COMPUTER NETWORKS Protocol architectures

Transcription

1 OMPUTR NTWORKS Protocol architectures Protocol architectures ruppo Reti TL rchitectures and protocols TT definition ommunication: transfer of information according to pre-established conventions ommunication requires cooperation One abstract description of the communication paradigm between two or more s requires the definition of a reference model t the maximum level of abstraction, the reference model specifies a network architecture OMPUTR NTWORKS Protocol architectures - 1 OMPUTR NTWORKS Protocol architectures - 2 Protocol architectures network architecture defines the objects used to describe the communication process the relation among such objects the functionalities to support the communication the structure of the functions Layered architectures are used because of simple design simple management simple standardization separation among functions OMPUTR NTWORKS Protocol architectures - 3 host 3 Separation among functions: nternet host 4 subnet 4 subnet 1 router 1 router 2 subnet 3 host 2 router 3 host 1 subnet 2 applications error control routing packet transfer OMPUTR NTWORKS Protocol architectures - 4 Open System nterconnection OS Layered architectures pplication Presentation Session Transport ata link pplication Presentation Session Transport ata Link OS User Netw. ppl. Session nd to nd Routing ata Link NT pplication nternetwork RP Transaction Presentation ata low Manag. Trans. ontrol Virtual Route xplicit Route Transm. roup ata Link SN half session path control OMPUTR NTWORKS Protocol architectures - 5 OMPUTR NTWORKS Protocol architectures - 6 Pag. 1

2 OMPUTR NTWORKS Protocol architectures OS and nternet - SN OS nternet Protocol Suite pplication Presentation Telnet TP SMTP NS XR Management plane ontrol plane User plane Plane management Layer management Session SNMP RP igh layers igh layers Transport ata link MP RP e RRP TP e UP P Routing protocols L TM Unspecified OMPUTR NTWORKS Protocol architectures - 7 OMPUTR NTWORKS Protocol architectures - 8 Protocols TT definition formal definition of the procedures adopted to guarantee the communication between two or more objects on the same hierarchical level Protocol definition: semantics set of commands and answers syntax structure of commands and answers timing temporal sequence of commands and answers OMPUTR NTWORKS Protocol architectures - 9 Protocols are set of semantic rules algorithms syntactic rules formats timing Protocols OMPUTR NTWORKS Protocol architectures - 10 SO/OS model OS model (Open System nterconnection) defined in the following standards SO S 7498 TT X.200 The fundamental principles defined in the OS model are universally accepted this does not mean that all the protocol architectures conform to OS model System 3 System1 System j Transmission media System 2 System n OMPUTR NTWORKS Protocol architectures - 11 OMPUTR NTWORKS Protocol architectures - 12 Pag. 2

3 OMPUTR NTWORKS Protocol architectures OS model Layers (or levels) System System System System igher layer System System pplication process Transmission media (N+1) - layer (N-1) - layer Lower layer subsystem transmission media OMPUTR NTWORKS Protocol architectures - 13 OMPUTR NTWORKS Protocol architectures - 14 ntities Layering active elements in a subsystem run the functions of the layer interact within the same layer System transmission media System OMPUTR NTWORKS Protocol architectures - 15 ach layer (or level) provides services to the higher layer using the services from the lower layer its own functionalities an be identified: service provider service SP ( ccess Point) OMPUTR NTWORKS Protocol architectures - 16 (N+1) - layer s The s at layer N and the (N+1) - entities cooperate and communicate using the (N) service offered by the (N) service provider uses provides (N) - service s service can be: connection-oriented (O): a preliminary agreement (connection) is established between the network and the communication end-points, then the data is transferred and finally the connection is released connectionless (L): data is sent to the network without any preliminary agreement and is treated independently from each other OMPUTR NTWORKS Protocol architectures - 17 OMPUTR NTWORKS Protocol architectures - 18 Pag. 3

