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Table Of Contents
DistributedDirector Boomerang Support
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Setting DistributedDirector and DRP Clock Synchronization
Configuring the Default Metric
Specifying the Host Priority of the Boomerang Metric
Verifying Boomerang Information
Setting DistributedDirector and DRP Clock Synchronization Example
Configuring the Default Metric Example
Specifying the Host Priority of the Boomerang Metric Example
ip director default priorities
DistributedDirector Boomerang Support
Feature History
This document describes boomerang support for DistributedDirector in Cisco IOS Release 12.2(8)T. It includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
Boomerang is a Director Response Protocol (DRP) metric for DistributedDirector. The boomerang server provides a way to select a content server with the fastest response time from a group of redundant content servers. Instead of relying on static maps, boomerang dynamically recognizes problems such as congestion and link failures and avoids them. The content server with the fastest response time, as determined by the priority of the configured metrics, is determined to be the best site.
When the boomerang metric is active, DistributedDirector instructs the DRP to send Domain Name System (DNS) responses directly back to the querying client. The DNS response contains the addresses of the sites associated with the particular DRP agent. All involved DRPs send back their DNS responses at the same time. The packet of the DRP that is closest to the client will arrive first. The client may take the first answer and ignore subsequent ones, a standard behavior of all local DNS server implementations. The DRP agent allows configuration for full boomerang support.
The boomerang metric may or may not be used by DistributedDirector. Whether the boomerang metric is used depends on whether other metrics are specified at higher priority (and therefore have a lower priority number) than the boomerang metric. If a metric at higher priority successfully determines the best site, then that is what DistributedDirector uses. DistributedDirector reaches the boomerang metric only if all other metrics of higher priority than boomerang are unable to determine the best site.
If and when the boomerang metric is reached, all other metrics after it (that is, metrics that have a lower priority and a higher priority number) are effectively ignored. They are ignored because the actual resolution of the best site is determined not by DistributedDirector but by which boomerang reply reaches the DNS client first. DistributedDirector is not made aware of the best site as determined by the boomerang metric.
The boomerang metric can be used alone or along with other metrics at the same or different priority levels. If boomerang is specified at the same priority as other metrics, then boomerang decides the best site. If boomerang is specified with other metrics at different priorities, then the higher-priority metrics are examined in turn until there is no tie among sites, with the result that the best site can be determined. If the consideration extends to the boomerang metric, then boomerang is the deciding metric. All other metrics of a higher priority number (lower priority) than boomerang are ignored. The concept of weight does not apply to the boomerang metric.
The DRP is a simple User Datagram Protocol (UDP)-based application developed by Cisco Systems. It enables the Cisco DistributedDirector product to query routers (DRP Server Agents) in the field for Border Gateway Protocol (BGP) and Interior Gateway Protocol (IGP) routing table metrics between distributed servers and clients. DistributedDirector, a separate standalone product, uses DRP to transparently redirect end-user service requests to the topologically closest responsive server. DRP enables DistributedDirector to provide dynamic, scalable, and "network intelligent" Internet traffic load distribution among multiple geographically dispersed servers.
DRP Server Agents are border routers (or peers to border routers) that support the geographically distributed servers for which DistributedDirector service distribution is desired. Note that, because DistributedDirector makes decisions based on BGP and IGP information, all DRP Server Agents must have access to full BGP and IGP routing tables.
Benefits
The boomerang metric provides a way to select a site with the fastest response time. Instead of relying on static maps, it dynamically recognizes congestion and link failures and avoids them.
Restrictions
Both DistributedDirector and the DRP agents should be able to communicate with each other using the boomerang protocol. Therefore, when DistributedDirector is upgraded to include the boomerang functionality, the DRP agents must be made aware of the presence of the boomerang protocol.
Related Features and Technologies
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Related Documents
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Supported Platforms
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Determining Platform Support Through Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Feature Navigator. Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Feature Navigator is a web-based tool that enables you to quickly determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image.
Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Feature Navigator home page at the following URL:
Supported Standards, MIBs, and RFCs
Standards
No new or modified standards are supported by this feature.
MIBs
No new MIBs are supported by this feature.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new RFCs are supported by this feature.
Prerequisites
You must be using DistributedDirector with DRP metrics, including boomerang.
Configuration Tasks
See the following sections for configuration tasks for the boomerang metric feature. Each task in the list is identified as either required or optional.
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Setting DistributedDirector and DRP Clock Synchronization
To activate clock synchronization between of the DistributedDirector and the DRP clocks, use the ip director drp synchronized command.
