1. ECE544: Communication Networks-II, Spring 2016
Prof. D. Raychaudhuri
Lecture 1
Includes teaching materials from L. Peterson & R. Govindan

2. Today’s Lecture Administrative matters Course Overview
topics covered
design & prototyping projects
Introduction to networking

3. Class Structure Friday 3:45-6:30pm Lecture format Two 80 min sessions
Slides, Board, …
Interactive
Two 80 min sessions
with a 10 min break in between

4. Contact Information
Instructor:
Prof. D. Raychaudhuri
Office Hours: by appt, WINLAB Tech Center or Core 501
Project TA: Francesco Bronzino
Office hours: by appt

5. Class Resources Web page: http://www.winlab.rutgers.edu/comnet2
Mailing list:
Sign up for mailing list at:

6. Course Readings Textbook (required, to be used for ~60% material)
Peterson & Davie, “Computer Networks: A Systems Approach”, Morgan Kaufman, 4th or 5th editions
Handouts posted to course website
Research papers in networking
to be distributed either online or in class
collection of classical and topical research
~10 papers and standards documents
required reading to supplement text book overview

7. Course Grading Class participation & homework: 5%
Brief in-class presentations
Assigned homework from textbook
Midterm (25%) and Final (35%)
Open book, 1 page of notes permitted; includes both descriptive and numerical problems
Design & Prototyping Assignments: 35%
network architecture paper 10%
protocol project & report 25%
No makeup exams, no extra credit work

8. Student Commitments Keep up with your reading
read applicable text book chapter and distributed papers/RFC’s before and after each class
Sharpen your programming skills
study C/C++ & Unix programming as needed and work on simple programming exercises early in the semester
Work independently (except group projects)
no “collaboration” of any sort
Turn in assignments on time
Make sure assignments are gradable
follow project and program submission rules

9. Prerequisites Curricular prerequisites Skills
Computer Networks I or equivalent
General communications and computer architecture/OS background
Skills
C/C++ programming
significant programming project
use of design and analysis tools

10. Course Topics Software defined networks Introduction
Network security
Transport layer
Higher-layer protocols
Hardware issues
Case studies and research topics
Content networks
Cloud computing services
future Internet architecture
Introduction
Network Principles
Shared Media/MAC
Packet switching
IP Basics
IP Advanced
Mobility Protocols
-- mid-term
Describe each topic broadly: what it covers: give examples, make it interesting. Routing: (examples of ad-hoc routing, examples of synchronization, how you can encode policy in routing), Multicast: (tree construction algorithms for conferencing and other applications), queueing and congestion control/avoidance (big problem of packet losses, recovery latency): how router mechanisms can improve this: what does traffic look like etc.

11. Projects Warm-up Projects Network architecture paper
- C/C++ programming exercises
- Unix sockets, etc.
- simple link protocols
Network software project
- new routing protocol
- software platform provided
- student teams will write competing protocol specs
- meetings to specify “standard”
- group demo & inter-op demo
Network architecture paper
- top-down design
- requirements
- specifications
- system analysis
- report
Describe each topic broadly: what it covers: give examples, make it interesting. Routing: (examples of ad-hoc routing, examples of synchronization, how you can encode policy in routing), Multicast: (tree construction algorithms for conferencing and other applications), queueing and congestion control/avoidance (big problem of packet losses, recovery latency): how router mechanisms can improve this: what does traffic look like etc.

12. What is the problem? Applications The Global Network Scale Technology
Holy grail: unified theory of networking: one collection of mechanisms that supports a variety of applications (give application examples: TV/video to the home etc.), that scales to every home (5 billion people, one computer per person, people talking of even bigger networks), keeps up with technological progress
What do we mean by “the network”? Talk about global network structure later. But at this point, introduce the notions of hosts, routers, links. Mention that what we usually mean by “the network” is the collection of links and routers, together with the transmission algorithms running at the host.
Technology
Robustness

13. Application Considerations
Variety of current and future applications to be supported by the network
Content Delivery
Vehicular Networks
What the application delivers to the network? What the application needs from the network: a target data rate, target latencies etc. Talk about each one of these and how it affects network design. What kinds of tradeoff can we do? How traffic burstiness affects the aggregate characteristics; in turn, how are applications affected by delay and loss
Cloud Services
Mobile Data
(cellular, hetnet)
Emergency Networks
Internet-of-Things

