HTTP Flood Mitigation causing slow Exchange Mailbox Migrations to Office 365

It's been a while since I've updated this blog as I've been busy rolling out content internally in Microsoft to help our customers connect to our cloud services. I do have some new tips around checking routing and ISP performance that I'll write up soon and publish. However, my colleagues have run into an issue…

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How to analyse Application level performance for Outlook and SharePoint online

If we've stepped through all the network level checks and all looks good from that perspective, then we need to move up the stack to the application itself and see if something above the network is causing performance issues. This can prove tricky with Office 365 as the information is almost always encrypted within an…

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Checking your TCP Packets are pulling their weight (TCP Max Segment Size or MSS)

This is a quick one to check to ensure your TCP packets are able to contain the maximum amount of data possible, low values in this area will severely affect network performance. Maximum Segment size or MSS is a TCP level value which is the largest segment which can be sent on the link minus…

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Ensuring your TCP stack isn’t throwing data away

Fw In my previous blog post, I discussed checking the MSS to ensure full sized packets are used. Well, whilst you're digging around in the TCP Options of the SYN-SYN/ACK packets, it's worth checking another option SACK or Selective Acknowledgement. As you most likely know, TCP is a reliable protocol, in that it ensures delivery…

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Ensuring your Proxy server can scale to handle Office 365 traffic

Proxy servers are often in place at customer sites, happily ticking away handling Internet traffic for years before Office 365 came along. As Office 365 generally travels over port 443 (for Outlook and SharePoint at least) then what's to think about? Your proxy can handle this like any other SSL traffic right? Well, yes technically…

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Top 10 Tips for Optimising & Troubleshooting your Office 365 Network Connectivity

Having performed numerous Office 365 Network assessments and reactive visits to resolve issues for customers, its apparent that the vast majority of issues are seen time and time again. So from this experience, here are my top 10 tips for you to optimise your O365 network performance and prevent issues occurring in future. Some of…

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Checking your DNS performance isn’t delaying your O365 connections

  One of the initial things which should be checked is name resolution, a point which is often forgotten when doing performance tests. If the name resolution takes time, then this will manifest itself as initial page load time slowness in SharePoint. It's less visible with Outlook but little delays in DNS, and proxy authentication…

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Preventing proxy authentication from delaying your O365 connection

A quick and easy check you can do to ensure your O365 connections complete quickly is to check proxy authentication is completing quickly, or better still not being done at all. If you're not using a proxy and are going direct, then you can move along…nothing to see here! It's surprisingly common and I've run…

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How to measure the Network Round Trip Time to Office 365

One of the jobs I do fairly often is to help customers work out the performance of their network connection to office 365 from various sites to ensure it's within the limits which will give good user performance with Outlook, SharePoint etc. We have various tools available that do some level of network check for…

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