Router(config)# ip director drp synchronized
Activates or deactivates clock synchronization between DistributedDirector and the DRP.
To deactivate clock synchronization between DistributedDirector and DRPs, use the no ip director drp synchronized command.
Router(config)# no ip director drp synchronized
Deactivates clock synchronization between DistributedDirector and the DRP.
Configuring the Default Metric
To set the boomerang metric as the default metric, use the ip director default priorities boomerang command.
Router(config)# ip director default priorities boomerang 1
Configures DistributedDirector to select a server using the boomerang metric at priority level num, where num is 1.
To remove boomerang as the default metric, use the no ip director default priorities boomerang command.
Router(config)# no ip director default priorities
Removes boomerang as the default metric.
Specifying the Host Priority of the Boomerang Metric
To configure the order in which DistributedDirector considers metrics when selecting a server, use the ip director host priority command.
Router(config)# ip director host boom1 priority boomerang
Configures DistributedDirector to select a server using the boomerang metric, where hostname is boom1.
To deactivate all priorities on all metrics associated with the defined hostname, use the no form of this command.
Router(config)# no ip director host boom1 priority
Deactivates all priorities on all metrics associated with the defined hostname, where hostname is boom1.
Verifying Boomerang Information
Step 1
Router# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30ip director server 172.2.2.20 drp-association 172.4.4.2ip director server 172.2.2.30 drp-association 172.4.4.3ip director server 172.2.2.10 drp-association 172.4.4.1ip director host boom1no ip director cacheip dns primary boom1 soa boom1 boom1@comip director host boom1 priority boomerang 1no ip director drp synchronizedStep 2
Router# show ip directorDistributed Director status:Queries received: 0Queries replied: 0Queries received in the last second: 0Queries received in the last minute: 0Incomplete information selections: 0TTL for reply RRs when sorted by DD: 0 secsQueries awaiting processing by DD: 0Queries awaiting metric info = 0Director cache is onCache time for sort cache entries: 60 secsDirector sort cache hits = 0Director Response Protocol:0 requests, 0 replies, 0 requeries, 0 bad repliesAuthentication key-chain "not defined"Output queue length = 0Maximum DRP query retry number = 2Timeout for each DRP lookup query = 1 secsTimeout for each DRP measurement query = 4 secsStep 3
Router# show ip director host boom1Host boom1 (A queries):Queries received: 0, queries replied: 0Servers:Server 172.2.2.10:Advertised 0 times as best server, last at neverServer status: Untested, updated neverHost specific priorities:Boomerang evaluation = 1
Configuration Examples
This section provides the following configuration examples:
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Setting DistributedDirector and DRP Clock Synchronization Example
In the following example, DistributedDirector and DRP clock synchronization is activated:
Router(config)# ip director drp synchronizedRouter# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30ip director server 172.2.2.20 drp-association 172.4.4.2ip director server 172.2.2.30 drp-association 172.4.4.3ip director server 172.2.2.10 drp-association 172.4.4.1ip director host boom1...ip director drp synchronizedConfiguring the Default Metric Example
In the following example, the boomerang metric is specified with a priority of 1:
Router(config)# ip director default priorities boomerang 1Router# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30...ip director host boom1no ip director cacheip dns primary boom1 soa boom1 boom1@comip director host boom1 priority boomerang 1Specifying the Host Priority of the Boomerang Metric Example
The following example specifies the per-host priority of the metric, with a host named boom1, where the DRP internal metric is specified with a priority number of 1 and boomerang is specified with a priority number of 2:
Router(config)# ip director host boom1 priority drp-int 1 boomerang 2Router# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30...ip director host boom1no ip director cacheip dns primary boom1 soa boom1 boom1@comip director host boom1 priority drp-int 1 boomerang 2Command Reference
This section documents new and modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.
New Commands
Modified Commands
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ip director default priorities
To set a default priority for a specific metric on the DistributedDirector, use the ip director default priorities command in global configuration mode. To remove a default priority for a metric, use the no form of this command.
ip director default priorities [drp-int num] [drp-ext num] [drp-ser num] [random num] [admin num] [drp-rtt num] [portion num] [availability num] [route-map num] [boomerang num]
no ip director default priorities [drp-int num] [drp-ext num] [drp-ser num] [random num] [admin num] [drp-rtt num] [portion num] [availability num] [route-map num] [boomerang num]
Syntax Description
Defaults
No default priorities are specified.
