Comparative Security of NFS and AFS

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Comparative Security of NFS and AFS

FEATURE                         NETWORK FILE SYSTEM


ARCHITECTURAL MODEL             Client/server; each file server
                                managed independently


SECURITY MECHANISMS             Based on unencrypted user IDs,
                                trusted users, and hosts


SECURITY DURING                 Users lose access to files during
RECONFIGURATION                 reconfiguration; file-system moves
                                require changes to mount point


SECURITY ADMINISTRATION         Only system administrator can set up
                                and maintain protection groups--sets
                                of users with common access rights

                                to specific groups of files


ACCESS CONTROL                  Uses standard Unix chmod command and
                                mode bits on files and directories; offers
                                only read, write, and execute rights to
                                files and directories


AVAILABILITY                    No standard data replication


INTEGRATION WITH KERBEROS       Possible, but difficult


BACKUP                          Standard Unix backup; file system
                                inactive during backup; no cloning means
                                system administrator must perform all
                                restores; can use cachefs


FILE CACHING IN LOCAL STORAGE   Constant caching of file attributes slows
                                performance on WANs


FEATURE                         ANDREW FILE SYSTEM


ARCHITECTURAL MODEL             Truly distributed; administration by
 
                                cell--file servers and clients that
                                form a logical administrative unit


SECURITY MECHANISMS             Kerberos authentication; 
                                Authentication Server process, 
                                Protection Server process


SECURITY DURING                 Reconfiguration doesn't affect users; 
RECONFIGURATION                 files are accessible during moves, and
                                filenames don't change


SECURITY ADMINISTRATION         Users can create groups


ACCESS CONTROL                  Access-control lists allow fine control
                                granularity by groups and individuals;
                                supports read, lookup, insert, delete,
                                write, lock, and administration rights;
                                applied by directory only


AVAILABILITY                    Read-only replication per volume allows

                                users to access a different replica
                                in the event of a server crash


INTEGRATION WITH KERBEROS       Integrates tightly


BACKUP                          No system downtime during backup 
                                with AFS Backup Server; volume clones
                                allow limited user-controlled restores


FILE CACHING IN LOCAL STORAGE   Automatic notification 
                                of file changes cuts unnecessary
                                network traffic
Source: Transarc Corp.