Forum core network upgrade

We will shortly be upgrading the remaining Forum core network switch.  With this one there will be some (expected) visible effects, as follows:

  1. This switch is normally the “root bridge” for the entire Informatics network.  While we do have extensive redundant connectivity, the active paths are usually based around this switch being at the centre.  To minimise the effect of removing this switch from the network we will deprioritise it in advance, at an off-peak time, which will have the effect of rebalancing the spanning-tree to use a different root.  After the replacement switch is installed and configured, and we are happy with the way it is running, we will again rebalance the spanning-tree back to using this switch as its root.  On each of these occasions we anticipate there may be a few seconds of network disruption while the spanning-tree is recalculated.
  2. Being at the centre of the Forum network, we normally use this switch as the primary router for most of our subnets.  To allow time for DHCP-configured hosts to pick up the change we will move this function to a different core switch a couple of days ahead of the upgrade.    Other than a visible change in path and a little extra load on our intra-core links there should be no effect from this change.
  3. While the upgrade is being carried out the link to the Forum’s external router will fall back from 10Gbps to 1Gbps.  There is a chance that external connectivity will appear slower while the upgrade is taking place as a result of congestion on this slower link.  We will try to minimise this by making this router’s link one of the last to be removed from the old switch and one of the first to be made to the replacement.

Apologies in advance for any disruption this work causes.  This is the last of the old Forum core switches to be replaced.  They were bought new over ten years ago when we moved into the Forum, firmware is no longer being released for them, and the replacements are considerably more powerful and so better able to handle the additional load from Bayes as well as the faster Forum edge connectivity.

Technical network documentation is here.

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Computing Help updates

The computing help elves have been busy. In the past few weeks they’ve overhauled the pages on Printing and on Audio-visual facilities. In particular there are now pages on AV in Appleton Tower (formerly not covered at all) and AV in the Informatics Forum (formerly split over many pages).

If you’re looking for help or information on the computer systems in the School of Informatics, take a look at computing.help.inf.ed.ac.uk – you might learn something.

With over 300 pages of technical advice, keeping our computing help pages accurate is something of a Sisyphean task, so perhaps it’s inevitable that some get missed. If you find any inaccurate or outdated information there, please let us know. (Here’s where to find us.)

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Network disruption yesterday

Apologies for the short network disruption yesterday afternoon.  It was caused by a 10Gbps forwarding loop, which was created as the second-last fibre was being connected as part of our core switch upgrade programme.  As soon as we realised there was a problem the fibre was disconnected again and the port configuration corrected.

Background: we (Informatics, and the constituent Departments before that) set up our network with redundant paths for resilience, using Rapid Spanning Tree Protocol to manage the links and prevent loops.  EdLAN as a whole has different constraints, and they run a different STP variant across the core and no STP at the edge.  Over the years there have been incompatibilties between the way these variants operate, and we have seen some instability as a result of STP-related events elsewhere.  We have therefore for some time filtered BPDUs at all of our interfaces to EdLAN.  This has generally operated well for many years.

So what went wrong yesterday?  The cards in the new switch which was being installed yesterday are slightly different from the ones in the old switch, and the port involved in yesterday’s problems was previously set up as a hot-spare EdLAN link.  (We keep some links pre-configured so that they can be quickly swapped into operation should there be a fault with our principal link.)  As part of the upgrade process that port became one of our “normal” infrastructure links and the hot-spare EdLAN link was moved to a different port.  The VLAN configurations were moved correctly, but the BPDU filtering was accidentally left applied to the wrong port.  When that port was patched in, therefore, STP did not know to block one of the downstream links, and so a loop was set up.  Unicast traffic would still have been operating normally, but we have enough multicast traffic that was looped around to completely saturate our infrastructure links.

The fix was to disconnect the problem link, so breaking the loop.  The BPDU filter was then applied to the correct link, and everything connected up again.

As usual, our technical network documentation is here.

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Informatics network core upgrade

We will shortly begin the process of upgrading the switches which form the core of the Informatics network in the Forum and Appleton Tower.  The network has enough resilience built into it that this can happen mostly transparently to users.  Where this is not possible, an announcement will be posted in advance, though actual downtime is expected to be only a few seconds while fibre is re-patched.

