High Availability

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High Availability in OCS 2007 / 2007 R2

Office Communications Server (OCS) 2007 and R2

Bob’s OC Bob’s Phone

RegistrationRoutingPresenceConferencing

Architecture:• One monolithic Front End Service• Dependency on single shared backend database

(Registration, Routing, Presence, Conferencing)

HLB required for all traffic

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High Availability – Communications Server “14”

Microsoft Communications Server “14”

Bob’s OCBob’s Phone

User Services Database(Presence and Conferencing)

RegistrarDatabase

HLB is optional for SIP traffic(DNS LB is recommended)HLB still required for client-serverHTTP Traffic

(Registration and Routing)

3

Architecture:• Registrar Role (Registration and Routing). Each

registrar has its own SQL Express database• User Services Role (Presence and Conferencing)• Registrar and User Services are collocated in the

datacenter (but on different servers)• All user end points register with same Front End• Users are load balanced by Registrars using a

Distributed Hash Algorithm• Registrar can be installed in remote locations

Resiliency Architecture

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Architecture:1. Each user has a “Primary Registrar Pool”. Each Registrar Pool can have a “Backup Registrar Pool”2. User’s client discovers a Registrar Pool through DNS SRV. Directed to “Primary & Backup Registrar Pool”3. Backup Registrar heart-beats Primary Registrar. If heart-beat not received within Configurable Failover Interval (default = 120

sec for branch offices), Backup starts accepting client registrations

Registrar

SBA

Branch Office

Joe’s Primary Registrar = SBA., User Services = EE Pool1

Data Center - EE Pool 1

Bob’s Primary Registrar & User Services = EE Pool 1

PresenceConferencing

Registrar(Registration& Routing)

Active Directory

AD & DNS

Data Center - EE Pool 2

PresenceConferencing

Registrar(Registration& Routing)Alice’s Primary Registrar

& User Services = EE Pool 2

Active Directory

AD & DNS

BackupRegistrarPool

BackupRegistrarPool

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Data Center Voice Resiliency

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• Communications Server “14” Pool. That Communications Server “14” Pool directs client to primary and backup SIP registrar

• Client attempts connect to Primary Registrar Pool, if fails, connects to Backup

• Limited feature set available on failover

• Enable/Disable Automatic failover, Configurable Failover interval• Automatic Failback, Configurable Failback interval (No manual failback.

Workaround: Stop Front End Services on Primary Registrar pool servers)• What happens if Primary Data Center cannot be restored?

Features Available to Users In Case of Data Center Disaster

PSTN Inbound calls(if Carrier offers this resiliency)

PSTN Outbound calls

Intra-Site calls and Inter site calls

Hold, Retrieve, Transfer

Authentication, Authorization

2 Party Intra Site Instant Messaging (IM) and Audio/Video (A/V)

Call Detail Records (CDR)

Call Forwarding, SimulRingBoss-Admin, Team-call

Join conferences scheduled by users homed on other pool

Features Unavailable

Conferencing Auto Attendant (AA) (through PSTN)

Schedule IM, A/V & Web Conferences

Presence and Do Not Disturb (DND) based routing

Updating Call Forwarding settings

Response Group Service & Call Park

Voicemail Deposit (Redirect to Exchange UM in the datacenter)

Voicemail Retrieve (through PSTN)

Data Center Voice Resiliency (EE)Failover to Backup Data Center

Failover

CS “14”Edge1

CS “14”Pool 1

North America Data Center

CS “14”Edge2

CS “14” Pool 2

Europe Data Center

WAN

BackupRegistrar

• SE Servers operate as separate systems• Client DNS SRV request discovers (one or multiple) Communications Server “14” SE. That

Communications Server “14” SE sever directs client to primary and backup SIP registrar• Client attempts connect to Primary Registrar, if fails, connects to Backup• Limited feature set available on failover• Enable/Disable Automatic failover, Configurable Failover interval• Automatic Failback, Configurable Failback interval (No manual failback. Workaround: Stop

Front End Services on Primary Registrar servers)• If Primary Data Center cannot be restored:

• Restore Central management Server in backup datacenter• Restore other services including Presence, Conferencing by “moving” users to other

