Shambhu J Upadhyaya 1 Shambhu Upadhyaya Computer Science & Eng. University at Buffalo Buffalo, New York COMMUNICATION PROTOCOLS

Part I  LAN, WAN, MAN  TCP/IP Protocol architecture, OSI Model  Spread spectrum concept – FHSS, DSSS  Coding and error control  Generations of cellular networks (1G, 2G, 3G, 4G)  Cordless systems  WiMax & IEEE Broadband wireless access standards  Mobile IP Shambhu Upadhyaya 2

Reading Exercise  IPV4  IPV6  (To be revisited at the end of lecture) Shambhu Upadhyaya 3

Key Features of a Protocol  Enables high degree of cooperation between two computer systems by working in smaller subtasks (bricks analogy)  A protocol is characterized by:  Syntax  Concerns the format of the data blocks  Semantics  Includes control information for coordination and error handling  Timing  Includes speed matching and sequencing Shambhu Upadhyaya 4

Agents Involved in Communication  Applications  Exchange data between computers (e.g., electronic mail, file transfer)  Computers  Connected to networks  Networks  Transfers data from one computer to another Shambhu Upadhyaya 5

TCP/IP Layers  Application layer  Host-to-host, or transport layer  Internet layer  Network access layer  Physical layer Shambhu Upadhyaya 6

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 Shambhu Upadhyaya 7

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 (X.25, ATM, Frame Relay)  LANs (e.g., Ethernet)  Others Shambhu Upadhyaya 8

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 Shambhu Upadhyaya 9

TCP/IP Host-to-Host, or Transport Layer  Commonly uses transmission control protocol (TCP)  Provides reliability during data exchange  Completeness  Order Shambhu Upadhyaya 10

TCP/IP Application Layer  Logic supports user applications  Uses separate modules that are peculiar to each different type of application Shambhu Upadhyaya 11

Steps in Sending a Message Shambhu Upadhyaya 12

Protocol Data Units (PDUs) Shambhu Upadhyaya 13

Common TCP/IP Applications  Simple mail transfer protocol (SMTP)  Provides a basic electronic mail facility  Features – mailing lists, return receipts  File Transfer Protocol (FTP)  Allows files to be sent from one system to another – text, binary files  TELNET  Provides a remote logon capability Shambhu Upadhyaya 14

Layers of the OSI Model  Application  Presentation  Session  Transport  Network  Data link  Physical Shambhu Upadhyaya 15

OSI Application Layer  Provides access to the OSI environment for users  Provides distributed information services Shambhu Upadhyaya 16

OSI Presentation Layer  Provides independence to the application processes from differences in data representation (syntax) Shambhu Upadhyaya 17

OSI Session Layer  Provides the control structure for communication between applications  Establishes, manages, and terminates connections (sessions) between cooperating applications Shambhu Upadhyaya 18

OSI Transport Layer  Provides reliable, transparent transfer of data between end points  Provides end-to-end error recovery and flow control Shambhu Upadhyaya 19

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 Shambhu Upadhyaya 20

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 Shambhu Upadhyaya 21

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 Shambhu Upadhyaya 22

Comparison of OSI and TCP/IP Shambhu Upadhyaya 23

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 Shambhu Upadhyaya 24

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  Interactions between layers and mechanism  Entities are referenced by means of a service access point (SAP)  The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer  E.g., NSAP (network layer) is similar to IP address Shambhu Upadhyaya 25

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 Shambhu Upadhyaya 26

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  E.g., Cisco Aironet 1400 Wireless Bridge  Connects multiple LANs in a metro area  Router – an IS used to connect two networks that may or may not be similar Shambhu Upadhyaya 27

Functions of a Router  Provide a link between networks  E.g., Cisco Linksys - Dual-Band Wireless-N Router with 4-Port Ethernet Switch  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 Shambhu Upadhyaya 28

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 Shambhu Upadhyaya 29

Internetworking Illustration Shambhu Upadhyaya 30

Operation of Routers  IP is implemented in all end systems and routers  End systems must have compatible protocols above IP  Routers need only have up through IP Shambhu Upadhyaya 31

Operation, Contd.  Block of data from X to Y  PDU is created and IP layer attaches a header (global Internet address of Y)  Since Y is on another network, the packet needs to be sent to router 1 in the form of an LLC PDU  Upon receiving, MAC layer constructs a MAC packet and sticks in the address of router 1  After examination, router 1 routes packets to router 2 (wrapping in another format if necessary)  Router 2 strips off header to determine that the IP packet is destined to Y  Router 2 creates a packet with destination address of Y and sends it onto the LAN  Y removes all headers and forwards data to upper layer Shambhu Upadhyaya 32

Router, Switch and Hub  Router is like a computer- acts as gateway  Joins together multiple LANs to a WAN  Works at layer 3 of OSI  Switch is less sophisticated  Must designate a computer as a gateway  Works at layer 2 of OSI  Connects devices to form a LAN  Hub is used to connect segments of LAN  Works at layer 1 of OSI  It is like a splitter Shambhu Upadhyaya 33

IPv4  20 bytes or 160 bits (minimum)  32 bit address (4.3 billion IP addresses)  Study shows that available address space would not last long  In April 2014, North American Registry for Internet Numbers (ARIN), announced it had reached "phase 4" of its IPv4 countdown plan, with fewer than 17 million IPv4 addresses remaining Shambhu Upadhyaya 34

IPv6  Fixed length of 40 octets  128 bit addresses (5x10 28 addresses for each of 7B people)  U.S. government specified network backbones at federal agencies must deploy IPv6 by 2008 – the adoption is slow due to lack of client base  Major backbone networks – Amazon, Comcast, HSBC, Akamai, Verizon, etc. have deployed IPv6 Shambhu Upadhyaya 35

IPv4, IPv6 Summary  IPv4 will soon run out of address space  IPv6 initiative started in 1995 but adoption is slow, will become main stream soon  Products such as Microsoft OS have support for IPv6 and are enabled by default  IPv6 has no backward compatibility since headers are significantly different  You need to run dual stacks to serve both types of networks  Situation is similar to WEP and RSN in the wireless security domain Shambhu Upadhyaya 36

References  Corey Beard & William Stallings, Wireless Communication Networks and Systems, Pearson, 2016 (Chapter 4)  Wikipedia Shambhu Upadhyaya 37