14. Application Considerations
Application input to network
traffic data rate
traffic pattern (bursty or constant bit rate)
traffic target (multipoint or single destination, mobile or fixed)
Network service delivered to application
delay sensitivity
loss sensitivity
Mobility, location, multicast, etc.
What the application delivers to the network? What the application needs from the network: a target data rate, target latencies etc. Talk about each one of these and how it affects network design. What kinds of tradeoff can we do? How traffic burstiness affects the aggregate characteristics; in turn, how are applications affected by delay and loss

15. Multimedia and Video Applications
The classic Internet App: voice, video, data; streaming BW, latency, ..
Circa 1990
~2010
~2013

16. Application Considerations (IoT)
Large # devices (~100B+), low power, bursty data, ..

17. Application Considerations (Data Centers, Cloud)
High traffic volume, latency sensitive, …

18. Reliable File Transfer
Loss sensitive
Not delay sensitive relative to round trip times
Point-to-point or multipoint
Bursty
Eg. FTP. Cannot tolerate loss, can tolerate modest amounts of delay, not inherently bursty, but because of some control algorithms… Analogy of humans transferring (taking dictation). Other characteristics: large packet sizes etc.

19. Remote Login Loss sensitive Delay sensitive Bursty Point to point
subject to interactive constraints
can tolerate up to several hundreds of milliseconds
Bursty
Point to point

20. Network Audio Relatively low bandwidth Delay variance sensitive
Digitized samples, packetized
Delay variance sensitive
Loss tolerant
Possibly multipoint, long duration sessions
natural limit to number of simultaneous senders

21. Network Video High bandwidth Compressed video, bursty
Loss tolerance function of compression
Delay tolerance a function of interactivity
Possibly multipoint
Larger number of simultaneous sources

22. Web Transactional traffic Loss tolerant Delay sensitive
short requests, possibly large responses
Loss tolerant
Delay sensitive
human interactivity
Point-to-point (multipoint is asynchronous)

23. What is….
The Global Network
Structure
Metrics
Failure modes
Functions

24. Network Structure Servers, Data Centers National/Global
Networks, Backbones
Regional
Networks, ISP
Routers,
Switches
Local/Access
Networks
Links, LAN
Nodes,
Hosts, CPE

25. Network Topologies

26. Network Metrics Bandwidth Delay Delay-Bandwidth product
transmission capacity
Delay
queueing delay
propagation delay (limited by c)
Delay-Bandwidth product
important for control algorithms

27. Bandwidth versus Latency
Relative importance
1-byte: 1ms vs 100ms dominates 1Mbps vs 100Mbps
25MB: 1Mbps vs 100Mbps dominates 1ms vs 100ms
Infinite bandwidth
RTT dominates
Throughput = TransferSize / TransferTime
TransferTime = RTT + 1/Bandwidth x TransferSize
1-MB file to 1-Gbps link as 1-KB packet to 1-Mbps link

28. Delay x Bandwidth Product
Amount of data “in flight” or “in the pipe”
Example: 100ms x 45Mbps = 560KB

29. 10,000
5000
2000
1000
500
1-MB object, 1.5-Mbps link
200
1-MB object, 10-Mbps link
Perceived latency (ms)
100
2-KB object, 1.5-Mbps link
2-KB object, 10-Mbps link 50
1-byte object, 1.5-Mbps link
1-byte object, 10-Mbps link 20 10 5 2 1 10
100 R
TT (ms)
Chapter 1, Figure 1.20

30. Network Failures Packet loss Node or link failures
queue overflows
line noise
Node or link failures
Routing transients or failures

31. Statistical Multiplexing Gain
1 Mbps link; users require 0.1 Mbps when transmitting; users active only 10% of the time.
Circuit switching: can support 10 users
Packet switching: with 35 users, probability that >=10 are transmitting at the same time =

32. Back in the old days.. bw
Time

33. Then came TDM..
mux
demux

34. Logical network view

35. Packet switching (Internet)

36. Packet Switching Interleave packets from different sources
Efficient: resources used on demand
statistical multiplexing
General
multiple types of applications
Accommodates bursty traffic

37. Characteristics of Packet Switching
Store and forward
packets are self contained units
can use alternate paths - reordering
Contention
congestion
delay