4 OMPUTR NTWORKS Protocol architectures s s (N) - service (N-1) - service N+1 N+1 N N N (N) service provider N N-1 (N-1) service provider N-1 lack-box for the lack-box for the OMPUTR NTWORKS Protocol architectures - 19 OMPUTR NTWORKS Protocol architectures - 20 SP ( ccess Point) ach (N-1)-SP is associated with at most one (N)-entity Protocols System System (N-1) - SP (N+1) - protocol (N) - servizio (N) - SP (N) - protocol (N-1) - entity (N-1) - entity (N-1) - layer OMPUTR NTWORKS Protocol architectures - 21 OMPUTR NTWORKS Protocol architectures - 22 ddressing unctions for identification (N) - title ddress translation (N) directory (N-1) - SP (N-1) - address (N-1) - layer (N-1) - address (N) - title (N-1) - entity OMPUTR NTWORKS Protocol architectures - 23 OMPUTR NTWORKS Protocol architectures - 24 Pag. 4

5 OMPUTR NTWORKS Protocol architectures unctions for identification Possible mappings ddress translation (N) - mapping (N) - address K L M (N) - SP K K L M (N-1) - SP (N-1) - address one-to-one hierarchical tabular OMPUTR NTWORKS Protocol architectures - 25 OMPUTR NTWORKS Protocol architectures - 26 onnections onnections (N-1) - SP (N-1) - SP (N-1) - layer (N-1) - layer (N-1) - connections OMPUTR NTWORKS Protocol architectures - 27 connection one-to-many connections one-to-one OMPUTR NTWORKS Protocol architectures - 28 onnections onnections (N-1) - SP (N-1) - SP (N-1) - P (N-1) - layer (N-1) - layer (N-1) - P OMPUTR NTWORKS Protocol architectures - 29 P= onnection nd Point id=identifier (N-1) - P.id OMPUTR NTWORKS Protocol architectures - 30 Pag. 5

6 OMPUTR NTWORKS Protocol architectures greement greement among three possible elements The three elements greement n the case of information transfer without connection, it is sufficient an agreement among two elements The two elements The two elements (N + 1) - entità The two elements (N) service provider (N) (N) service - fornitore provider di servizio OMPUTR NTWORKS Protocol architectures - 31 OMPUTR NTWORKS Protocol architectures - 32 greement n the case of information transfer with connection, it is necessary an agreement among the three elements The three elements (N+1) - layer onnections multiplexing of (N) connections into one (N-1) - connection (N) - SP (N) - P (N) - fornitore service di provider servizio OMPUTR NTWORKS Protocol architectures - 33 OMPUTR NTWORKS Protocol architectures - 34 onnections subdivision of one (N) connection in many (N-1) - connections (N) - P (N) - SP interface (N-1) - layer PU creation (N) - PU (N-1) - SU SP (N-1) - P (N-1) - SU (N-1) - PU OMPUTR NTWORKS Protocol architectures - 35 OMPUTR NTWORKS Protocol architectures - 36 Pag. 6

7 OMPUTR NTWORKS Protocol architectures PU creation On data units, there exists the possibility of segmentation concatenation Segmentation can occur either by building many (N) - PU from one (N) SU or by building many (N-1) - SU from one (N) - PU Similarly for the concatenation nformation transfer System System System System transmission media information path OMPUTR NTWORKS Protocol architectures - 37 OMPUTR NTWORKS Protocol architectures - 38 nformation transfer Primitives Transmitter Receiver (N) - service (N) - service pplication Presentation Session Transport ata link data P SU PP PSU SP SSU TP TSU NP NSU LP LSU bit or symbols pplication Presentation Session Transport ata link RQUST (N) - SP ONRM NTON (N) - SP (N) - protocol (N) service provider NSWR (N+1) - layer OMPUTR NTWORKS Protocol architectures - 39 OMPUTR NTWORKS Protocol architectures - 40 Primitives set of interactions on an interface, occurring in different times and offering a service : service of mail transfer in the postal system eposit of the letter in the mailbox by the sender elivery of the letter into receiver s mailbox by the postman Similar to a procedure Use of primitives Request primitive onfirm primitive cknowledged service provider ndication primitive nswer primitive OMPUTR NTWORKS Protocol architectures - 41 OMPUTR NTWORKS Protocol architectures - 42 Pag. 7

