Networking B Ramamurthy Chapter 3 152022 B Ramamurthy

Networking B. Ramamurthy Chapter 3 1/5/2022 B. Ramamurthy 1

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. 1/5/2022 B. Ramamurthy 2

Networking Issues Performance: n n n 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: n 1/5/2022 How does a system handle increase in the number of users? Increase in the size of the system? Increase in load and traffic? B. Ramamurthy 3

Networking Issues (contd. ) Security: requirements and techniques for achieving security. Firewall, Virtual Private Network (VPN). Mobility: Support for moving devices. Not necessarily wireless. Qo. S: Bandwidth and latency bounds. 1/5/2022 B. Ramamurthy 4

Types of Networks Characterized by speed, communication medium, size, geographical distances, bandwidth, latency, technology. LAN : n n Single medium such as twisted pair of copper wires, coaxial cables, or optical fibers. Technology: Ethernet, token rings, slotted rings. WAN: n n 1/5/2022 Set of comm circuits (coax, satellite) linked by dedicated computers called routers. Technology: Switching. B. Ramamurthy 5

Types of Networks MAN: n n High bandwidth copper or fiber optic cables. (phone lines, DSL, cable modem) Technology: Ethernet, IEEE 802. 6, ATM Wireless: n n 1/5/2022 Radio frequency, infrared, Technology: IEEE 802. 11 (wavelan), CDPD, GSM, bluetooth (proximity) B. Ramamurthy 6

Figure 3. 1 Network types Range LAN 1 -2 kms WAN worldwide MAN 2 -50 kms Wireless LAN 0. 15 -1. 5 km Wireless WAN worldwide Internet worldwide 1/5/2022 Bandwidth (Mbps) Latency (ms) 10 -1000 0. 010 -600 1 -150 2 -11 0. 010 -2 B. Ramamurthy 1 -10 100 -500 10 5 -20 100 -500 7

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. 1/5/2022 B. Ramamurthy 8

Networking Fundamentals Packet transmission Data Streaming Switching schemes n Broadcast, circuit switching, packet switching, frame relay (ATM) Protocols n n n 1/5/2022 Protocol layers Protocol suites Packet assembly Ports Addressing Packet delivery B. Ramamurthy 9

Networking Fundamentals (contd. ) Routing n Tables and algorithms Congestion control Internetworking n n n 1/5/2022 IP address, protocol Routers Hubs Bridges Switches Tunnelling B. Ramamurthy 10

Conceptual layering of protocol software Message received Message sent Layer n Layer 2 Layer 1 Sender 1/5/2022 Communication medium B. Ramamurthy Recipient 11

Encapsulation as it is applied in layered protocols 1/5/2022 B. Ramamurthy 12

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: n A specification of a sequence of messages that must be exchanged. n 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. 1/5/2022 B. Ramamurthy 13

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. 1/5/2022 B. Ramamurthy 14

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. 1/5/2022 B. Ramamurthy 15

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. 1/5/2022 B. Ramamurthy 16

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: n It must make decisions that determine route taken by each packet as it travels through the network. n It must dynamically update its knowledge of the network based on the traffic monitoring and detection of configuration changes or failures. n Fine example of a distributed algorithm. We will examine a Router Information Protocol (RIP) 1/5/2022 B. Ramamurthy 17

Routing in a wide area network A Hosts or local networks 1 3 B 2 Links 4 C 5 D 6 E Routers 1/5/2022 B. Ramamurthy 18

Routing tables for the network in Last Slide Routings from A To Link Cost A local 0 B 1 1 C 1 2 D 3 1 E 1 2 Routings from B To Link Cost A 1 1 B local 0 C 2 1 D 1 2 E 4 1 Routings from D To Link Cost A 3 1 B 3 2 C 6 2 D local 0 E 6 1 1/5/2022 B. Ramamurthy Routings from C To Link Cost A 2 2 B 2 1 C local 0 D 5 2 E 5 1 Routings from E To Link Cost A 4 2 B 4 1 C 5 1 D 6 1 E local 0 19

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 } } } 1/5/2022 B. Ramamurthy 20

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? 1/5/2022 B. Ramamurthy 21

Problems in Internetworking 1. A unified internetwork addressing scheme that enables packets to be addressed to any host connected to any subnet. 2. A protocol defining the format of internetwork packets and giving rules according to which they are to be handled. 3. Interconnecting components that route packets to their destinations. 1/5/2022 B. Ramamurthy 22

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. 1/5/2022 B. Ramamurthy 23

Simplified view of the QMW Computer Science network Campus 138. 37. 95. 240/29 router subnet 138. 37. 95. 241 hammer Staff subnet 138. 37. 88 compute server router/ firewall 138. 37. 88. 251 Student subnet 138. 37. 94. 251 Eswitch bruno 138. 37. 88. 249 % 138. 37. 94 file server/ gateway custard 138. 37. 94. 246 dialup server henry 138. 37. 88. 230 printers other servers file server hotpoint 138. 37. 88. 162 web server copper 138. 37. 88. 248 hub desktop computers 138. 37. 88. xx Campus 138. 37. 95. 248/29 subnet router 1/5/2022 desktop computers 138. 37. 94. xx sickle router/ 138. 37. 95. 249 firewall B. Ramamurthy 100 Mbps Ethernet 1000 Mbps Ethernet Eswitch: Ethernet switch 24

TCP/IP layers Layers Message Application Messages (UDP) or Streams (TCP) Transport UDP or TCP packets Internet IP datagrams Network interface Network-specific frames Underlying network 1/5/2022 B. Ramamurthy 25

Encapsulation in a message transmitted via TCP over an Ethernet Application message TCP header port IP header TCP Ethernet header IP Ethernet frame 1/5/2022 B. Ramamurthy 26

The programmer's conceptual view of a TCP/IP Internet 1/5/2022 B. Ramamurthy 27

Internet address structure, showing field sizes in bits 1/5/2022 B. Ramamurthy 28

Decimal representation of Internet addresses 1/5/2022 B. Ramamurthy 29

IP packet layout 1/5/2022 B. Ramamurthy 30

Issues in IPV 4 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). 1/5/2022 B. Ramamurthy 31

IPV 6 Features Addresses are 128 bits (double that of IPV 4) 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). IPV 6 support “anycast” (message delivered to at least one of the hosts). Built-in security. 1/5/2022 B. Ramamurthy 32

IPv 6 header layout 1/5/2022 B. Ramamurthy 33

Tunnelling for IPv 6 migration IPv 6 encapsulated in IPv 4 packets A IPv 6 IPv 4 network IPv 6 B Encapsulators 1/5/2022 B. Ramamurthy 34

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. 1/5/2022 B. Ramamurthy 35

The Mobile. IP routing mechanism Sender Address of FA returned to sender Subsequent IP packets tunnelled to FA Mobile host MH First IP packet addressed to MH Internet Home agent 1/5/2022 Foreign agent FA First IP packet tunnelled to FA B. Ramamurthy 36