Protocol 1 the official procedure or system of rules governing affairs of state or diplomatic occasions : protocol forbids the prince from making any public statement in his defense. • the accepted or established code of procedure or behavior in any group, organization, or situation : what is the protocol at a conference if one's neighbor dozes off during the speeches? • Computing a set of rules governing the exchange or transmission of data electronically between devices. Protocols and Services 2 the original draft of a diplomatic document, esp. of the terms of a treaty agreed to in conference and signed by the parties. • an amendment or addition to a treaty or convention : a protocol to the treaty allowed Dr. Christian Rohner for this Danish referendum. 3 a formal or official record of scientific experimental observations. • a procedure for carrying out a scientific experiment or a course of medical treatment. ORIGIN late Middle English (denoting the original record of an agreement, forming the legal authority for future dealings relating to it): from Old French prothocole , via medieval Latin from Greek protokollon .’ Sense 1 derives from French protocole , the collection of set forms of etiquette to be observed by the French head of state, and the name of the government department responsible for this (in the 19th cent.). Source: Oxford American Dictionary Communications Research Group Protocol: getTime Protocols and Services from_above (what's the time?) ----------------------------------- client send_msg(server, HI) Hi! WAIT_HI IDLE rcv_msg(HI) Hi! --------------------------------- rcv_msg(BYE) send_msg(server, TIME?) --------------------- Service getTime(dest) What's the time? WAIT_DATE WAIT_BYE It's 12:30 rcv_msg(TIME) Protocol ------------------------------- to_above (the time is TIME) Thanks, bye! send_msg(server,BYE) t_struct getTime (dest) { Bye! send_msg(dest, “Hi!”); rcv_msg(); send_msg(dest, “Time?”); t_struct time = rcv_msg(); send_msg(dest, “Bye!”); return time; }
Protocols and Services Protocols and Services getTime(dest) N+1 PDU Layer N+1 N+1 Entity N+1 Entity send_msg(dest) Service Primitive(s) rcv_msg() N PDU Layer N N Entity N Entity Layer N: - Services provided to N+1 - Services expected from N-1 - internal operation (Protocol) OSI Reference Model OSI Reference Model user or server applications 7 - Application 7 - Application syntax and semantics of information 6 - Presentation 6 - Presentation (datastructures, encoding, etc.) dialog control, token management, 5 - Session 5 - Session synchronisation co-ordinates communication “end-to-end” 4 - Transport 4 - Transport multiplexing find a path to the destination 3 - Network 3 - Network forward messages co-ordinates communication on a link. 2 - Link 2 - Link co-ordinates access to the physical layer modulation, transmission, etc. 1 - Physical 1 - Physical
Layering Analogy Layering: Transport Service • Collaboration between two distracted professors • So distracted, they rely on their assistants to keep track "#$% ( ) “Can you please get this paper to Einstein? And let me know "#$% & ' Prof. Tournesol Prof. Einstein what he responds!” "##$#%&'% Source: Matthias Grossglauser, EPFL Source: Matthias Grossglauser, EPFL Layering: Transport Protocol Layering: Network Service • The assistants remember and track the entire • The assistants use the postal service to carry letters exchange during the collaboration back and forth between their offices ck and forth between their offices +,$-(./0(12%(%32(4&425 65/7(85/69(:/05'2#/;(6/5 85/69(<$'#%2$'(%3&% -%%*%&./& '01$23 =(#2'%(./0(;&#%(>22?@A !"#$%&!'$(#)*+$, !-"./ !/0(+0))* "##$#%&'%() "##$#%&'%(* 4$3 "#$%&!-1)+2*1) -'3 4(#156 +B/C(/';.(%32(/'2 #$%&'())*+, 65/7()D(-&.#(&1/9 E&'(./0(#2'-(72 &'/%325(F/4.@A Source: Matthias Grossglauser, EPFL Source: Matthias Grossglauser, EPFL
Layering: Network Protocol Layering: Link Layer Service • Postal service forwards the letter through multiple centers 1,234566(&7 &'() &'() "#$% "123 *+,-+./! *+,-+./0 89$()*43:(2 ;7337$43, 415/6+-/-7(8 </(;4+7)37$4"= )+--+./-5/39.(:7; </,++=/-5 #$%&'()* >5.?'.=/(-/-5 +,-./)0 &'()/*+,-+./0@ Source: Matthias Grossglauser, EPFL Source: Matthias Grossglauser, EPFL Layering: Link Layer Protocol Layering Analogy • Trucking company carries letter to next mail center, where another routing decision is made Profs. Tournesol and Application Einstein’s collaboration Assistants 1+2, keeping track Transport layer: reliable of letters message exchange. #$%&'()*+,-$. #$%&'()*+,-$. /.+0/(1+23).3$+! /.+0/(1+23).3$+4 Post office Network layer: best-effort datagram delivery service Trucking company Link layer Source: Matthias Grossglauser, EPFL Source: Matthias Grossglauser, EPFL
Message Encapsulation Example Network Layer: IP Header Depending on the protocol, the header includes protocol type, addresses, size of the payload, identifier, checksum, etc. Message Application Segment Transport Header Payload Dataframe Network Frame Link Physical The Internet Protocol Stack Multiplexing • A collection of protocols • A system or signal involving simultaneous transmission • Concentration at the Network Layer of several messages along a single channel of communication. future: will everything have an IP address? • Several applications access the network simultaneously: Use transport layer port numbers to Application Mail WWW IM P2P ... distinguish them. Transport TCP UDP Mail WWW IM ??? Network IP TCP UDP ??? Link IP Ethernet WiFi Bluetooth 3G ... Physical incoming message
Well-Known Port Numbers (0..1023) www.iana.org/assignments/port-numbers (IANA: coordination) /etc/services (extract) echo 7/udp # Echo ftp-data 20/tcp # File Transfer [Default Data] ftp 21/udp # File Transfer [Control] ssh 22/tcp # SSH Remote Login Protocol smtp 25/tcp # Simple Mail Transfer time 37/udp # Time name 42/udp nameserver # Host Name Server http 80/tcp www www-http # World Wide Web HTTP pop3 110/tcp # Post Office Protocol - Version 3 ntp 123/udp # Network Time Protocol snmp 161/udp # SNMP https 443/tcp # http protocol over TLS/SSL
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