(a) Dorm floor: A multi-access bus network such as Ethernet
(b) University: A ring network or a hierarchical tree structure
(c) State: A partially connected network (since this is a wide area network).
(d) State: A partially connected network (since this is a wide area network).
Although UDP does not have the connection setup and tear down overheads of TCP,
it is not suitable for HTTP since it does not provide a reliable service (i.e., packets can
get lost in the network). TCP automatically recovers lost packets using re-transmissions.
One could improve the performance of HTTP by using a single connection to download multiple
objects from the server (instead of setting up a separate connection for each item that
needs to be downloaded). This amortizes the connection setup and tear down cost of HTTP
across multiple items.
(i) Data migration: fetch file from a remote machine to a local machine when an
application needs to access it.
(ii) Computation migration: Move the computation to the data; useful
when moving the computation is cheaper than moving data.
(iii) Job migration: Move the job and execute the remaining portion of it
on another machine. This causes both data and computations to move to than machine
Location transparency: the name of the file does not reveal its physical storage
location.
NSF is location transparent, since each remote file has a local name which does not reveal
its location. It is also location independent, so long as the mount table is adjusted to
reflect the new location of the file on the server.
Location independence: The name of the file is independent of its storage location
(and hence, does not change if the file location changes.