Flashcards
File Access
Cards in this deck (15)
- 1Two basic online file-sharing paradigmsWhole-file copying
Piecewise file access - 2Piecewise access mechanismsOpaque
Transparent - 3Opaqueapplication uses special facilities to access remote file
- 4Transparentapplication uses special facilities to access local and remote files
- 5Whole File CopyingClient: contacts server, specifies file, specifies transfer direction
Server: maintains set of files on local disk, waits for contact, honors request from client - 6File Transfer Protocol (FTP)Major TCP/IP protocol for whole-file copying
Uses TCP for transport - 7Features of FTPInteractive access
Format specification (ASCII or EBCDIC)
Authentication control (login and password) - 8FTP's use of TCPData transfer connections and the data transfer processes that use them can be created dynamically when needed, but the control connection persists throughout a session. Once the control connection disappears, the session is terminated and the software at both ends terminates all data transfer processes.
- 9Secure Sockets Layer FTP (SSL-FTP)Uses secure sockets layer technology
All transfers are confidential - 10Secure File Transfer Program (sftp)Almost nothing in common with FTP
Uses ssh tunnel - 11Secure Copy (scp)Derivative of Unix remote copy (rcp)
Uses ssh tunnel - 12Trivial File Transfer Protocol (TFTP)Alternative to FTP
Whole-file copying
Not as much functionality as FTP
Code is much smaller
Intended for use on LANs
Runs over UDP
Diskless machine can use to obtain image at bootstrap - 13TFTP RetransmissionSymmetric (both sides implement timeout and retransmission)
Data block is request for ACK
ACK is request for next data block - 14Sorcerer's Apprentice BugConsequence of symmetric retransmission
Duplicate packet is perceived as second request, which generates another transmission
Duplicate response triggers duplicate packets from the other end - 15Network File System (NFS)Protocol for file access, not copying
Developed by Sun Microsystems, now part of TCP/IP standards
Transparent (application cannot tell that file is remote)
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- Networks Flashcards on File Access, created by M KB on 05/11/2018.
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- M KB
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