Command Modes
Global configuration
Command History
Usage Guidelines
Not all of the metrics need to be specified, but at least one must be specified. If the boomerang metric is specified for a given host name, then all metrics of lower priority (that is, having a higher priority number) than boomerang are always ignored.
The default priorities specified will take effect if no priorities are specified in the ip director host priority command or in the corresponding Domain Name System (DNS) text record for the host.
To set the default priority for several metrics, enter the metric keywords and values to be configured on the same line as the ip director default priorities command.
Examples
In the following example, the boomerang metric is selected as the default priority:
Router(config)# ip director default priorities boomerang 1Router# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30ip director server 172.2.2.20 drp-association 172.4.4.2ip director server 172.2.2.30 drp-association 172.4.4.3ip director server 172.2.2.10 drp-association 172.4.4.1ip director host boom1no ip director cacheip dns primary boom1 soa boom1 boom1@comip director host boom1 priority boomerang 1no ip director drp synchronizedRelated Commands
ip director drp synchronized
To activate clock synchronization between DistributedDirector and Director Response Protocol (DRP), use the ip director drp synchronized command. To deactivate synchronization between the clocks in DistributedDirector and the DRPs, use the no form of this command.
ip director drp synchronized
no ip director drp synchronized
Syntax Description
This command has no arguments or keywords.
Defaults
Clock synchronization is deactivated.
Command Modes
Global configuration
Command History
Usage Guidelines
This command is used in conjunction with boomerang racing.
When the ip dir drp synchronized command is configured, DistributedDirector specifies an absolute time at which the DRP agent should respond to the DNS client.
When no ip director drp synchronized is configured (which is the default), DistributedDirector specifies a relative time (based on the delay measured between DistributedDirector and the DRP agent) at which the DRP agent should respond to the DNS client.
Examples
In the following example, DistributedDirector and DRP clock synchronization are activated:
Router(config)# ip director drp synchronizedRouter# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30ip director server 172.2.2.20 drp-association 172.4.4.2ip director server 172.2.2.30 drp-association 172.4.4.3ip director server 172.2.2.10 drp-association 172.4.4.1ip director host boom1...ip director drp synchronizedip director host priority
To configure DistributedDirector to select a server using the boomerang metric at a specified priority level, use the ip director host priority command in global configuration mode. To deactivate the priorities on metrics associated with the defined host name, use the no form of this command.
ip director host hostname priority [drp-int num] [drp-ext num] [drp-ser num] [random num] [admin num] [drp-rtt num] [portion num] [availability num] [route-map num] [boomerang num]
no ip director host hostname priority [drp-int num] [drp-ext num] [drp-ser num] [random num] [admin num] [drp-rtt num] [portion num] [availability num] [route-map num] [boomerang num]
Syntax Description
Defaults
No default priorities are specified.
Command Modes
Global configuration
Command History
11.1(18)IA
This command was introduced.
12.2(8)T
The boomerang metric was added.
Usage Guidelines
Not all of the metrics need to be specified, but at least one must be specified. If the boomerang metric is specified at a given priority level, then all other metrics of lower priority (that is, having a higher priority number) for that host name are ignored. If the boomerang metric is being considered, then it is the final step in determining the best server.
The availability keyword allows the DistributedDirector to attempt to create a TCP connection to each distributed server on a configured port over a configurable time interval.
If multiple metrics have the same priority value, the metrics are added together to obtain a composite metric. For example, if two metrics have the same priority value, they are first multiplied by their weight values (if specified) and then added together to form the composite metric.
If you do not specify weights for a group of distributed servers, there are no default weights for DistributedDirector, and if you have specified priority values, the weight values are set to 1.
Any metrics that have a nonzero weight and that are assigned no priority value are set to a priority value of 101. They are considered after all other metrics that have priority values. As a result, if no priority values are specified for any metric, metrics are treated additively to form one composite metric.
If you do not use priority settings and multiple servers have the same metric value, the server whose last IP address was looked at will be returned as the best server. If you want to return a random IP address in the case of a tie, use metric priority with the random metric as the last criterion.
Use the hostname argument to name the host that maps to one or more IP addresses. Do not use an IP address.
Examples
The following example specifies the per-host priority of the metric, with a host named boom1, where the DRP internal metric is specified with a priority number of 1 and boomerang is specified with a priority number of 2:
Router(config)# ip director host boom1 priority drp-int 1 boomerang 2Router# show running-configip host boom1 172.2.2.10 172.2.2.20 172.2.2.30...ip director host boom1no ip director cacheip dns primary boom1 soa boom1 boom1@comip director host boom1 priority drp-int 1 boomerang 2Related Commands