8 OMPUTR NTWORKS Protocol architectures Use of primitives Un-acknowledged service Use of primitives started from the provider Request primitive provider ndication primitive ndication primitive provider ndication primitive OMPUTR NTWORKS Protocol architectures - 43 OMPUTR NTWORKS Protocol architectures - 44 Use of primitives To open a connection To transfer data Use of primitives (N) - ONNT RQUST (N) service provider (N) - ONNT (N) - T RQUST (N) service provider (N) - T NTON NTON (N) - ONNT (N) - ONNT ONRM RSPONS (N) - SP (N) - SP (N) - SP (N) - SP OMPUTR NTWORKS Protocol architectures - 45 OMPUTR NTWORKS Protocol architectures - 46 Use of primitives The seven OS layers To close a connection started from the application pplication protocol application (N) - SONNT RQUST (N) service provider (N) - SONNT NTON presentation session transport network Presentation protocol Session protocol Transport protocol protocol presentation session transport network (N) - SP (N) - SP data link physical ata link protocol layer protocol data link physical transmission media OMPUTR NTWORKS Protocol architectures - 47 OMPUTR NTWORKS Protocol architectures - 48 Pag. 8

9 OMPUTR NTWORKS Protocol architectures Systems Public networks terminal system relay system TRMNL S. RLY SYSTM TRMNL S. layers protocols pplication Presentation Session Transport ata link ata link pplication Presentation Session Transport ata link transfer layers terminal equipement access protocols transfer layers access node network protocols transfer layers transit node transmission media access network internal network OMPUTR NTWORKS Protocol architectures - 49 OMPUTR NTWORKS Protocol architectures - 50 Layer 1: physical layer: provides the mechanical, physical, functional and procedural means, to activate, maintain and disable the physical connections allows to transfer binary digits exchanged among the data link entities data units are bits or symbols defines transmission codes, connectors, voltage levels, etc. Layer 2: data link ata link layer provides the functional and procedural means to transfer data units among network entities handle malfunctions and failures at physical level main functions: error detection and error correction for the transmission flow control data unit delimitation OMPUTR NTWORKS Protocol architectures - 51 OMPUTR NTWORKS Protocol architectures - 52 Layer 3: network layer provides the means to setup, maintain and close the connections among the entities at transport level provides the functional and procedural means to exchange the information among entities at transport level main functions routing flow control and congestion control pricing OMPUTR NTWORKS Protocol architectures - 53 Layer 4: transport Transport layer provides the connections at transport level to the entities at session level compensates the possible lack of quality of service in the connections at network level optimizes the use of the network layer main functions error control control of sequence flow control OMPUTR NTWORKS Protocol architectures - 54 Pag. 9

10 OMPUTR NTWORKS Protocol architectures Layer 4: transport lower layer with end-to-end meaning provides multiplexing and subdivision of the connections allows the fragmentation of messages in packets and their reassembly Layer 5: session Session layer provides one session connection to the entities at presentation layer organizes the communication among entities at presentation level provides the structure and synchronize the data exchange to allow suspending, recovering and terminating masks the interruptions at service level OMPUTR NTWORKS Protocol architectures - 55 OMPUTR NTWORKS Protocol architectures - 56 Layer 6: presentation Presentation layer solves the compatibility issues regarding the data formats solves the issues of data syntax translation may provide services of data encryption Layer 7: application pplication layer provides the application processes with the means to access the OS environment s of service file transfer - TM virtual terminal - VT - X.400 OMPUTR NTWORKS Protocol architectures - 57 OMPUTR NTWORKS Protocol architectures - 58 Trivial network ssume that one (4) entity must communicate with one remote (4) entity We will follow, step-by-step: primitives SUs PUs U 1 N 1 U 2 OMPUTR NTWORKS Protocol architectures - 59 OMPUTR NTWORKS Protocol architectures - 60 Pag. 10

