Networking B.Ramamurthy Chapter 3 12/5/2018 B.Ramamurthy

Introduction Distributed systems use local area networks, wide area networks and internet for communication. Performance, reliability, scalability, mobility, and quality of service (qos) impact the design. Changes in user requirements have resulted in emergence of wireless and qos guarantees. Principles: protocol layering, packet switching, routing, data and behavior streaming. We will study: Ethernet, Asynchronous Transfer Mode (ATM), IEEE 802.11 wireless network standard. 12/5/2018 B.Ramamurthy

Networking Issues Performance: Scalability: Latency: delays at the switches and routers. Data transfer rate (bits/sec) : raw data Bandwidth: total volume of traffic that can be transferred across the network in a given time. Scalability: How does a system handle increase in the number of users? Increase in the size of the system? Increase in load and traffic? 12/5/2018 B.Ramamurthy

Networking Issues (contd.) Security: requirements and techniques for achieving security. Firewall, Virtual Private Network (VPN). Mobility: Support for moving devices. Not necessarily wireless. QoS: Bandwidth and latency bounds. 12/5/2018 B.Ramamurthy

Types of Networks Characterized by speed, communication medium, size, geographical distances, bandwidth, latency, technology. LAN : Single medium such as twisted pair of copper wires, coaxial cables, or optical fibers. Technology: Ethernet, token rings, slotted rings. WAN: Set of comm circuits (coax, satellite) linked by dedicated computers called routers. Technology: Switching. 12/5/2018 B.Ramamurthy

Types of Networks MAN: Wireless: High bandwidth copper or fiber optic cables. (phone lines, DSL, cable modem) Technology: Ethernet, IEEE802.6, ATM Wireless: Radio frequency, infrared, Technology: IEEE 802.11 (wavelan), CDPD, GSM, bluetooth (proximity) 12/5/2018 B.Ramamurthy

Figure 3.1 Network types Range Bandwidth (Mbps) Latency (ms) LAN 1-2 kms 10-1000 1-10 WAN worldwide 0.010-600 100-500 MAN 2-50 kms 1-150 10 Wireless LAN 0.15-1.5 km 2-11 5-20 Wireless WAN worldwide 0.010-2 100-500 Internet worldwide 0.010-2 100-500 12/5/2018 B.Ramamurthy

Internetworks Communication subsystem in which several networks are linked together to provide a data communication facilities that conceal the technologies and protocols of individual components. Gateways, switches, routers, compute and data servers. 12/5/2018 B.Ramamurthy

Networking Fundamentals Packet transmission Data Streaming Switching schemes Broadcast, circuit switching, packet switching, frame relay (ATM) Protocols Protocol layers Protocol suites Packet assembly Ports Addressing Packet delivery 12/5/2018 B.Ramamurthy

Networking Fundamentals (contd.) Routing Tables and algorithms Congestion control Internetworking IP address, protocol Routers Hubs Bridges Switches Tunnelling 12/5/2018 B.Ramamurthy

Conceptual layering of protocol software Message sent Message received Layer n Layer 2 Layer 1 Sender Communication Recipient medium 12/5/2018 B.Ramamurthy

Encapsulation as it is applied in layered protocols 12/5/2018 B.Ramamurthy

Protocols The term protocol refers to a well-known set of rules and formats to be used in order to perform a task. For example, a task of communicating between processes. Parts of a protocol: A specification of a sequence of messages that must be exchanged. A specification of the format of the data in the messages. Existence of well-known (standard) protocols enables the separate components of the distributed systems to be developed independently in different languages and on different platforms. 12/5/2018 B.Ramamurthy

ISO’s OSI Framework/Model ISO : International Standards Organization OSI : Open Systems Interconnection Services, interfaces, protocols Protocol Suite: Complete set of protocol layers is referred to as protocol stack or protocol suite. OSI Model defines the layers. For a protocol suite to be compliant with OSI it has defined a protocol for each of the layers specified in OSI model. 12/5/2018 B.Ramamurthy

OSI Protocol Layers Application: Communication requirements. Ex: HTTP, FTP, SMTP, CORBA IIOP Presentation: Bridges the data representation difference in the network and the computers; Encryption. Ex: Secure Sockets (SSL). Session: Reliability; Detection of failures and recovery. Ex: Checkpointing and recovery. Transport: Facilitates peer to peer process conversation. Port address concept. Ex: TCP (Transmission Control Protocol), UDP (User Datagram Protocol). Network: Transfers packets. Packet format that includes routing info. Ex: IP, ATM. Data Link: Responsible for data transfer between directly connected nodes (routers, hosts). Ex: PPP (Point-to-Point Protocol) Physical: The hardware circuits and binary transfer of data (optic, radio, microwave freq). Ex: ISDN (Integrated Service Digital Network), Cable modem. 12/5/2018 B.Ramamurthy

Ports and Addresses Ports are destination points within a host computer. Processes are attached to the ports, enabling them to communicate. Transport layer addresses are composed of network address of the host computer and a port number. In the Internet every host is assigned a unique IP number which is used in routing. In an Ethernet each host is responsible for recognizing that the messages meant for it. 12/5/2018 B.Ramamurthy

