ECEN 619 “Internet Protocols and Modeling” Course Materials: Papers, Reference Texts: Bertsekas/Gallager, Stuber, Stallings, etc Grading (Tentative): HW: 20%, Projects: 40%, Exam-1:20%, Exam-II:20% Lecture notes and Paper Reading Lists: available on-line: TBA Class Website: Research Interests and Projects: URL: Instructor: Professor Xi Zhang Office: WERC 331D

Protocols and the TCP/IP Suite Introductions and Overviews

Key Features of a Protocol Syntax –Concerns the format of the data blocks Semantics –Includes control information for coordination and error handling Timing –Includes speed matching and sequencing

Agents Involved in Communication Applications –Exchange data between computers (e.g., electronic mail) Computers –Connected to networks Networks –Transfers data from one computer to another

TCP/IP Layers Physical layer Network access layer Internet layer Host-to-host, or transport layer Application layer

TCP/IP Physical Layer Covers the physical interface between a data transmission device and a transmission medium or network Physical layer specifies: –Characteristics of the transmission medium –The nature of the signals –The data rate –Other related matters

TCP/IP Network Access Layer Concerned with the exchange of data between an end system and the network to which it's attached Software used depends on type of network –Circuit switching –Packet switching (e.g., X.25) –LANs (e.g., Ethernet) –Others

TCP/IP Internet Layer Uses internet protocol (IP) Provides routing functions to allow data to traverse multiple interconnected networks Implemented in end systems and routers

TCP/IP Host-to-Host, or Transport Layer Commonly uses transmission control protocol (tcp) Provides reliability during data exchange –Completeness –Order

TCP/IP Application Layer Logic supports user applications Uses separate modules that are peculiar to each different type of application

Protocol Data Units (PDUs)

Common TCP/IP Applications Simple mail transfer protocol (SMTP) –Provides a basic electronic mail facility File Transfer Protocol (FTP) –Allows files to be sent from one system to another TELNET –Provides a remote logon capability

Layers of the OSI Model Application Presentation Session Transport Network Data link Physical

OSI Application Layer Provides access to the OSI environment for users Provides distributed information services

OSI Presentation Layer Provides independence to the application processes from differences in data representation (syntax)

OSI Session Layer Provides the control structure for communication between applications Establishes, manages, and terminates connections (sessions) between cooperating applications

OSI Transport Layer Provides reliable, transparent transfer of data between end points Provides end-to-end error recovery and flow control

OSI Network Layer Provides upper layers with independence from the data transmission and switching technologies used to connect systems Responsible for establishing, maintaining, and terminating connections

OSI Data link Layer Provides for the reliable transfer of information across the physical link Sends blocks (frames) with the necessary synchronization, error control, and flow control

OSI Physical Layer Concerned with transmission of unstructured bit stream over physical medium Deals with accessing the physical medium –Mechanical characteristics –Electrical characteristics –Functional characteristics –Procedural characteristics

Comparison of OSI and TCP/IP

TCP/IP Architecture Dominance TCP/IP protocols matured quicker than similar OSI protocols –When the need for interoperability across networks was recognized, only TCP/IP was available and ready to go OSI model is unnecessarily complex –Accomplishes in seven layers what TCP/IP does with fewer layers

Elements of Standardization within OSI Framework Protocol Specification –Format of protocol data units (PDUs) exchanged –Semantics of all fields –Allowable sequence of PDUs Service Definition –Functional description that defines what services are provided, but not how the services are to be provided Addressing –Entities are referenced by means of a service access point (SAP)

Internetworking Terms Communication network – facility that provides a data transfer service among devices attached to the network Internet – collection of communication networks, interconnected by bridges/routers Intranet – internet used by an organization for internal purposes –Provides key Internet applications –Can exist as an isolated, self-contained internet

Internetworking Terms End System (ES) – device used to support end-user applications or services Intermediate System (IS) – device used to connect two networks Bridge – an IS used to connect two LANs that use similar LAN protocols Router - an IS used to connect two networks that may or may not be similar

Functions of a Router Provide a link between networks Provide for the routing and delivery of data between processes on end systems attached to different networks Provide these functions in such a way as not to require modifications of the networking architecture of any of the attached subnetworks

