2 Chapter 2. Cabling Blue Gene/L You need to externally provide cabling for four separate functions on a Blue Gene/L system. As you can imagine, for systems with a large number of racks, this is no trivial task. The data (also called the torus ) network carries information between the compute nodes in the system. The service network acts as a bridge between each of the midplanes and the service node. This network carries instructions that are sent to the various pieces of hardware. The clocks on each of the service cards also need to be cabled together to synchronize the processors. The functional network carries data from the I/O nodes to the control system and the file servers. © Copyright IBM Corp. 2007. All rights reserved. 23