The switches which form the existing network core in the Forum date back to when we occupied the building, and those in the Appleton Tower core are nearly as old.  With the connection of the Informatics floors of the Bayes Centre to the Forum core, it was decided that the time had come to replace that core with more modern, powerful models, which also offer better possibilities for interaction with the new EdLAN which the University is currently procuring.  At the same time, HPE’s range and pricing structure made it advantageous to replace the AT core as part of the same process.

We’ll work through the six switches over the next few weeks, taking one down at a time, transferring cards from the old to the new switch where possible, racking up the new switch, and setting it up with (almost) the same configuration as the old one.  The process will, of course, be spread out to allow adequate testing of each replacement before moving on to the next one.

Technical documentation on the Informatics network can be found here.

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Virtual DICE has been renewed

We’ve made a new version of Virtual DICE for the new session. Virtual DICE is the lightweight DICE-like virtual machine which you can install and run on your own computer (here’s how to install it).

We release a new version of Virtual DICE twice a year. This version has the hostname tiepolo. It has most of the same software as DICE machines.

If you have an earlier version of Virtual DICE you should upgrade to the new version. To do that, make backup copies of whatever files you want to keep (for example, copy them to your AFS home directory – and here’s how to access AFS from Virtual DICE) then shut down and delete your Virtual DICE version, then install the new tiepolo version instead.

To find out more read the Virtual DICE help pages.

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Remote desktop service

Next Tuesday (4th September) the remote desktop service which uses the NX technology – nx.inf.ed.ac.uk – will be decommissioned. It will be replaced by a new service which is based on RDP – xrdp.inf.ed.ac.uk – see the computing help page for details.

The machine hosting this service – hammersmith – also needs to be reinstalled and we need to apply some important firmware updates so we expect the service to be unavailable for the whole morning.

If you have any queries about this please contact the Computing Team via the usual support form.

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Scientific Linux 7.5 Upgrade

The 5th minor update for ScientificLinux 7 (which is based on RHEL7) is now ready for deployment to the Informatics DICE office and student lab machines. A minor update like this provides us with the opportunity to update important software and fix any bugs which are not security issues (we apply security updates as soon as they are available) in a controlled manner.

Notable updates include a switch from VirtualBox 5.1 to 5.2, libreoffice is upgraded from 5.0.6.2 to 5.3.6.1, QT5 is upgraded from 5.6.2 to 5.9.2 and R is upgraded from 3.4.2 to 3.5.0. Along with the general updates this platform upgrade also provides a fully supported python 3 environment based on version 3.4.8 which includes the full “scientific python” stack of scipy, numpy, matplotlib, ipython, pandas, etc.

We plan to make this change on the evening of Monday 20th August. This has been scheduled so that it is after the exam resits have finished but still well before the start of Semester 1 so that teaching staff have sufficient time to test their course work. If you would like to have any of your DICE machines upgraded sooner that can be arranged, please get in touch.

SL7.5 was released on May 10th 2018 and since then it has been thoroughly tested in our DICE environment so we are confident that this update will not cause any issues for users.

Full details of the package updates are available on the LCFG wiki. For further, in depth information, there are also release notes from ScientificLinux and Redhat.

If you have any questions or problems with the upgrade please contact our User Support team using the support form.

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Remote wake-up service unavailable this weekend

Our remote wake-up service will be down this weekend, 14-15 July, because of planned work to the electricity supply in the James Clerk Maxwell Building. Sorry for the inconvenience. It should be back to normal on Monday morning.

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New DICE remote desktop service

For the last 5 years we have provided a remote DICE desktop service which is based on the NX technology. Although this system has some nice benefits, particularly being light on bandwidth requirements, the technology is beginning to show its age and there is a serious shortage of good client software for many platforms.

With this in mind we have made the decision to switch to providing an RDP based service. This has very good client support for all platforms (Windows, MacOSX and Linux). Currently we are at the stage of being able to offer staff users early access to a test version of the service at staff.xrdp.inf.ed.ac.uk. We’re hoping that people will try it out and report back any problems they experience. Full information on how to use the service is available on our Computing Help site.

Once we’re confident there are no major issues we intend to replace the two NX services with equivalents based on RDP. The aim being to get the new service entirely rolled out before the start of Semester 1 in September.