38. Protocols On top of a packet switched network, need
Set of rules governing communication between network elements (applications, hosts, routers)
Protocols define:
format and order of messages
actions taken on receipt of a message

39. Protocols (contd.) Building blocks of a network architecture
Each protocol object has two different interfaces
service interface: operations on this protocol
peer-to-peer interface: messages exchanged with peer
Term “protocol” is overloaded
specification of peer-to-peer interface
module that implements this interface

40. Layering Layering: technique to simplify complex systems
Teleconferencing
User A
User B
Peers
Application
Transport
Network
Link
Host
Host
Layering: technique to simplify complex systems

41. Layering

42. 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)

43. Packet Headers Packet Headers can contain:
- addresses, flow ID, pkt type, service type, error checks, QoS, …
Layer 2 hdr
Layer 3 hdr
Trailer
Layer 4 hdr
Data
“Encapsulation”

44. ISO Architecture End host End host Application Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Network
Network
Data link
Data link
Data link
Data link
Physical
Physical
Physical
Physical
One or more nodes
within the network

45. Internet Architecture
Defined by Internet Engineering Task Force (IETF)
Hourglass Design
Application vs Application Protocol (FTP, HTTP) …
FTP
HTTP NV
TFTP
TCP
UDP IP
NET 1 2 n

46. Internet Reference Model
IP is the “narrow waist” of the Internet
Supports many different links below and apps above.
Examples of common protocols in each layer
SMTP HTTP RTP DNS
Ethernet 3G
Cable DSL
7 Application
TCP UDP
4 Transport IP
3 Internet
2/1 Link

47. Layering General Issues
Reliability
Flow control
Fragmentation
Multiplexing
Connection setup (handshaking)
Addressing/naming (locating peers)

48. Example: Transport layer
First end-to-end layer
End-to-end state
May provide reliability, flow and congestion control

49. Example: Network Layer
Point-to-point communication
Network and host addressing
Routing

50. Encapsulation HTTP HTTP HTTP HTTP TCP HTTP TCP HTTP TCP TCP IP TCP
802.11 IP
TCP
HTTP
802.11 IP
TCP
HTTP
802.11
802.11
(Wire)
802.11 IP
TCP
HTTP

51. Demultiplexing SMTP HTTP DNS TCP UDP IP ARP Ethernet Host
Incoming messages must be passed to the protocol it uses.
Done with demultiplexing keys in the headers
SMTP
HTTP
DNS
TCP
UDP IP
ARP
Ethernet
Host
TCP port number
IP protocol field
Ethertype value
Ethernet IP
TCP
HTTP
Incoming message

52. Inter-Process Communication
Turn host-to-host connectivity into process-to-process communication.
Fill gap between what applications expect and what the underlying technology provides.
Host
Application
Channel

53. Network-Application Interface
Defines how apps use the network
Lets apps talk to each other via hosts;
hide the details of the network
Sockets let apps attach to the local network at different
ports
App
host
Socket,
Port #1
Port #2
ISP

54. IPC Abstractions Stream-Based Request/Reply video: sequence of frames
1/4 NTSC = 352x240 pixels
(352 x 240 x 24)/8=247.5KB
30 fps = 7500KBps = 60Mbps
video applications
on-demand video
video conferencing
Request/Reply
distributed file systems
digital libraries (web)

55. Interfaces Chapter 1, Figure 1.10 Host 1 Host 2 Service High-level
object
interface
object
Protocol
Protocol
Peer-to-peer
interface
Chapter 1, Figure 1.10

56. Interfaces (contd.)

57. Interfaces (contd.)
Chapter 1, Figure 17

58. Protocol Machinery Protocol Graph
most peer-to-peer communication is indirect
peer-to-peer is direct only at hardware level
Host 1
Host 2
Digital
File
Digital
Video
File
Video
library
library
application
application
application
application
application
application
RRP
MSP
RRP
MSP
HHP
HHP
Chapter 1, Figure 1.11

59. Machinery (cont) Multiplexing and Demultiplexing (demux key)
Encapsulation (header/body)
Host 1
Host 2
Application
Application
program
program
Data
Data
RRP
RRP
RRP
Data
RRP
Data
HHP
HHP
HHP
RRP
Data
Chapter 1, Figure 1.12

