Server channel rules

This information is used with the following rules. First, some nomenclature:

• FG - foreground
• BG - background
• station (?) - multicast channel over which a set of pages is shared
• lineup (?) - set of pages with shared usage properties
• directory - mcast channel over which stations are announced

1. a FG GET is generated when all proxies on the path from client to server fail to 'hit' on a request

   at this point, one of three cases applies:

   1. a request IS in the lineup
      AND client IS tuned to the station of that lineup
      AND response HAS NOT recently been sent on that station

      There are two different ways to handle this. The first relies on the mcast channel to send the response to the request, which could be problematic (requires FG mcast):

      • stall the response to the GET until mcast finishes
      • mcast a FG response to the station
      • respond to the GET with a REDIRECT (Amy's hack)

      The second variant is the same as the next case, having the advantage of using only BG mcast:

      • unicast a FG response to the client
      • mcast a BG response to the station

   2. a request IS in the lineup
      AND client IS NOT tuned to the station of that lineup
      AND response HAS NOT recently been sent on that station
      • unicast a FG response to the client
      • mcast a BG response to the station

   3. ALL OTHER CASES, i.e.,
      if response IS NOT tuned to the station of that lineup
      OR response HAS recently been sent on that station
      • unicast a FG response to the client

2. a BG GET is generated when exactly one intermediate proxy decides, in which case:
   1. if response IS in the lineup
      AND client IS tuned to the station of that lineup
      AND response HAS NOT been recently sent to the mcast channel
      • mcast a BG response to the channel

   2. ELSE
      • unicast a BG response to the client

Page maintainer: the LSAM project