11 OMPUTR NTWORKS Protocol architectures U 1 N 1 U 2 layer 3 service with connection layer 2 service connectionless layer 1 service connectionless OMPUTR NTWORKS Protocol architectures - 61 OMPUTR NTWORKS Protocol architectures - 62 irectory X,, N-ONNT.request(,,...) OMPUTR NTWORKS Protocol architectures - 63 OMPUTR NTWORKS Protocol architectures - 64 N-PU(,, Vid, call request,...) Routing,, Z OMPUTR NTWORKS Protocol architectures - 65 OMPUTR NTWORKS Protocol architectures - 66 Pag. 11

12 OMPUTR NTWORKS Protocol architectures Mapping, Z, L-T.request(,, L-SU,...) OMPUTR NTWORKS Protocol architectures - 67 OMPUTR NTWORKS Protocol architectures - 68 L-PU(,, L-SU, L-P) Mapping,, OMPUTR NTWORKS Protocol architectures - 69 OMPUTR NTWORKS Protocol architectures - 70 P-T.request(,, symbol) OMPUTR NTWORKS Protocol architectures - 71 OMPUTR NTWORKS Protocol architectures - 72 Pag. 12

13 OMPUTR NTWORKS Protocol architectures P-T.indication(,, symbol) L-PU(,, L-SU, L-P) OMPUTR NTWORKS Protocol architectures - 73 OMPUTR NTWORKS Protocol architectures - 74 L-T.indication(,, L-SU,...) N-PU(,, Vid, call request,...) OMPUTR NTWORKS Protocol architectures - 75 OMPUTR NTWORKS Protocol architectures - 76 Routing, Z, Mapping Z,, OMPUTR NTWORKS Protocol architectures - 77 OMPUTR NTWORKS Protocol architectures - 78 Pag. 13

14 OMPUTR NTWORKS Protocol architectures N-PU(,, Vid, incoming call,...) L-T.request(,, L-SU,...) OMPUTR NTWORKS Protocol architectures - 79 OMPUTR NTWORKS Protocol architectures - 80 L-PU(,, L-SU, L-P) Mapping,, OMPUTR NTWORKS Protocol architectures - 81 OMPUTR NTWORKS Protocol architectures - 82 P-T.request(,, symbol) OMPUTR NTWORKS Protocol architectures - 83 OMPUTR NTWORKS Protocol architectures - 84 Pag. 14

15 OMPUTR NTWORKS Protocol architectures P-T.indication(,, symbol) L-PU(,, L-SU, L-P) OMPUTR NTWORKS Protocol architectures - 85 OMPUTR NTWORKS Protocol architectures - 86 L-T.indication(,, L-SU,...) N-PU(,, Vid, incoming call,...) OMPUTR NTWORKS Protocol architectures - 87 OMPUTR NTWORKS Protocol architectures - 88 N-ONNT.indication(,, P.id,...) N-ONNT.response(P.id,...) OMPUTR NTWORKS Protocol architectures - 89 OMPUTR NTWORKS Protocol architectures - 90 Pag. 15

16 OMPUTR NTWORKS Protocol architectures N-PU(,, Vid, call accepted,...) N-PU(,, Vid, call accepted,...) OMPUTR NTWORKS Protocol architectures - 91 OMPUTR NTWORKS Protocol architectures - 92 N-PU(,, Vid, call connected,...) N-PU(,, Vid, call connected,...) OMPUTR NTWORKS Protocol architectures - 93 OMPUTR NTWORKS Protocol architectures - 94 N-ONNT.confirm(,, P.id,...) T-PU(T-P, T-SU) OMPUTR NTWORKS Protocol architectures - 95 OMPUTR NTWORKS Protocol architectures - 96 Pag. 16

17 OMPUTR NTWORKS Protocol architectures N-T.request(P.id, N-SU,...) N-T.indication(P.id, N-SU,...) OMPUTR NTWORKS Protocol architectures - 97 OMPUTR NTWORKS Protocol architectures - 98 T-PU(T-P, T-SU) N-SONNT.request(P.id ) OMPUTR NTWORKS Protocol architectures - 99 OMPUTR NTWORKS Protocol architectures N-SONNT.indication(P.id ) OMPUTR NTWORKS Protocol architectures Pag. 17