Goals and Objectives Understand stateoftheart in network protocols

Goals and Objectives • Understand state-of-the-art in network protocols, architectures, and applications • Process of networking research • Constraints and thought processes for networking research • Problem Formulation—Approach—Analysis— Results • Different from undergraduate networking (EECS 122) • i. e. , training network programmers vs. training network researchers 1

Class Topic Coverage • Little on physical and data link layer • Little on undergraduate material • Supposedly you already know this, though some revisiting/overlap is unavoidable • Focus on the why, not the what • Focus on network-to-application layer • We dealt with: • Protocol rules and algorithms, tradeoffs, rationale • Routing, transport, DNS resolution, … • Network extensions and next generation architecture • Wireless, mobile, sensor, … 2

Lecture Topics • • • Traditional Layering Internet architecture Routing (IP) Transport (TCP) Queue management (FQ, RED) Naming (DNS) • • Recent Topics Multicast Mobility/wireless Active networks Qo. S Network measurement Overlay networks P 2 P applications Datacenter networking Italics topics on Quiz #2 3

What is the Objective of Networking? • Communication between applications on different computers • Must understand application needs/demands • Traffic data rate, pattern (bursty or constant bit rate), target (multipoint or single destination, mobile or fixed) • Delay and loss sensitivity • Other application-support services • Overlays, Active Networks, Data-oriented, … 4

Back in the Old Days… 5

Packet Switching (Internet) Packets 6

Packet Switching • Interleave packets from different sources • Statistical multiplexing to use resources on demand • Supports multiple applications types • Accommodates bursty traffic via queues • Store and forward • Packets are self contained units • Can use alternate paths – reordering • Effects of contention: congestion and delay • Semester readings on Fair Queuing, Router Design, Network Topology and Network Measurement 7

Internet[work] • A collection of interconnected networks • Host: network endpoints (computer, PDA, light switch, …) • Router: node that connects networks • Internet vs. internet Internet[work] 8

Challenge • Many differences between networks • • • Address formats Performance – bandwidth/latency Packet size Loss rate/pattern/handling Routing • How to translate between various network technologies? • Gateways 9

Extensions to the Network • New kinds of networks within the Internet • • • Mobile Wireless Sensor Delay Tolerant Content Distribution/Data Oriented Networks • Semester readings on Roofnet, Ad hoc and sensor net routing, DTNs, CDNs, DOT, etc. 10

How To Find Nodes? Internet Computer 1 Computer 2 Need naming and routing 11

Naming What’s the IP address for www. cmu. edu? It is 128. 2. 11. 43 Computer 1 Local DNS Server Translates human readable names to logical endpoints 12

Extensions to the Network Architecture • Naming • • DNS as an Overlay Network Problems with Host-to-IP Address bindings Problems with Service-to-Host bindings Solutions based on the idea of an extra level of indirection: flat identifiers plus resolution based on DHT lookup • Semester readings on DNS and on flat names and DHTs in the context of i 3, DOA, etc. 13

Routing Routers send packet towards destination H R R R H H: Hosts R: Routers 14

Extensions to the Network Architecture • Forwarding • Problems with Internet routing • Beyond point-to-point routing: multicast, mobility, alternative schemes and metrics for wireless/sensor nets, delay tolerant nets, etc. • Indirection schemes and intermediaries (“performance enhancing proxies”) to implement new forms of forwarding • Semester readings on Internet topology, multicast, wireless, i 3, DTN, DOA, policyaware switching, network measurement 15

Meeting Application Demands • Reliability • Corruption • Lost packets • • Flow and congestion control Fragmentation In-order delivery Etc. … 16

What if the Data gets Corrupted? Problem: Data Corruption GET index. html Internet GET windex. html Solution: Add a checksum 0, 9 9 6, 7, 8 21 X 4, 5 7 1, 2, 3 6 17

What if Network is Overloaded? Problem: Network Overload Solution: Buffering and Congestion Control • Short bursts: buffer • What if buffer overflows? • Packets dropped • Sender adjusts rate until load = resources “congestion control” 18

What if the Data gets Lost? Problem: Lost Data GET index. html Internet Solution: Timeout and Retransmit GET index. html Internet GET index. html 19

What if the Data Doesn’t Fit? Problem: Packet size • On Ethernet, max IP packet is 1. 5 kbytes • Typical web page is 10 kbytes Solution: Fragment data across packets ml x. ht inde GET index. html 20

What if the Data is Out of Order? Problem: Out of Order ml inde x. ht GET x. htindeml Solution: Add Sequence Numbers ml 4 inde 2 x. ht 3 GET 1 GET index. html 21

Lots of Functions Needed • • Link Multiplexing Routing Addressing/naming (locating peers) Reliability Flow control Fragmentation Etc. … 22

What is Layering? • Modular approach to network functionality • Example: Application-to-application channels Host-to-host connectivity Link hardware 23

Protocols • Module in layered structure • Set of rules governing communication between network elements (applications, hosts, routers) • Protocols define: • Interface to higher layers (API) • Interface to peer • Format and order of messages • Actions taken on receipt of a message 24

Layering Characteristics • Each layer relies on services from layer below and exports services to layer above • Interface defines interaction • Hides implementation - layers can change without disturbing other layers (black box) 25

Application-Oriented Networking • All kinds of new application-specific routing and transport layers • • • Sensor network dissemination protocols Content distribution/data oriented networks Overlay networks Active networks Middleboxes/”Performance Enhancing Proxies” • Layering and E 2 E assumptions questioned and revised 26

Quo Vadis Networking? • GENI: new architecture for Next Generation • New naming and forwarding as foundation • Security and authenticity from first principles • Experimentation in upper layers, e. g. , DTN • Refocus from wide-area to local-area • • Unified telephony and data, wired/wireless Datacenters for web and batch parallel apps O(10, 000) node DC and enterprise networks New addressing, transport opportunities 27