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Berkeley ELENG 122 - Midterm Review EE 122

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Two fundamentally different ways to forward information Midterm Review Circuit Switched EECS 122 Lecture 1 Information is exchanged in units of calls Network resources are reserved for the duration of the call Example The Phone Network Packet Switched Department of Electrical Engineering and Computer Sciences University of California Berkeley Information is exchanged in units of packets Typically no resources are reserved Datagram Each packet is forward independently March 9 2006 Big Picture Applications Transport Network Layer Routing Protocols QoS 4 Backbone Network Class Based Classless Addressing Dijkstra Bellman Ford BGP EECS122 Lecture Midterm Review DNS HTTP SMTP Network Layer Forwarding Example ATM ISDN Intserv Layers Where protocols are implemented Switching Techniques Example The Internet Virtual Circuit All the packets from a given stream take the same path through the network Review Check List Once a call goes through subsequent calls cannot degrade call quality Architecture Input Output Fabric Architectures Shared Bus Shared Mem Switched Basic Performance Metrics Packet Delay Little s Law Max Min Fairness Mechanisms for QoS Scheduling Fairness GPS WFQ Intserv Diffserv Internet Multimedia Streaming and VOIP March 9 2006 2 EECS122 Lecture Midterm Review The internet consists of many networks local ISP Many Internet Service Providers at each level of the Hierarchy Tier 3 ISP local ISP Tier 2 ISP Tier 2 ISP local local ISP ISP March 9 2006 EECS122 Lecture Midterm Review 5 Metropolitan Area Network local ISP local ISP Tier 2 ISP Tier 1 ISP Tier 1 ISP March 9 2006 NAP Tier 1 ISP Tier 2 ISP local ISP EECS122 Lecture Midterm Review Tier 2 ISP local ISP 3 March 9 2006 EECS122 Lecture Midterm Review 6 1 Campus Network The Network Core Many interconnected subnetworks Many different architectures Advertises a service to the end devices March 9 2006 EECS122 Lecture Midterm Review 7 Local Area Network March 9 2006 application supporting network applications network routing of datagrams from source to destination link data transfer between neighboring network elements run application programs e g Web email at edge of network client server model IP routing protocols link physical PPP Ethernet physical bits on the wire March 9 2006 11 EECS122 Lecture Midterm Review end systems hosts network Layering of airline functionality The network edge transport TCP UDP 8 application FTP SMTP HTTP transport host host data transfer EECS122 Lecture Midterm Review 10 EECS122 Lecture Midterm Review Internet protocol stack March 9 2006 E g Phone network v s the Internet client host requests receives service from always on server e g Web browser server email client server EECS122 Lecture Midterm Review ticket baggage claim baggage gates load gates unload gate runway takeoff runway land takeoff landing airplane routing airplane routing departure airport airplane routing airplane routing intermediate air traffic control centers arrival airport Layers each layer implements a service via its own internal layer actions relying on services provided by layer below minimal or no use of dedicated servers e g Gnutella KaZaA Skype March 9 2006 ticket complain airplane routing peer peer model ticket purchase baggage check 9 March 9 2006 EECS122 Lecture Midterm Review 12 2 An Advanced View of Internet Layering Application TCP BGP UDP IP HTTP Almost Any kind of application can write directly on IP Network RTP TCP TFTP UDP DNS Features root Including new transport protocols IP cannot be avoided As long as the routers speak IP any application that can make do with datagram service can be written and implemented on the end devices No co ordination standards activity etc is required edu gov com eecs mit berkeley sims IP FDDI Token March 9 2006 13 EECS122 Lecture Midterm Review Encapsulation source message segment Ht M datagram Hn Ht M frame M Hl Hn Ht Hl Hn Ht M link physical Hl Hn Ht M Ht M Hn Ht M Hl Hn Ht M application transport network link physical March 9 2006 M Hl Hn Ht M network link physical Nameservers assigned zones of the hierarchical namespace Backup servers available for redundancy Client server interaction on UDP Port 53 but can use TCP if desired DNS client is simple Resolver EECS122 Lecture Midterm Review Authoritative DNS servers organization s DNS servers providing authoritative hostname to IP mappings for organization s servers e g Web and mail Hn Ht M Local DNS Server When a host makes a DNS query query is sent to its local DNS server Can be maintained by organization or service provider Hl Hn Ht M Acts as a proxy forwards query into hierarchy The Local server is not a part of the DNS hierarchy router 14 EECS122 Lecture Midterm Review March 9 2006 EECS122 Lecture Midterm Review Application Protocols How does a name get resolved The Core provides a network service to the hosts Host Host Host Host Network Network Network I don t know but here s who to ask next Recursive query I don t know right now but I ll get back to you HTTP SMTP Iterated query Host 17 Query walks its way up and down the hierarchy 16 Network solutions maintains servers for com TLD Educause for edu TLD Hn Ht fr Top level domain TLD servers responsible for com org net edu etc and all top level country domains uk fr ca jp M switch destination uk Three kinds of DNS servers application transport network link physical M March 9 2006 net Administration divided along the same hierarchy Etc org argus Ethernet mil Hierarchical Namespace Distributed architecture for storing names DNS Routing Protocols e g OSPF March 9 2006 EECS122 Lecture Midterm Review 15 March 9 2006 EECS122 Lecture Midterm Review 18 3 HTTP Electronic Mail HTTP hypertext transfer protocol Three major components outgoing message queue user mailbox Web s application layer protocol client server model client browser that requests receives displays Web objects server Web server sends objects in response to requests HT TP req ues PC running HT t TP res Explorer pon se eq Pr st ue ns e Server T po running HT res Apache Web TP HT server Mac running Navigator Stateless Protocol March 9 2006 HTTP HTTP 1 0 Non Persistent client initiates TCP connection creates socket to server port 80 server accepts TCP connection from client HTTP messages applicationlayer protocol messages exchanged between browser HTTP client and Web server HTTP server TCP connection closed March 9 2006 March 9 2006 HTTP 1 1 Persistent server leaves connection open after sending response subsequent HTTP messages


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Berkeley ELENG 122 - Midterm Review EE 122

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