Microsoft PowerPoint - 13_appl.ppt

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승아 아
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1 최양희서울대학교컴퓨터공학부

2 Telnet File Transfer (FTP) (SMTP) Web (HTTP) Internet Telephony (SIP/SDP) Presence Multimedia (Audio/Video Broadcasting, AoD/VoD) Network Management (SNMP) 2005 Yanghee Choi 2

3 Remote terminal protocol running over TCP connection Keystrokes are passed transparently to the server Network Virtual Terminal (NVT) user s I/O device Client System Format Used client NVT Format Used server Server System Format Used server s system 2005 Yanghee Choi 3

4 To pass control functions, escape sequence is used IAC (interpret next octet as command) Command interrupt is transferred via out-of-band signal (TCP Urgent Data) 2005 Yanghee Choi 4

5 Interactive file access over TCP Format Specification : FTP allows the client to specify the type and format of the stored data Authentication control : login name and password rfc959 (Oct. 1985) 2005 Yanghee Choi 5

6 control connection persists throughout the session. data connections can be created dynamically when needed. client server data transfer control process control process data transfer randomly chosen port control connection well known port 21 well known port 20 data connection INTERNET 2005 Yanghee Choi 6

7 Trivial File Transfer Protocol over UDP Timeout, Retransmission - symmetric (sender/receiver) Fixed size (512 octets) blocks Stop-and-wait (ACK for every block) READ, WRITE, DATA, ACK, ERROR 2005 Yanghee Choi 7

8 mail exchange between mailboxes spooling at the sender periodic check of spool area for undelivered mail (30 min typical) mail returned to the sender if undeliverable after an extended time (3 days typical) direct, end-to-end delivery or mail gateway sender - client receiver - server over TCP 2005 Yanghee Choi 8

9 alias database user sends mail user alias expansion and forwarding outgoing mail spool area mail client (background transfer) user reads mail interface mailbox for incoming mail server (to accept mail) TCP connection 2005 Yanghee Choi 9

10 mail destination machine name, mailbox address can be different with domain name, and user login name DNS is used to get mail exchanger information Format - RFC 822 Protocol - SMTP (Simple Mail Transfer Protocol) RFC 821 MIME (Multipurpose Internet Mail Extensions) RFC 2045, 2046, Yanghee Choi 10

11 Sender deletes message after confirming the delivery to the server : direct end-to-end delivery is reliable For security, interoperability, mail gateway is often used 2005 Yanghee Choi 11

12 Simple Mail Transfer Protocol ASCII text oriented header is separated from body by a blank line 2005 Yanghee Choi 12

13 Short messages (less than 1000 characters per line, 7-bit ASCII) Conversion from non-textual data to 7-bit ASCII 2005 Yanghee Choi 13

14 POP3 (Post Office Protocol) IMAP4 (Internet Message Access Protocol) 2005 Yanghee Choi 14

15 allows arbitrary data to be encoded in ASCII and transmitted in a standard message MIME version, content-type, encoding used to convert the data to ASCII are included in MIME header multipart message - parts are separated by -- StartOfNextPart 2005 Yanghee Choi 15

16 Text image audio video application multipart message plain, enriched JPEG, gif basic (PCM) MPEG octet-stream, PostScript an encapsulated message (rfc822, partial, external-body) 2005 Yanghee Choi 16

17 Mixed alternative parallel digest mixed set of parts representing the same data in multiple formats to be viewed simultaneously each part has a default type of message/rfc Yanghee Choi 17

18 World Wide Web Hypermedia document between web browser and web server HTML (HyperText Markup Language) anchor URL (Uniform Resource Locator) HTTP (HyperText Transfer Protocol) 2005 Yanghee Choi 18

19 Application level (over TCP) Request/response GET HTTP/1.1 Stateless Bidirectional transfer Capability negotiation Support for caching Support for intermediaries 2005 Yanghee Choi 19

20 2005 Yanghee Choi 20

21 Persistent Connections instead of using a TCP connection for each transfer, a persistent connection approach is adopted as default in HTTP 1.1 reduced overhead pipelining requests need to identify the beginning and end of each item : sending a length followed by an item of that size 2005 Yanghee Choi 21

22 Proxy server Caching 2005 Yanghee Choi 22

23 transport protocol for realtime applications end-to-end delivery service payload type identification sequence numbering timestamping delivery monitoring runs on top of UDP (multiplexing, checksum) supports multicast, if provided by underlying network does not address resource reservation and does not guarantee QOS for real-time services (low layers do that) 2005 Yanghee Choi 23

