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Changing the Traffic Manager TTL

    Question

  • We are starting to experiment with Azure Traffic Manager and I have a question regard the TTL setting. I am wondering if there is any guidance on the pro's and cons to altering the default of this setting. In our case i would like the TTL to be as low as possible so that when my hosted services goes offline my users will quickly get routed to a failover service. Since the default is 5 minutes and it takes Traffic Mgr at least 90 seconds to notice failure it would appear by default I have a 6.5 minute window during which clients could be trying to access a failed service.

    So I'd like to dial the TTL down to 60secs, so that I have a 2.5min outage window. But what are the downsides to this? Is it simply going to mean more DNS requests coming in to the Traffic Manager because the results will be cached for a shorter time?

    What else should I be aware of?

    Wednesday, November 23, 2011 12:23 AM

Answers

  • Hi,

    We recommend you leave the setting at the default value of 300 seconds (5 minutes). More frequent times will increase the amount of traffic from clients and secondary DNS servers to Traffic Manager, potentially impacting the performance of clients or DNS servers.

    You may also find similar information in the Labs doc:

    Note: The TTL determines for how long clients and secondary DNS servers cache a DNS host entry. Clients will continue to use a given hosted service until its entry in the cache expires.  For this hands-on lab, the TTL is set to the lowest possible value to allow policy results and changes in the status of services to be seen as early as possible. Note, however, that lowering this value increases DNS traffic and that you should consider keeping its default value for your production services.

    Using a low TTL value will cost more time for clients to get response even when services are all in normal status while using a high TTL value will make clients still access failed service when that service is down.

     


    Allen Chen [MSFT]
    MSDN Community Support | Feedback to us
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    Thursday, November 24, 2011 2:47 AM

All replies

  • Hi,

    I am trying to involve someone familiar with this topic to further look at this issue. There might be some time delay.

    Appreciate your patience.

     

    Best Regards,

    Ming Xu.


    Please mark the replies as answers if they help or unmark if not.
    If you have any feedback about my replies, please contact msdnmg@microsoft.com.
    Microsoft One Code Framework
    Wednesday, November 23, 2011 3:22 PM
  • Hi,

    We recommend you leave the setting at the default value of 300 seconds (5 minutes). More frequent times will increase the amount of traffic from clients and secondary DNS servers to Traffic Manager, potentially impacting the performance of clients or DNS servers.

    You may also find similar information in the Labs doc:

    Note: The TTL determines for how long clients and secondary DNS servers cache a DNS host entry. Clients will continue to use a given hosted service until its entry in the cache expires.  For this hands-on lab, the TTL is set to the lowest possible value to allow policy results and changes in the status of services to be seen as early as possible. Note, however, that lowering this value increases DNS traffic and that you should consider keeping its default value for your production services.

    Using a low TTL value will cost more time for clients to get response even when services are all in normal status while using a high TTL value will make clients still access failed service when that service is down.

     


    Allen Chen [MSFT]
    MSDN Community Support | Feedback to us
    Get or Request Code Sample from Microsoft
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.



     


    Thursday, November 24, 2011 2:47 AM