FTS Channels

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The FTS has a management concept of network channels.

Channels are point to point connections between domains (e.g., ed.ac.uk to rl.ac.uk). When a job is submitted, if the SURLs to be copied match the domains of a channel then the job is allocated to that channel.

Each channel has a nominal bandwidth and a maximum concurrent transfer number. Each channel can be independently controlled, i.e., started, stopped, drained, etc. This allows for very useful control of data flows between particular domains, independent of any other data transfers.

Note that these channels are a concept held only within the FTS itself, so the actual lower level routing between SRMs will happen according to the routing tables and network infrastructure at a site, thus channels may share network connections for part of their path.

Within LCG channels are particularly useful given well defined data flows expected from the LHC, where channels are defined from the Tier 0 (CERN) to each Tier 1 (e.g., RAL); then from each Tier 1 to regional Tier 2 sites.

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Note that channels, in LCG, are "owned" by the upper tier, so files are "pushed down" and "pulled up".

In the UK RAL Tier1 run the RAL Tier1 File Transfer Service, which defines channels between RAL and each of the Tier 2s.