60. Socket Basics

61. Socket API Primitive Meaning SOCKET
Create a new communication endpoint
BIND
Associate a local address with a socket
LISTEN
Announce willingness to accept connections; give queue size
ACCEPT
Passively establish an incoming connection
CONNECT
Actively attempt to establish a connection
SEND
Send some data over the connection
RECEIVE
Receive some data from the connection
CLOSE
Release the connection

62. Client & Server Program Outline
socket()
//make socket
//make a socket
getaddrinfo()
//server and port name
//for port on this host //
blind()
//associate port with socket
connect()
//connect to server [block]
listen()
//prepare to accept connections …
accept()
//wait for a connection [block]
send()
//send request
recv()
//wait for request
//await reply [block]
//do something with data!
//send the reply
close()
//done, disconnect
//eventually disconnect

63. Using Sockets Client (host 1) Time Server (host 2) 1: socket 2: bind
connect
3: listen
4: accept*
5: connect*
request
6: receive*
7: send
8: receive*
reply
9: send
10: close
disconnect
10: close
*=call blocks

64. Network Architecture
Goal is to design a complete network solution that meets service requirements and cost constraints
Design space includes
Application platform & software
Network topology
Core technologies
Protocols
Traffic engineering
Cost estimation

65. Concept Example 1: Sensor Nets
Compute & Storage
Servers
Pervasive
Application
Agents
User interfaces for
information & control
Sensor net/IP gateway
Mobile Internet (IP-based)
Overlay Sensor Network Infrastructure
3G/4G
BTS GW
ZigBee,
UWB, etc.
Relay Node
Ad-Hoc Sensor Net A
Sensor/
Actuator
Ad-Hoc Sensor Net B
Virtualized Physical World
Object or Event

66. Concept Example 2: Infostations
Networks to support opportunistic delivery of data to mobiles
Internet
Mobile DTN Router
Roadway Sensors
Ad-Hoc
Network
Opportunistic
High-Speed Link
(MB/s)
Mobile P2P User
Static DTN
Router

67. Designing a Network Identify basic service requirements
transport service(s)
bit-rates to be supported
network API
# of users
terminal type (fixed, portable, etc.)
Outline network topology
access network type (wired/wireless, span, etc.)
core network if any (node locations, span, etc.)

68. Requirements (contd.) List additional service and network features
QoS, video/audio, etc.
special routing (mcast, broadcast,..)
mobility
availability
reliability
security/authentication
Rough system capacity (Mbps) and cost estimates ($/MB or $/user/mo)

69. Requirements Analysis
Summary table listing key requirements
Transport services
CBR, VBR-rt,..
Bit rate
Mbps
# of users
~1000’s per access network
Terminal type
portable/mobile, fixed wireless
Topology
hierarchical, access/core
QoS features
selectable BW, stream support
99.9%
Availability
99.99%
Reliability
Security features
mobile authentication, on-air encryption
Cost
$0.1/MB or $50/mo/user

70. Network Components Key hardware components of a network
NIC ~10, 100, 155, 622, 1000 Mbps
shared media channels (Ethernet, HFC, wireless, satellite, ..) ~Mbps
point-to-point links (DSL, CAT-5, microwave, fiber,..)
switches (Ethernet, ATM, MPLS/IP) ~ Gbps -Tbps
routers (IP) ~Mbps - Gbps

71. Network Components Key software components of a network
CPE/Terminal OS & drivers
Application interface – “socket” spec
Transport layer protocol
Network layer protocol (at client)
Network layer protocol (at network elements)
Network management system
Any additional directories or network services

72. High-Level Design
Select network topology based on geographic, capacity, reliability, etc.
Partition into access network, core network, etc. as required
Assign network hardware components to each subnetwork based on service and QoS requirements
Define service API and protocol stacks
Analyze network performance & cost and iterate until requirements are met

73. High Level Design Access Net Users (#, density, mobility)
Technology choice
(e.g. MPLS optical)
Mbps needed?
Technology choice
(e.g. IP router)
Access Net
Physical
Span?
Technology choice
(e.g. Ethernet SW)
bps
Pkt size
Burst statistics
Stream parameters
Technology choice
(e.g n)
bps/sq-m for wireless access
Users
(#, density, mobility)

74. Today’s Homework Peterson & Davie, Chap 1 (4th ed) -1.3 -1.15 -1.17
-1.23
-1.28