CMPT 771/471: Internet Architecture & Protocols School of Computing Science Simon Fraser University CMPT 771/471: Internet Architecture & Protocols Introduction Instructor: Dr. Mohamed Hefeeda

Course Objectives Understand Know how to And, more importantly, … principles of designing and operating computer networks structure and protocols of the Internet services that can/cannot be offered by the Internet Know how to analytically analyze performance of a system/protocol implement network protocols and applications And, more importantly, … Have fun!

Course Info Most of the course will be lectures given by the instructor Last 2 weeks, each graduate student gives a presentation on one of a preselected networking topics Course web page http://nsl.cs.sfu.ca/teaching/09/771/ Or access it from my web page: http://www.cs.sfu.ca/~mhefeeda

Course Info: Textbooks and References Kurose and Rose, Computer Networking:  A top-down Approach Featuring the Internet, lastest ed. Required Background materials Chapters 6 and 7: Wireless and Multimedia Networking Hassan and Jain, High Performance TCP/IP Networking, 2004  Several chapters on analyzing TCP/IP in different environments Stallings, High-speed Networks and Internets: Performance and Quality of Service, 2002 Three chapters on (basics of) probability and queuing Papers: will be posted on the course web page

Course Info: Grading Homework and presentations: 20% Projects: 40% 3 – 4 problem sets Projects: 40% Several projects; some in group of two students All in C Must read Assignment Policy Exam: 40% Comprehensive In the last week of classes (during class time)

Course Info: Topics Internet Architecture and Services TCP/IP Protocol Suit Inter- and Intra-domain Routing Protocols Introduction to Performance Modeling and Evaluation TCP/IP Performance Modeling in Different Environments Quality of Service Support in the Internet Wireless Networks Multimedia Networking Overlays and Peer-to-Peer Computing

Basic Networking Concepts

Review of Basic Networking Concepts Internet structure Protocol layering and encapsulation Internet services and socket programming Network Layer Network types: Circuit switching, Packet switching Addressing, Forwarding, Routing Transport layer Reliability and congestion control TCP, UDP Link Layer Multiple Access Protocols Ethernet

The Internet Millions of hosts (end systems) router workstation Inter-connected, running network apps Diverse communication links fiber, copper, radio, satellite Routers forward packets Internet: “network of networks” loosely hierarchical Public, versus private intranet local ISP company network regional ISP router workstation server mobile

Internet structure: network of networks roughly hierarchical at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage treat each other as equals NAP Tier-1 providers also interconnect at public network access points (NAPs) Tier 1 ISP Tier-1 providers interconnect (peer) privately Tier 1 ISP Tier 1 ISP

Tier-1 ISP: e.g., Sprint Sprint US backbone network … …. DS3 (45 Mbps) OC3 (155 Mbps) OC12 (622 Mbps) OC48 (2.4 Gbps) Seattle Atlanta Chicago Roachdale Stockton San Jose Anaheim Fort Worth Orlando Kansas City Cheyenne New York Pennsauken Relay Wash. DC Tacoma … to/from customers peering to/from backbone …. POP: point-of-presence

Internet structure: Tier-2 ISPs “Tier-2” ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier-2 ISPs also peer privately with each other, interconnect at NAP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet Tier-2 ISP is customer of tier-1 provider Tier 1 ISP NAP Tier 1 ISP Tier 1 ISP

Internet structure: Tier-3 ISPs “Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems) local ISP Tier 3 Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet Tier-2 ISP Tier 1 ISP NAP Tier 1 ISP Tier 1 ISP

Internet structure: packet journey a packet passes through many networks! local ISP Tier 3 ISP local ISP local ISP local ISP Tier-2 ISP Tier 1 ISP NAP Tier 1 ISP Tier 1 ISP local ISP local ISP local ISP local ISP

Review of Basic Networking Concepts Internet structure Protocol layering and encapsulation Internet services and socket programming Network Layer Network types: Circuit switching, Packet switching Addressing, Forwarding, Routing Transport layer Reliability and congestion control TCP, UDP Link Layer Multiple Access Protocols Ethernet

Protocol Layers Question: Networks are complex! many “pieces”: hosts routers links of various media applications protocols hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks?