24 RTP carry data with realtime properties application level framing and integrated layer processing require a profile specification document and payload format specification documents designed to be independent of the underlying network and transport layers RTCP (RTP Control Protocol) RTP control protocol monitor QoS convey information about the participants in an ongoing session 2005 Yanghee Choi 24

25 V P X CC M PT sequence number timestamp SSRC ID CSRC IDs... version (V) : 2 padding (P) : extension (X) : extension header CSRC count (CC) : number of CSRC identifiers following the header marker (M) : defined by a profile payload type (PT) : sequence number : increment by one for each RTP data packet timestamp : allow synchronization and jitter calculation SSRC ID : CSRC IDs : 2005 Yanghee Choi 25

26 Each medium (audio, video) should be carried in a separate RTP session with its own destination transport address (network address + port number) 2005 Yanghee Choi 26

27 periodic transmission of control packets to all participants in the session providing feedback on the quality of the data distribution flow and congestion control carrying a persistent transport-level ID for an RTP source (CNAME) controlling the rate of RTCP packets convey minimal session control information (ex. Participant identification in the user interface) : optional 2005 Yanghee Choi 27

28 RTCP packet types SR : sender report RR : receiver report SDES : source description items BYE : indicates end of participation APP : application specific functions Multiple RTCP packets may be... concatenated in a single packet of the lower layer protocol, for example UDP 2005 Yanghee Choi 28

29 RTCP Transmission Interval RTP is designed to scale from a few participants to thousands, therefore the transmission rate must be scaled down Calculation of RTCP transmission interval session bandwidth is reserved RTCP if fixed at 5% of session bandwidth the allowed control traffic bandwidth is divided among participants 2005 Yanghee Choi 29

30 H.323 : ITU SIP (Session Initiation Protocol) : IETF 2005 Yanghee Choi 30

31 SIP (Session Initiation Protocol) Defined in RFC 3261 Manages real-time sessions over IP data network Intended to enable Internet telephony/voip Based on HTTP-like request/response transaction model Five facets User location User availability User capabilities Session setup Session management 2005 Yanghee Choi 31

32 Client/server elements Client sends/receives SIP messages Includes user agents, proxies Network elements User agent (client/uac, server/uas) Redirect server Proxy server Registrar Location service 2005 Yanghee Choi 32

33 2005 Yanghee Choi 33

34 2005 Yanghee Choi 34

35 Request Methods REGISTER INVITE ACK CANCEL BYE OPTIONS Response Types Provisional (1xx) Success (2xx) Redirection (3xx) Client Error (4xx) Server Error (5xx) Global Failure (6xx) 2005 Yanghee Choi 35

36 SDP (Session Description Protocol) Media Streams Addresses Ports Payload types Start and stop times Originator 2005 Yanghee Choi 36

37 2005 Yanghee Choi 37

38 application level protocol every router should understand the same protocol manager s host = client : management agent routers = servers : server program Authentication mechanism is required 2005 Yanghee Choi 38

39 Simple Network Management Protocol MIB (Management Information Base) maintained at each host/router about the resource status SMI (structure of management information) - rules to define and identify MIB variables ASN.1 (abstract syntax notation one) - formal notation to define names and types for variables in MIB MIB variables names are taken form the object identifier namespace administered by ISO/ITU 2005 Yanghee Choi 39

40 system interfaces addr. trans. ip icmp tcp udp egp The host or router OS individual network interfaces address translation (e.g. ARP mappings) IP software ICMP software TCP software UDP software EGP software 2005 Yanghee Choi 40

41 sysuptime system Time since last reboot ifnumber interfaces # of network I/F ifmtu interfaces MTU for a particular I/F ipdefaultttlip TTL value used in IP ipinreceives ip # of datagrams received icmpinechoes icmp # of ICMP Echo Req recd tcpmaxconn tcp Max TCP connections allowed 2005 Yanghee Choi 41

42 get-request get-next-request get-response set-request trap Fetch a value from a specific variable Reply to fetch operation Store a value in a specific variable Reply triggered by an event FETCH - STORE Paradigm is used 2005 Yanghee Choi 42

TCP.IP.ppt

TCP.IP.ppt TCP/IP TCP/IP TCP/IP TCP/IP TCP/IP Internet Protocol _ IP Address Internet Protocol _ Subnet Mask Internet Protocol _ ARP(Address Resolution Protocol) Internet Protocol _ RARP(Reverse Address Resolution