Technology CorporationTim
Upton_at_Anjura.com
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(No Transcript)
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Overview

• Client considerations
• Topology
• Connectors
• Public folders
• System messages
• Tools and troubleshooting

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Limited Bandwidth Situations

• Low throughput WANs
• Frame relay with low CIR (16/64)
• Overburdened WANs
• Dial-up links
• Dynamic RAS
• Dial-on-demand routers
• Satellite links
• High latency

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Users Remote from Server
Exchange Server
WAN
Remote User
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Users Remote from Server

• Can do direct connection
• If messages are small
• If link is always there (reliable)
• Deadly with large attachments
• Otherwise
• Local client storage
• .PST
• .OST

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.PST

• () Fast client response time
• (-) Loss of single instance store
• (-) Loss of centralized backup
• (-) Workgroup messages consume more bandwidth
• (-) Many functions unavailable if WAN is down

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.OST

• Messages in store are backed up
• More functions are local
• Directory (Less functional searching)
• Public Folders
• Certificates
• (-) OST and each synchronized folder must be
  recreated after changing distinguished name
• Better in Outlook 2000

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.OST

• Outlook 98 - Many Improvements
• Background sync
• Scheduled sync
• Filtered sync
• Outlook 2000 - Even Better!
• Schedule updates per folder or group of folders
• Free/Busy info available by FTP

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Which Client To Use?

• Can use other client protocols
• Browser HTTP (OWA)
• Outlook ExpressIMAP4/POP3/LDAP
• but
• less functionality
• Slow
• Cumbersome
• Login is harder
• MAPI is still most efficient

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Client ConsiderationsCool Example

• NASA Space Shuttle
• Remote (Earth) server
• Low Bandwidth
• Expensive Links
• Astronauts worked offline
• OSTs were updated during flight
• Dont complain about your WAN!

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Third Party Add-Ons

• CompressMail
• Travelling SoftWare
• Compress Encrypt (Entrust)
• Check slipstick.com/addins/compression.htm

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Topology Impact

• Site boundaries
• Connectors
• Traffic within a site
• Traffic between sites

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Traffic Within A Site
One Site
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Within A Site

• Any-to-any server-to-server RPC communication
• Directory updates within five minutes
• KCC runs every three hours
• 64K available bandwidth
• (rule of thumb)

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Between Sites
Exchange Server
Exchange Server
WAN
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Between Sites

• Low bandwidth Lots of sites
• Lots of sites Lots of routes
• Keep routing simple
• Hub(s) and spoke is desirable
• Follow WAN topology
• Shortcut routes Yikes !!!
• Routing table grows significantly
• Set Least Cost Routing on Hubs

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Least Cost Route on hubs
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No Shortcuts!
X
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Connector Selection

• Site Connector
• Dynamic RAS
• SMTP
• X.400

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Connector SelectionSite Connector

• Great if you have the bandwidth
• Simple
• CPU efficient
• Fault tolerant Shared among servers

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Connector SelectionDynamic RAS Connector

• When no WAN exists
• Possible backup connector
• Better off to put redundancy into the WAN
• More likely to use dial capabilities of SMTP
  connector

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Connector SelectionSMTP Connector

• Great if the Internet is your backbone
• Requires more CPU
• Uses more bandwidth
• Messages are converted to MIME - 30 bigger
• Can use SSL Encryption on the wire

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Connector SelectionX.400 Connector

• The low bandwidth connector
• Highly tune-able (more on this shortly)
• Lots of control
• Message size
• Schedule
• (-) Tied to a server
• Less fault tolerant
• (-) Visible on the wire

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Connector SelectionX.400 Connector - Visible
B1 84 FA 3F 0B 00 00 00 52 65 78 20 42 75 74 6C
...?....Rex.Butl 65 72 00 E4 84 39 40 05 00 00 00
52 45 58 42 00 er...9_at_....REXB. 40 00 07 30 80 9D
31 CA B9 85 BE 01 40 00 08 30 _at_..0..1....._at_..0 F0
14 4E D6 B9 85 BE 01 B1 84 1D 0E 07 00 00 00
..N............. 53 65 6C 6C 21 21 00 B1 84 35 10
3C 00 00 00 3C Sell!!...5.lt...lt 44 31 36 45 38 43
44 32 39 35 46 31 44 32 31 31 D16E8CD295F1D211 41
33 43 31 30 30 36 30 36 37 34 04 32 30 37 45
A3C10060674B207E 31 35 32 41 40 70 6F 77 65 72 32
2E 6D 61 72 63 152A_at_power2.marc 68 76 69 65 77 2E
63 6F 6D 3E 00 03 00 00 40 D1 hview.comgt...._at_. 6E
8C D2 95 F1 D2 11 A3 C1 00 60 67 4B 20 7E 00
n.........gK.. 37 99 00 00 00 54 68 65 20 64 65
61 6C 20 77 69 7....The.deal.wi 74 68 20 4D 69 63
72 6F 73 6F 66 74 20 68 61 73 th.Microsoft.has 20
66 61 6C 6C 65 6E 20 74 68 72 6F 75 67 68 20
.fallen.through. 61 6E 64 20 6F 75 72 20 63 61 73
68 20 66 6C 6F and.our.cash.flo 77 20 69 73 20 69
6E 20 74 68 65 20 74 6F 69 6C w.is.in.the.toil 65
74 2E 0D 0A 0D 0A 53 75 67 67 65 73 74 20 79
et.....Suggest.y 6F 75 20 73 65 6C 6C 20 79 6F 75
72 20 73 68 61 ou.sell.your.sha 72 65 73 20 61 6E
64 20 6C 65 61 76 65 20 74 68 res.and.leave.th 65
20 63 6F 75 6E 74 72 79 2C 20 77 68 69 6C 65
e.country,.while
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Controlling Traffic

