1. 1 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

2. 2 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, …

3. 3 Lecture Topics Traditional Layering Internet architecture Routing (IP) Transport (TCP) Queue management (FQ, RED) Naming (DNS) Recent Topics Multicast Mobility/wireless Active networks QoS Network measurement Overlay networks P2P applications Datacenter networking Italics topics on Quiz #2

4. 4 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, …

5. 5 Back in the Old Days…

6. 6 Packet Switching (Internet) Packets

7. 7 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

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

9. 9 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

10. 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

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

12. 12 Naming What’s the IP address for www.cmu.edu? It is 128.2.11.43 Translates human readable names to logical endpoints Local DNS ServerComputer 1

13. 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 i3, DOA, etc. 13

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

15. 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, i3, DTN, DOA, policy- aware switching, network measurement 15

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

17. 17 What if the Data gets Corrupted? Internet GET windex.htmlGET index.html Solution: Add a checksum Problem: Data Corruption 0,996,7,8214,571,2,36 X

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

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

20. 20 Problem: Packet size Solution: Fragment data across packets What if the Data Doesn’t Fit? On Ethernet, max IP packet is 1.5kbytes Typical web page is 10kbytes GETindex.html GET index.html

21. 21 Solution: Add Sequence Numbers Problem: Out of Order What if the Data is Out of Order? GETx.htindeml GET x.htindeml GET index.html ml4inde2x.ht3GET1

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

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

24. 24 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

25. 25 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)

26. 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 E2E assumptions questioned and revised 26

27. 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