Sign-in is a tricky area.
 
It’s the most important feature — a user that cannot sign-in isn’t able to use the client.
 

What can go wrong:

After the sign-in button is pressed, the Messenger presence pawns get to dancing.

In the physical world, it’s possible to dance without a partner.  Or so I’ve heard.

 

Windows Live Messenger, being a communication client, works a lot better if it is able to communicate with other clients.  It has to perform the following steps to cross the dance floor:
  1. Authentication
    One of the key tenets of Windows Live is security.  In order to protect our users, we have to make sure that the Windows Live ID and password are correct.

    If they are correct, the pawns keep dancing.
    If they are incorrect, you will see a dialog with the following text:

    • "Windows Live Messenger could not sign you in because the Windows Live ID you entered does not exist or is incorrect.

      If you have forgotten your password, click Forgot your password? at the bottom of the main Messenger window.

      Error code: 80048821"

  2. Version Check
    Once we’ve authenticated the user, we start talking to the Messenger servers.  The server’s response includes a description that states the minimum client version it’ll support.

    Sometimes, after a release, an issue will be discovered that requires updating the released client.  In order to protect the user from experiencing the issue, the client will prompt the user to update to a newer version before continuing with the sign-in.

  3. Acquiring Contacts
    There wouldn’t be a point to a communications client if there wasn’t anyone to communicate with.  Your contact list is stored on the Windows Live servers so it can roam between your different machines and be reused throughout Windows Live.  One example of this is that all of your Messenger contacts show up in Windows Live Mail.

    If you are running WLM [Windows Live Messenger] 8.0, it is possible that you can see the following issues:

    • Empty contact list
    • Missing contacts
    • Prompts to add contacts that you’ve already added

    "Don’t Panic!"  Your contacts are still on the server and are still intact.  The reason this might occur is that we made a change to continue with sign-in, even if we weren’t able to acquire all of the contacts.

    However, in light of the feedback that we’ve received over this feature, there is a change, already available in the latest Windows Live Messenger 8.1 Beta, to fail sign-in if the client determines that it isn’t able to acquire the complete contact list.

    If we aren’t able to acquire the contact list OR we aren’t confident about the contact list we’ve previously acquired, you will see a dialog with the following text:

    • "You cannot use Windows Live Messenger at this time because your contact list is not available.  Please try again later.

      Click Help to learn more about your contact list.

      Error code: 81000378"

  4. Tripping
    There are a number of other things that can go wrong:
    • The machine doesn’t have an Internet connection.
    • The machine is behind a proxy that requires authentication, and the authentication hasn’t been set.
    • The machine runs out of memory.
    • The presence server is unavailable (possibly due to an upgrade).
    • etcetera

    If we hit any of these issues, the client will fail sync with a dialog apologizing for the inconvenience.

Recent Improvement Efforts:

  1. Performance
    In each release, the pawns are subjected to a quicker tune.  In WLM 8.0, we made sure to delay the initialization of the new features to prevent sign-in performance degradations.  The majority of sign-in scenarios are faster in WLM 8.0 than they were in previous releases.

    In WLM 8.1, there was a substantial effort to optimize resign-in, and should be noticeably better.  This ‘fast reauth’ codepath is triggered when you lose network connectivity or return to a machine after having signed in on a different machine.

  2. Resiliency
    If someone spills a drink on the dance floor, it shouldn’t prevent everyone from dancing — just move to a cleaner spot.

    In WLM 8.0 [and in WLM 8.1], we made a number of changes to Messenger so that it can function if something goes wrong.  For the majority of sign-ins, the only servers necessary are authentication and presence; to put this in context, Messenger has to talk to different servers to support the different features available in the client (examples: video chat, voice calling, instant messaging, offline messages, Windows Live Today, new mail notifications, alerts, tabs, games, etcetera).

  3. Reporting
    If all else fails, it’s important to figure out why everything failed.  Wendy covered CEIP in her recent post (Are you Experienced?!?!), and it’s one of the tools we use to measure the state of sign-in.

    In WLM 8.1, we made a number of improvements in relation to beta feedback.  So keep on posting to the newsgroups and/or submitting feedback.  I know it’s painful when sign-in doesn’t work, and we’re sorry for any problems you have, but we greatly appreciate your help and understanding on the manner. 

What to do when something goes wrong:

There are a number of resources available to our users.  [Most of these were discussed in better detail in Nicole’s "Help! Feedback! Marco! Polo!" post]

  1. Connection Troubleshooter
    This tool, built into Messenger, can be run to help Messenger self-diagnose the problem.

    It is launched by opening the available under: "File->Tools->Options…" menu item.
    Clicking the "Connections" tab.
    Pressing the "Start…" button in the "Connection Troubleshooter" section.

  2. Service Status
    There is a link at the bottom of Messenger’s main window called ‘Service Status‘.  This will open up a webpage that is kept up-to-date with the status of the servers used by Messenger.
  3. Support Blog
    Messenger Support has their own blog (http://messenger-support.spaces.live.com/).
  4. Newsgroups
    There are a number of helpful people on the aforementioned Windows Live Messenger Newsgroup.  Search there to see if others have already started a thread with a similar problem, and open a new topic if you don’t find anything.
  5. Support
    When all fails, you can contact Messenger support.
 
If you have a comment/question/concern/discussion topic/rant/rave/other – please head over to the Windows Live Messenger Newsgroup.