Routing in WAN Routers are computers with dedicated functionality. They determine the route of the packets using routing algorithms. A routing algorithm has two goals: It must make decisions that determine route taken by each packet as it travels through the network. It must dynamically update its knowledge of the network based on the traffic monitoring and detection of configuration changes or failures. Fine example of a distributed algorithm. We will examine a Router Information Protocol (RIP) 12/5/2018 B.Ramamurthy

Routing in a wide area network Hosts Links or local networks A D E B C 1 2 5 4 3 6 Routers 12/5/2018 B.Ramamurthy

Routing tables for the network in Last Slide Routings from A Routings from B Routings from C To Link Cost A B C D E local 1 3 2 4 5 Routings from D Routings from E To Link Cost A B C D E 3 6 local 1 2 4 5 12/5/2018 B.Ramamurthy

Pseudo-code for RIP routing algorithm Send: Each t seconds or when Tl changes, send Tl on each non-faulty outgoing link. Receive: Whenever a routing table Tr is received on link n: for all rows Rr in Tr { if (Rr.link < > n) { Rr.cost = Rr.cost + 1; Rr.link = n; if (Rr.destination is not in Tl) add Rr to Tl; // add new destination to Tl else for all rows Rl in Tl { if (Rr.destination = Rl.destination and (Rr.cost < Rl.cost or Rl.link = n)) Rl = Rr; // Rr.cost < Rl.cost : remote node has better route // Rl.link = n : remote node is more authoritative } 12/5/2018 B.Ramamurthy

Internetworking Local networks are built using Ethernet and ATM. Wide area networks are built using telephone lines, satellite links, wide-area ATM, ISDN, etc. Internetworking is connecting all these subnets of differing technologies. Issues? 12/5/2018 B.Ramamurthy

Problems in Internetworking A unified internetwork addressing scheme that enables packets to be addressed to any host connected to any subnet. A protocol defining the format of internetwork packets and giving rules according to which they are to be handled. Interconnecting components that route packets to their destinations. 12/5/2018 B.Ramamurthy

Solutions provided by the Internet For the Internet, Problem 1) is solved by IP addresses Problem 2) is addresses by IP protocol Problem 3) is performed by components called Internet Routers. 12/5/2018 B.Ramamurthy

Simplified view of the QMW Computer Science network file compute dialup hammer henry hotpoint 138.37.88.230 138.37.88.162 bruno 138.37.88.249 router/ sickle 138.37.95.241 138.37.95.240/29 138.37.95.249 copper 138.37.88.248 firewall web 138.37.95.248/29 server desktop computers 138.37.88.xx subnet Eswitch 138.37.88 138.37.88.251 custard 138.37.94.246 138.37.94 hub Student subnet Staff subnet other servers 138.37.94.251 % 1000 Mbps Ethernet Eswitch: Ethernet switch 100 Mbps Ethernet file server/ gateway printers Campus router 138.37.94.xx 12/5/2018 B.Ramamurthy

TCP/IP layers Message Layers Application Messages (UDP) or Streams (TCP) Application Transport Internet UDP or TCP packets IP datagrams Network-specific frames Message Layers Underlying network Network interface 12/5/2018 B.Ramamurthy

Encapsulation in a message transmitted via TCP over an Ethernet Application message TCP header IP header Ethernet header Ethernet frame port TCP IP 12/5/2018 B.Ramamurthy

The programmer's conceptual view of a TCP/IP Internet 12/5/2018 B.Ramamurthy

Internet address structure, showing field sizes in bits 12/5/2018 B.Ramamurthy

Decimal representation of Internet addresses 12/5/2018 B.Ramamurthy

IP packet layout 12/5/2018 B.Ramamurthy

Issues in IPV4 Address limitations Scarcity of Class B addresses Managing entries in routing tables Ad hoc measures such as allocation Class C to Class B address ranges (CIDR – classless interdomain routing). 12/5/2018 B.Ramamurthy

IPV6 Features Addresses are 128 bits (double that of IPV4) Address space is partitioned Routing speed improved by removing some operations such as checksum. Accommodates real-time and special services. (streams and devices) Future evolution possible (next header field). IPV6 support “anycast” (message delivered to at least one of the hosts). Built-in security. 12/5/2018 B.Ramamurthy

IPv6 header layout 12/5/2018 B.Ramamurthy

Tunnelling for IPv6 migration B IPv6 IPv6 encapsulated in IPv4 packets Encapsulators IPv4 network 12/5/2018 B.Ramamurthy

Mobile IP Laptops and handheld devices that may be connected to the network at different locations. It needs a new IP address at every site. But many applications require that mobile client retain a single IP address. When the device is mobile, home agent and foreign agent work on behalf of the client. 12/5/2018 B.Ramamurthy

The MobileIP routing mechanism Sender Subsequent IP packets tunnelled to FA Mobile host MH Address of FA returned to sender First IP packet addressed to MH Internet Foreign agent FA Home First IP packet agent tunnelled to FA 12/5/2018 B.Ramamurthy