1. 18. Mar. 20041INF-3190: Transport Layer Transport Layer Foreleser: Carsten Griwodz Email: griff@ifi.uio.nogriff@ifi.uio.no

2. 18. Mar. 20042INF-3190: Transport Layer Transport service

3. 18. Mar. 2004 3INF-3190: Transport Layer Transport Layer Function To provide data transport Reliably Efficiently At low-cost For Process-to-process (applications) I.e. at endsystem-to-endsystem If possible independent from particularities of the networks used

4. 18. Mar. 2004 4INF-3190: Transport Layer Transport Service Connection oriented service 3 phases connection set-up data transfer disconnect Connectionless service Transfer of isolated units Realization: transport entity Software and/or hardware Software part usually contained within the kernel (process, library) 1-2 3 4 5 Application Layer Transport Entity Network Layer Application Layer Transport Entity Network Layer Service Interface Transport Protocol Service Access Point IP: Message ISO: Transport Protocol Data Unit

5. 18. Mar. 2004 5INF-3190: Transport Layer Transport Protocols & Network Services Transport layer protocol depends on the quality of the network layer service ISO Network type A Network is reliable Network recognizes data loss as an error Errors are displayed to the user i.e. acceptable rate of the errors Minor (for the user acceptable) error rate Network never duplicates or manipulates packets Order of sent packets is always maintained Typically connection oriented network service (CONS) on LANs ISO Network type B Like type A, except Remaining error rate (for data loss) is not acceptable Typically CONS on (old) WANs ISO Network type C Network is unreliable Errors due to losses, duplication and manipulation of packets, as well as faulty packet sequence errors possible Errors might remain undetected Transport protocol has to / should compensate for this Typically connectionless network service (CNLS) on WANs

6. 18. Mar. 2004 6INF-3190: Transport Layer Transport Service Similar services of Network layer and transport layer Why 2 Layers? Network service Not to be self-governed or influenced by the user Independent from application & user enables compatibility between applications Provides for example “only” connection oriented communications or “only” unreliable data transfer Transport service To improve the Network Service Quality Users and layers want to get from the network layer, e.g. reliable service necessary time guarantees

7. 18. Mar. 2004 7INF-3190: Transport Layer Transport Service Transport layer Isolates upper layers from technology, design and imperfections of subnet Traditionally distinction made between Layers 1 – 4 transport service provider Layers above 4 transport service user Transport layer has key role Major boundary between provider and user of reliable data transmission service

8. 18. Mar. 2004 8INF-3190: Transport Layer Transport Service: Terminology Entities exchanged ISO: Transport Protocol Data Unit (TPDU) IP: Message Nesting of messages, packets, and frames Layer Transport Network Data link Physical Data Unit Message or TPDU Packet Frame Bit/byte (bitstream) Message Payload Packet Payload Frame Payload Message header Packet header Frame header

9. 18. Mar. 2004 9INF-3190: Transport Layer Transport protocols ISO defines 5 classes: ISO OSI TP0..TP4 Protocol class Network type Network propertiesName TP0AAcceptable error rate Acceptable rate of displayed errors Simple class TP2Multiplexing class TP1BInacceptable error rate Acceptable rate of displayed errors Basic error recovery TP3Error recover and multiplexing class TP4CInacceptable error rate Inacceptable rate of displayed errors Error recover and multiplexing class

10. 18. Mar. 2004 10INF-3190: Transport Layer Transport Protocols Class TP 0: simple class Mechanisms for connect and disconnect Segmentation / reassembly No error, sequence or flow control No expedited data Class TP 2: multiplexing class Class 0 including additional multiplexing capability Multiplexing: several transport layer connections on one network layer connection Flow control optional Expedited data optional

11. 18. Mar. 2004 11INF-3190: Transport Layer Transport Protocols Class TP 1: basic error recovery Class 0 including additional error recovery Error recovery masks resets TPDU numbering TPDU storage until ACK after reset: resynchronization Expedited data optional important data for example have a higher priority i.e. preferred processing before current data is processed Class TP 3: including multiplexing and error recovery Class 1 and 2 functions combined i.e. error recovery, expedited data, multiplexing

12. 18. Mar. 2004 12INF-3190: Transport Layer Transport Protocols Class TP 4: error monitoring and recovery Detects and recovers TPDU losses and TPDU duplication sequence errors Flow control Multiplexing Splitting (one transport connection uses several network connections) Expedited data Note IPv4 and IPv6 are connectionless Unavailable concepts in TCP/IP Multiplexing Splitting No clear definition for ST-II