Network Differences Routers Must Accommodate Addressing schemes –Different schemes for assigning addresses Maximum packet sizes –Different maximum packet sizes requires segmentation Interfaces –Differing hardware and software interfaces Reliability –Network may provide unreliable service

28 Packet Switched Networks Hosts send data in packets network supports all data communication services by delivering packets –Web, , multimedia Host Application Host Web Host video

29 One network application example msg

30 What is happening inside ? msg Physical net physical net Physical net Network protocol Network protocol Network protocol Network protocol Transport protocol Transport protocol

31 A B C network topology Layered Network Architecture network consists of geographically distributed hosts and switches (nodes) Nodes communicate with each other by standard protocols B A C physical connectivity Protocol layers D host switch

32 Ethernet frame network packet Transport segment header tail header DATA data What’s in the header: info needed for the protocol’s function Application (data) B A physical connectivity a picture of protocol layers

33 TCP/IP Protocol Suite IP Protocol: Inter-networking protocol –RFC791 TCP Protocol: reliable transport protocol –RFC793

34 transport (end-to-end) subnets ethernet token-ring FDDI dialup ATM IP TCP UDP inter-network layer application protocols transport layer protocols universal datagram delivery hardware-specific network technologies The picture of the world according to IP

35 TCP: Transmission Control Protocol a transport protocol –IP delivers packets “from door to door” –TCP provides full-duplex, reliable byte-stream delivery between two application processes Application process Write bytes TCP Send buffer Application process Read bytes TCP Receive buffer segment More terminology: TCP segment Max. segment size ( MSS )

36 TCP: major functionalities Header format Connection Management Open, close State management Reliability management Flow and Congestion control Flow control: Do not flood the receiver’s buffer Congestion control: Do not stress the network by sending too much too fast

37 u a p r s f r c s s y i g k h t n n source portdestination port Data sequence number acknowledgment number Hlen unused window size checksumurgent pointer Options (viable length) TCP header format data IP header

38 client server open request(x) Passive open ack(x+1) + request(y) ack(y+1) (now in estab. state) enter estab. state opening a connection: three-way hand-shake

39 TCP’s Two Major Functional Components [1] Flow control and congestion control –Refer to a set of techniques enabling a data source to match its transmission rate to the currently available service rate at the receiver and in the networks. –Flow Control Mechanism Design Ceriteria »Simple to implement and use least network resources »Scales well as the network size increases »Must be stable and converging to equilibriums [2] Error Control and Loss Recovery –Refer to a set of techniques to detect and correct data losses –Two levels of error control »Bit-level: inversion of 0 bit to 1, or 1 bit to 0, also called bit corruption => often occur over the mobile and wireless networks »Packet-level: packet loss, duplications, reordering => often occur and be treated at higher layer protocol, such as TCP, over wired networks. »Erasure error: the information about the positions of error/loss is available for error control => packet level loss usually be treated as erasure loss by using sequence number.

40 Classification of Flow Control Mechanisms Open-loop control scheme –Flow control function is achieved without using feedback via the closed-loop channel. Closed-loop flow control scheme –Flow control adapt its transmission rate to the bottleneck available bandwidth according to the feedback through the closed-loop channel »Window-based scheme vs. Rate-based schemes »Explicit scheme vs. Implicit scheme »End-to-end scheme vs. Hop-by-Hop scheme Hybrid schemes –Mixing open-loop flow control with closed-loop scheme

41 TCP Flow Control Categories and Principles Flow control categories –Implicit, –Window-based, –End-to-End scheme. TCP Hahoe –Use timeout to detect packet loss and congestions TCP Reno –Use triple-duplicate ACK to same sequence number and timeouts to detect packet loss and congestions –Use fast retransmissions and fast recovery »Skip Slow Start phase TCP Vegas –Use expected and measured throughputs to detect congestions

References Basic knowledge of calculus Programming experiences –familiar with C/C++/UNIX –useful reference books: “Internetworking with TCP/IP, Vol’s I, II, III” by Doug Comer “TCP/IP Illustrated, Vol’s 1 & 2” by Stevens

References Probability Theories & Applications –Discrete vs. continuing random variables –Probability distribution functions –Stochastic process Optimization Principles