• Users
• Limit Message sizes
• System Messages
• Directory Replication
• Public Folders

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Controlling Traffic - Users

• Restrict Message Size
• Users Level
• Hard to maintain
• Use Scripting
• MTA Level
• Often Overlooked
• When site spans the WAN
• Connector Level
• Lots of flexibility

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Scenario Send Attachment at Night

• Use Multiple X.400 connectors
• Day Connector
• Small Messages (e.g lt1MB)
• Open 24 hours
• Night Connector
• Large messages (e.g. 1-5MB)
• Open at night

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Scheduling Large Messages
Message Size Limit 5 MB Active Schedule
6pm-6am
NIGHT
Message Size Limit 1 MB Active Schedule
Always
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System Traffic
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Controlling System Traffic

• System messages can add up!
• Sources
• Directory replication
• Address book views
• Public folder content/hierarchy
• Public folder replication status messages
• Link monitors
• Server monitors (RPC traffic)
• Others

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Directory Replication

• Two messages sent from each site for every other
  site

110 Sites x 2 Message / site x 109
Every other site -------- 23,980 Messages/
Dir-rep cycle 23,980 Replies --------
47,960 X 2 2 Rep cycles per day --------
95,920 Directory messages/day
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Default Directory Replication Schedule
Default 8 Times/day
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Directory Replication

• Replication data compressed 51
• Small messages not compressed
• Enable Dir-Rep logging to see compression
  messages (Event Viewer)
• Dir-Rep requests sent when DS starts up
• Can be disabled in Exchange 5.5 SP1
• Dont select hourly slots since this generates
  four dir-rep cycles

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Public Folders

• Hierarchy info replicated immediately
• Content status messages replicated at scheduled
  time
• Disable replication messages at startup (5.5 SP1)

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Public Folder Strategies

• Replicate only what needs to be replicated
• Frequently accessed data
• Objects that cant be loaded over the WAN (e.g.,
  PPTs)
• Schedule replication for off hours
• Set replication messages priority to Low

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Public Folder Backfill

• When a replica is missing data
• Good Keeps all PF in sync
• Bad Hard to control
• IS requests update from another replica
• Second request sent if backfill not complete
  within 12 hours!
• May cause extra backfill
• Backfills may come from wrong place

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Public Folder Registry Tuning

• Replication send status
• Timeout (24 hrs)
• Alignment (12 hrs)
• Disable replication messages at startup (5.5 SP1)

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MTA Tuning

• Parameters set at
• Site
• Connector
• RTS
• Connection retry
• Association
• Transfer timeouts

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MTA Tuning
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MTA Tuning

• Checkpoint size
• Default 30K
• Decrease Unreliable links
• Increase Slow, but reliable links
• Associations
• Lifetime
• Default 300 seconds
• Real short for Dynamic RAS
• Fewer Associations avoid overhead

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Per Connector Limits

• New in SP1
• Restrict
• System messages
• Based on priority
• New in SP2
• Dont open a connection until n messages or
  KBytes

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Per Connector Limiting

• Limit messages to a connector
• Type (system messages)
• Priority (High/normal/low)
• Override schedule for urgent messages
• Downgrade High Priority X.400 Mail
• Set via Heuristics Connector Attribute
• Admin Raw Mode (Admin /r)

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Connector Heuristics
E.g. Prohibit System and Low importance 4096
65536 69632
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Connector Heuristics
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Scenario

• Small Messages 24hrs/day
• Large Messages at night
• Prohibit System messages from DAY connector
• Prohibit PF traffic from DAY connector
• Allow some users (e.g. VP) to send large messages
  anytime!

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Connector Heuristics
Message Size Limit 5 MB Active Schedule
6pm-6am Override for Urgent messages 131072
NIGHT
Message Size Limit 1 MB Active Schedule
Always Prohibit System, Low priority 69632
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Only 1 Server At Each End?

• Configuring X.400 Connector between Two Exchange
  Servers
• (Q198722 5.5 SP1)
• Leave Stack Incoming TSAP blank
• Match outgoing TSAP on connectors

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Two X.400s, 2 Machines
NIGHT
Day
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ToolsDigging out of problems

• MTACheck.EXE
• /DR remove all Dir-Rep messages
• /DP remove all public folder replication
  messages
• PFADMIN (BORK)
• Fix replication schedules
• ISO decoder (BORK)
• Network monitor X.400 decode

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Tools(continued)

• Message tracking
• Crystal Reports - top talkers
• MTAView (BORK)
• See inside the MTA
• WAN bandwidth simulator
• e.g., ADTTech
• MailStorm/LoadSim

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ToolsManagement

• Scripting
• Deploy standardized configurations
• Check/update all servers worldwide
• Demo
• Adjusting X400 Connector heuristics worldwide

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Third Party Tools(Not an endorsement)

• Packeteer
• Network layer priortization
• Guarantee Bandwidth available to Exchange
• Make sure Exchange does not hog the WAN
• www.packeteer.com

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Third Party Tools(Not an endorsement)

• OnAir Mobile
• Outlook client level Driver
• Compresses Outlook Data
• Requires Server based component
• Decompress
• Ideal for Extremely low bandwidth
• Satellite, packet radio, cellular
• Working on Server to Server component
• www.OnAir.net

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More Info

• TechNet
• Backbone White Paper
• Client Traffic Analysis
• X.400 Tuning
• Other MEC99 Sessions
• 3-304 Managing Exchange with WSH
• 1-310 Planning for new Transports

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Questions
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