13. 18. Mar. 2004 13INF-3190: Transport Layer Transport Protocols TCP/IP specifies protocols Services provided implicitely TCPUDPSCTPDCCP Connection-oriented service Connectionless service Ordered Reliable Unordered Unreliable With congestion control Without congestion control Multicast support Multihoming support XXX X XX XXX XX XXX XXX X XX X Partially OrderedX Partially Reliable X

14. 18. Mar. 2004 14INF-3190: Transport Layer Addressing at the Transport Layer Application Communication between applications required Application communicate locally by interprocess communication between system via transport services Transport layer Interprocess communication via communication networks Internet Protocol IP Enables endsystem-to-endsystem communication Telnet client Telnet server FTP client FTP server Web client Web server Transport Network Data link Physical

15. 18. Mar. 2004 15INF-3190: Transport Layer Addressing at the Transport Layer Transport address different from network address Sender (process) must address receiver (process) for connection setup or individual message Receiver (process) can be approached by the sender (process) Define transport addresses: ISO term: Transport Service Access Point (TSAP) Internet: port ATM: AAL-SAP 1-2 3 4 5 Transport Entity Network Layer Processes Transport Entity Network Layer Transport addresses Network addresses

16. 18. Mar. 2004 16INF-3190: Transport Layer Addressing at the Transport Layer 3 types of identifiers: names, addresses and routes [Shoch 78] “The name of a resource indicates WHAT we seek, an address indicates WHERE it is, and a route tells HOW TO GET THERE” Address identifies Type of service or application Addresses of services must be known Addressing by process number is unsuitable Processes are generated/terminated dynamically, i.e. the process number rarely known Relationship “service - process” not fix 1 process can supply multiple services Various processes can provide same service Port 1 Port 2 Port 3 Service A Service B Service C Port 4 Port 5

17. 18. Mar. 2004 17INF-3190: Transport Layer Addressing at the Transport Layer Communication ports Service Related to exactly one single port Port access Asynchronous or Synchronous Port Associated with buffer Buffer 1 Port 1 Service A Service BC Port 2 Port 3 Buffer 2 Buffer 3 Buffer 4 Buffer 5 Buffer

18. 18. Mar. 2004 18INF-3190: Transport Layer Addressing at the Transport Layer TCP and UDP have their own assignments this table shows some examples for TCP (read /etc/services for more) DecimalKeywordUNIX keywordDescription 0reserved 1TCPMUXTCP Multiplex 5RJERemote Job Entry 7ECHOechoEcho 9DISCARDdiscardDiscard 11USERSsystatActive Users 13DAYTIMEdaytimeDaytime 15 netstatNetwork Status Program 17QUOTEqotdQuote of the day 19CHARGENchargenCharacter Generator 20FTP-DATAftp-dataFile transfer protocol (data) 21FTPftpFile transfer protocol 23TELNETtelnetTerminal Connections 25SMTPsmtpSimple mail transfer protocol 37TIMEtimeTime 42NAMESERVERnameHost name server

19. 18. Mar. 2004 19INF-3190: Transport Layer Addressing at the Transport Layer DecimalKeywordUNIX keywordDescription 43NICNAMEwhoisWho is 53DOMAINnameserverDomain Name Server 77rjeAny private rje service 79FINGERfingerFinger 80HTTP World Wide Web 101HOSTNAMEhostnameNIC Host Name Server 102ISO-TSAPiso-tsapISO TSAP 103X400x400X.400 Mail Service 104X400-SNDx400-sndX.400 Mail Sending 110POP3pop3Remote Email Access 111SUN RPCsunrpcSUN Remote Procedure Call 113AUTHauthAuthentication Service 117UUCP-PATHuucp-pathUUCP path services 119NNTPnntpUSENET News Transfer Protocol 129PWDGENPassword Generator Protocol 139NETBIOS-SSNNETBIOS Session Protocol 160-1023Reserved

20. 18. Mar. 2004 20INF-3190: Transport Layer Addressing at the Transport Layer Application Example decompression of video data read process from database or file system Implementation of application process, thread Interface to communication systems buffers with predefined access mechanisms Sender and receiver create Stream or Socket several connections share a socket address: IP address of the endsystem address: 16-bit port number 0..1024: predefined ports, “well known” additional ones managed dynamically Example 192.169.100.17:80 socket with IP address 192.169.100.17 and port no. 80