1 Goals and Objectives Understand state-of-the-art in network protocols, architectures, and...
-
Upload
arline-bradford -
Category
Documents
-
view
219 -
download
0
Transcript of 1 Goals and Objectives Understand state-of-the-art in network protocols, architectures, and...
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
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
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
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
Back in the Old Days…
6
Packet Switching (Internet)
Packets
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
Internet[work]
Internet[work]
• A collection of interconnected networks
• Host: network endpoints (computer, PDA, light switch, …)
• Router: node that connects networks
• Internet vs. internet
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
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
How To Find Nodes?
Internet
Computer 1 Computer 2
Need naming and routing
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
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
Routing
R
R
R
RRH
H
H
H
R
RH
R
Routers send packet towards
destination
H: Hosts
R: Routers
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
Meeting Application Demands
• Reliability• Corruption• Lost packets
• Flow and congestion control
• Fragmentation
• In-order delivery
• Etc. …
17
What if the Data gets Corrupted?
InternetGET windex.htmlGET index.html
Solution: Add a checksum
Problem: Data Corruption
0,9 9 6,7,8 21 4,5 7 1,2,3 6X
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
What if the Data gets Lost?
InternetGET index.html
Problem: Lost Data
InternetGET index.html
Solution: Timeout and Retransmit
GET index.htmlGET index.html
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
Solution: Add Sequence Numbers
Problem: Out of Order
What if the Data is Out of Order?
GETx.htindeml
GET x.htindeml
GET index.html
ml 4 inde 2 x.ht 3 GET 1
22
Lots of Functions Needed
• Link
• Multiplexing
• Routing
• Addressing/naming (locating peers)
• Reliability
• Flow control
• Fragmentation
• Etc. …
23
What is Layering?
• Modular approach to network functionality
• Example:
Link hardware
Host-to-host connectivity
Application-to-application channels
Application
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
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)
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
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