Layering of Airline Functionality ticket (purchase) baggage (check) gates (load) runway (takeoff) airplane routing departure airport arrival intermediate air-traffic control centers ticket (complain) baggage (claim gates (unload) runway (land) ticket baggage gate takeoff/landing Layers: each layer implements a service via its own internal-layer actions relying on services provided by layer below

Why layering? Dealing with complex systems: explicit structure allows identifying complex relationships among system’s pieces modularization eases maintenance, updating of system change of implementation of layer’s service transparent to rest of system e.g., change in gate procedure doesn’t affect rest of system What is the downside of layering?

Internet protocol stack application: supporting network applications FTP, SMTP, HTTP transport: process-process data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements PPP, Ethernet physical: bits “on the wire” application transport network link physical

Encapsulation source destination application transport network link router switch message M application transport network link physical segment Ht M datagram Ht Hn M frame Ht Hn Hl M Ht Hn Hl M Ht Hn Hl M Ht Hn M Ht Hn M Ht Hn Hl M M Ht Hn Hl M Ht M Ht Hn M Ht Hn Hl M

Review of Basic Networking Concepts Internet structure Protocol layering and encapsulation Internet services and socket programming Network Layer Network types: Circuit switching, Packet switching Addressing, Forwarding, Routing Transport layer Reliability and congestion control TCP, UDP Link Layer Multiple Access Protocols Ethernet

Internet Services View the Internet as a communication infrastructure that provides services to apps Web, email, games, e-commerce, file sharing, … Two communication services Connectionless unreliable Connection-oriented reliable

How can we access these services? Internet Services Connection-oriented Prepare for data transfer ahead of time establish connection  set up state in the two communicating hosts Usually comes with reliability, flow and congestion control TCP: Transmission Control Protocol Connectionless No connection set up, simply send Faster, less overhead No reliability, flow control, or congestion control UDP: User Datagram Protocol How can we access these services?

Network (Socket) Programming Process sends/receives messages to/from its socket Socket analogous to door sending process shoves message out door sending process relies on transport infrastructure on other side of door which brings message to socket at receiving process process TCP with buffers, variables socket host or server process TCP with buffers, variables socket host or server controlled by app developer Internet controlled by OS Socket is the interface (API) between application and transport layer

Addressing Processes For a process to receive messages, it must have an identifier A host has a unique32-bit IP address Q: does the IP address of the host on which the process runs suffice for identifying the process? A: No, many processes can be running on same host  We use ports Process is identified by: IP address, Transport protocol, and Port number Example port numbers: HTTP server: 80 (TCP) Mail server: 25 (TCP)

Socket Programming Socket API introduced in BSD 4.1 UNIX, 1981 explicitly created, used, released by apps client/server paradigm provides two services reliable, byte stream-oriented unreliable datagram

Socket Programming using TCP TCP service: reliable transfer of bytes from one process to another virtual pipe between sender and receiver controlled by application developer controlled by application developer process TCP with buffers, variables socket process TCP with buffers, variables socket controlled by operating system controlled by operating system internet host or server host or server

Socket Programming using TCP Server (running on hostid) Client create socket, port=x, for incoming request: welcomeSocket = ServerSocket() TCP connection setup create socket, connect to hostid, port=x clientSocket = Socket() wait for incoming connection request connectionSocket = welcomeSocket.accept() send request using clientSocket read request from connectionSocket write reply to read reply from clientSocket close connectionSocket close clientSocket

Socket Programming using TCP Server process must first be running, and creates a socket (door) that welcomes client’s contact, then wait Client contacts server by creating local TCP socket using IP address, port number of server process When client creates socket client TCP establishes connection to server TCP When contacted by client server TCP creates new socket for server process to communicate with client allows server to talk with multiple clients source port numbers and IPs used to distinguish clients A stream is a sequence of characters that flow into or out of a process.

Socket programming using UDP UDP Service: unreliable transfer of groups of bytes (datagrams) between client and server no connection between client and server no handshaking sender explicitly attaches IP address and port of destination to each packet server must extract IP address, port of sender from received packet transmitted data may be received out of order, or lost

Socket Programming using UDP Server (running on hostid) Client create socket, port=x, for incoming request: serverSocket = DatagramSocket() read request from serverSocket create socket, clientSocket = DatagramSocket() read reply from clientSocket Create datagram (hostid,port=x,data) send datagram request using clientSocket write reply to serverSocket specifying client host address, port number close clientSocket