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The GRETINA network at ANL

The decomposition cluster is located in g126 and has a 20GBit fiber optics link to area 4 where the digitizer racks are located. There is a 1GBit fiber optics link from g126 to the data room as well. The NAT box that defines private network,, is located in g126. The gretina 10.0.x.x network (private) is separate from onenet.

There are three fiber runs from g126. Two goes to the area4 experimental hall:

 |10GB switch(0)|---------------------|10GB switch(0)|........| NAT|
 |10GB switch(1)|---------------------|10GB switch(1)|........| NAT|
 (digitizers)              ^          (decomposition cluster)
                    Fiber runs 1/2           
                    under the road  

That gives us a 20 GBs link from the digitizers to the decomposition cluster. The third fiber run goes to the ATLAS dataroom for control and is limited to 1GBs

 data room (my switch)                      g126 (GRETINA switch)
 |1GB switch|.....|FMC|---------------------|FMC|.....|10GB switch(a)|
               ^                 ^                 ^
  simple 1GB   |                 |                 |
    switch     cu           Fiber run 2            cu
                         under the road

where FMC denotes Fiber Media Converter (LC to regular RJ45 Gigabit)

Access from outside to the GRETINA network

You can access the the GRETINA private network through the NAT box that defines the private network, You will be port-forwarded to a linux box called 'ws1.gam'. For accounts on this linux box (and thereby access to the GRETINA private network), send an Email to Once you have ssh'ed to this machine, you can ssh from there to any of the other GRETINA nodes. There are no direct outsideIP-to-insideIP connections to other GRETINA nodes as it was done at MSU.

example: user XX want to access the gretina account on a1.gam.

 ssh -X

user gets port forwarded to ws1.gam where the user logs in under his own name. Then the user accesses the gretina account on a1.gam as

 ssh -X gretina@a1.gam

you cannot access the GRETINA network from the outside via the GRETINA account.