Pool

Data Center Voice Resiliency (SE)Failover to Backup Data Center

Failover

WANCS “14”Edge1

CS “14” SE 1

North America Data Center

CS “14”Edge2

CS “14” SE 2

Europe Data Center

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WAN

BackupRegistrar

Features Available to Users In Case of Data Center Disaster

PSTN Inbound calls(if Carrier offers this resiliency)

PSTN Outbound calls

Intra-Site calls and Inter site calls

Hold, Retrieve, Transfer

Authentication, Authorization

2 Party Intra Site Instant Messaging (IM) and Audio/Video (A/V)

Call Detail Records (CDR)

Call Forwarding, SimulRingBoss-Admin, Team-call

Join conferences scheduled by users homed on other pool

Features Unavailable

Conferencing Auto Attendant (AA) (through PSTN)

Schedule IM, A/V & Web Conferences

Presence and Do Not Disturb (DND) based routing

Updating Call Forwarding settings

Response Group Service & Call Park

Voicemail Deposit (Redirect to Exchange UM in the datacenter)

Voicemail Retrieve (through PSTN)

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1. Client DNS SRV request. Example: DNS SRV for _sipinternaltls._tcp.contoso.com2. DNS SRV Response includes

• CS Director Pool.contoso.com:5061 Priority=0, Weight=10• CSPool2.contoso.com:5061 Priority=1 , Weight=10

3. Client connects via TLS to Communications Server “14” Director Pool. Sends SIP Register. Authenticates.4. Communications Server “14” Director Pool redirects client. SIP 301 includes Primary & Backup Registrar pool5. If Primary Registrar Pool is available, client connects and registers with it6. Else client connects and registers with Backup Registrar Pool (CS Pool 2)

Data Center Voice ResiliencyFailover to Backup Data Center (Discovery)

CS “14”Edge1

CS “14”Edge2

CS “14” Pool 1

CS “14”Pool 2WAN

CS “14” DirectorPool

Active Directory

AD DS & DNS

(1)

(2) (3) (4) (5) (6)

BackupRegistrar

North America Data Center Europe Data Center

Metropolitan Data Center Resiliency

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10

Metropolitan Data Center ResiliencyCS “14” Pool Extended Across Two Data Centers

• Communications Server “14” pools operate as one logical system• Split Front End pool across two datacenters (all FEs active)• SQL Geo cluster for backend (Stretched Virtual Local Area Network (VLAN))• Data replication is done by storage arrays (Ex: EMC SRDF, HP CLX EVA)• Requires low latency WAN (15 milliseconds)

• In one site is down, clients are serviced by FEs in other site• Nearly all features available

• PSTN termination may affect inbound calls• Failback has to be manually initiated

CS “14”Edge

CS “14”Edge

FE 1-2 FE 3-4Low-LatencyWAN

NY Data Center NJ Data Center

Active SQL Passive SQL

Features Available Depending on Ex-UM Deployment

Voicemail Deposit

Voicemail Retrieve

Features Available to Users If One Data Center goes Down

PSTN Inbound calls

PSTN Outbound calls

Intra-Site calls and Inter site calls

Hold, Retrieve, Transfer

Authentication, Authorization

2 Party Intra Site IM and A/V

Call Detail Records (CDR)

Call Forwarding, SimulRingBoss-Admin, Team-call

Voice Apps (CAA, Response Group, Call Park)

Conferencing (IM, A/V and Web)

Presence and DND based routing

Updating Call Forwarding settings

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Metropolitan Data Center ResiliencyCS “14” Pool Extended Across Two Data Centers

CS “14”Edge

CS “14”Edge

FE 1-2 FE 3-4Low-Latency

WAN

NY Data Center NJ Data Center

Active SQL Passive SQL

Features Available Depending on Ex-UM Deployment

Voicemail Deposit

Voicemail Retrieve

Features Available to Users If One Data Center goes Down

PSTN Inbound calls

PSTN Outbound calls

Intra-Site calls and Inter site calls

Hold, Retrieve, Transfer

Authentication, Authorization

2 Party Intra Site IM and A/V

Call Detail Records (CDR)

Call Forwarding, SimulRingBoss-Admin, Team-call

Voice Apps (CAA, Response Group, Call Park)

Conferencing (IM, A/V and Web)

Presence and DND based routing

Updating Call Forwarding settings

DNS Server

DNS Srv

Pool.contoso.com