[Bug 1541544] Comment bridged from LTC Bugzilla

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------- Comment From ursula.braun at de.ibm.com 2016-02-05 11:40 EDT-------
We have to distinguish between the different device types supported by the qeth driver:
1. OSA-cards: the qeth default is layer2. The OSA-card is able to convert between layer2 and layer3. Thus no lack of connectivity here. Nevertheless a customer may want to select layer3, especially if he wants to make use of TCP Segmentation Offload.
2. HiperSockets: the qeth default is layer3 to allow smooth communication with zOS. HiperSockets LANs are either layer2 or layer3; there is no connectivity between a layer2 participant and a layer3 participant.
3.virtual NICs attached to a z/VM VSWITCH or GuestLAN when Linux is running as a z/VM guest: Here the Linux definition has to follow the layer definition of the VSWITCH or GuestLAN in z/VM, otherwise connectivity is broken. Up to now there is no automatic detection of the layer defined in z/VM.

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https://bugs.launchpad.net/bugs/1541544

Title:
  ubuntu-installer makes a contradictional statement regarding
  layer2/layer3

Status in debian-installer package in Ubuntu:
  New

Bug description:
  == Comment: #0 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2016-02-03 12:05:19 ==
  When I configure a qeth OSA device, the installer asks for device type, device and protocol layer:

  Please choose the type of your primary network interface that you will need for 
   
  installing the Debian system (via NFS or HTTP). Only the listed devices are   
  supported.  
  Network device type:  
    1: ctc: Channel to Channel (CTC) or ESCON connection,      
    2: qeth: OSA-Express in QDIO mode / HiperSockets,      
    3: iucv: Inter-User Communication Vehicle - available for VM guests only,     
   
    4: virtio: KVM VirtIO,      
  Prompt: '?' for help> 2
  2  
    
  Please select the OSA-Express QDIO / HiperSockets device.  
  Device:  
    1: 0.0.f5f0-0.0.f5f1-0.0.f5f2  [*],  
  Prompt: '?' for help, default=1> 1
  1  
    
  By default OSA-Express cards use layer3 mode. In that mode LLC headers are   
  removed from incoming IPv4 packets. Using the card in layer2 mode will make it
  keep the MAC addresses of IPv4 packets.  
  Use this device in layer2 mode?  
    1: Yes [*]  2: No  
  Prompt: '?' for help, default=1> 

  The last question experienced a change according to https://bugs.launchpad.net/ubuntu/+source/s390-netdevice/+bug/1526801
  Layer2 is the default, which is correct, since the qeth driver uses layer2 as default as well.

  However, the introductional text says: "By default OSA-Express cards
  use layer3 mode."

  And this is wrong and needs to be fixed. Correct wording is:

  "By default OSA-Express cards use layer2 mode. In layer3 mode LLC headers are   
  removed from incoming IPv4 packets. Using the card in layer2 mode will make it   
  keep the MAC addresses of IPv4 packets."

  == Comment: #2 - Thorsten Diehl <thorsten.diehl at de.ibm.com> - 2016-02-03 12:08:52 ==
  Although LP 1526801 deals with this subject, it is different.
  LP 1526801 is implemented and closed. Now the documentational part in the installer needs to follow that. Thus I recommend to treat this as a separate bug.

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