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Getting Started With Cloud Printing

Now that every floor in the Forum has at least one cloud printing device with more to follow, I thought it might be useful to provide a few hints and tips on how to get started with cloud printing.

  1. Setting your machine up
    • DICE managed machines
    • You don’t need to do anything, the cloud queues are already installed on the School print servers.

    • OSX
    • We strongly recommend that you install the IS cloud printing package. This can be downloaded here.

    • Windows
    • For managed desktop machines, see here. For other Windows machines, see here.

    • non-DICE Linux
    • See here.

  2. Sending a job to a cloud queue
  3. It is extremely important that you are using the correct drivers when you send a job to a cloud queue. If you have followed the relevant instructions above, this should already be the case. Since the cloud printers use the same drivers as the existing Xerox printers in the School, any options you currently use for the Xerox printers should just work with cloud queues.

    There are two cloud print queues, cloud-mono and cloud-colour. As the names imply, the cloud-mono queue is for jobs which you wish to print in black and white and the cloud-colour queue is for colour jobs. Note that mono documents sent to the colour queue will be charged at the rate for a colour printout.

    Jobs are sent to the cloud queues in exactly the same way as to any other print queue, whether via a shell command such as lpr or an application’s print dialogue box.

  4. Collecting your printout
  5. This may not be a simple matter of walking to the nearest cloud device. Not all cloud devices are created equal and some devices are more capable than others.

    All cloud devices can produce A4 mono printouts. The devices on levels 4 and 9 of Appleton Tower can produce A4 colour prints and the larger colour devices on level 6 of Appleton Tower, the ground floor coffee area of the Wilkie Building and in the NE corners of the Forum can produce A3 and A4 colour and mono printouts. These latter devices are also capable of feats such as collating and stapling printouts. It’s important to remember that if you attempts to print out a job on a device which lacks a desired ability, for instance printing an A3 job on a device which only supports A4, then the job may well disappear from your queue but not actually be printed out! All cloud devices should have a poster nearby detailing their capabilities.

    All cloud devices are capable of colour scanning

    Once you are standing in front of a cloud device with the capabilities you require, hold your University ID card against the card reader, which looks like this:

    after a short period, you will be presented with the following screen:

    NOTE: If you have not used cloud printing before, you may be asked to associate an account with your ID card. Do this by typing your DICE user name and your University AD password into the appropriate boxes. You should only need to do this once. If you don’t know what your AD password is, Support can help

    Most of the options on this screen should be obvious, EveryonePrint is a service which makes it easy to print from mobile devices. More details here

    To release your print jobs, press the button marked Print job release. You will see a screen like this:

    Remember, on a device which can only do mono printouts, you will only see jobs sent to the cloud-mono queue.

    You can select as few or as many jobs as you like. Pressing the Print button will print your jobs out. You can also delete jobs if you’ve changed your mind. Note that jobs are deleted automatically if they are not printed out within 24 hours. You don’t have to stay logged in while the jobs are printing, if you have a lot of printing to do, you can simply set things in motion, log out by pressing the (real) button marked with a key, and come back to pick up your printouts later.

  6. Other things to note
  7. Once a printer has been cloud enabled, you will need to tap in with your card before you can photocopy or scan. A benefit of this is that when scanning, your email address will automatically be set as the destination for the scan.

  8. Trouble Shooting
    • I tried to release a job and it just disappeared!
    • As mentioned above, one flaw in the cloud printing system is that jobs which the printer is incapable of printing may simply disappear. Once way to check if this is happening is to look at how much you are being charged for the job (this information is displayed in the Print Job Release screen). If you aren’t being charged a multiple of 5p for a single sided mono job or 8p for a two sided job, then you are attempting to print something other that A4 mono. We’ve noticed that applications such as Acroread can set the paper size to A3 for no apparent reason. If you have the misfortune to have to pay for your printing and this happens to you, contact support for a refund.

    • I can’t see a Scan button! How do I scan?
    • Somewhat counter-intuitively, the button for scanning is labelled Email

    • I tried following the instructions for installing the cloud queues on a self-managed Windows machine but all I get is an error message saying

      Windows cannot access \\SERVER\printers

      We’re not sure why this is happening but missing out the \printers part should do the trick.

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