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Life & Work of Dr. Vinton Cerf and Dr. Robert Kahn | Turing100@Persistent
- 1. www.persistentsys.com
Dr. Vinton Cerf and Dr. Robert Kahn
Their Work and its Impact
R. Venkateswaran
CTO, Persistent Systems Ltd
Email: venki@persistent.co.in
© 2012 Persistent Systems Ltd
- 2. Agenda
Bio of Turing Award Recipients – Dr. Vinton Cerf and Dr.
Robert Kahn
History of the Internet
Early years of Packet Switching
Evolution of Networking protocols over the 40 years
Future architectural options
2
© 2012 Persistent Systems Ltd
- 3. ACKNOWLEDGMENTS:
This presentation has re-used slides and information from
the works of :
• Prof Raj Jain, Washington Univ, St Louis
• Dr. Shivkumar Kalyanaraman, IBM Research, India and
ex-Professor at RPI
• William Stallings – Data & Computer Communication
• Video Interviews of Dr Cerf and Dr Kahn from ACM and
other sources
• Copyrighted material from Robert Zakon’s Internet
Timeline
3
© 2012 Persistent Systems Ltd
- 4. Dr. Vinton Cerf
Widely known as the “Father of the Internet”
Illustrious Career
Elected President of ACM in 2012
Chief Internet Evangelist, Google
Chair, ICANN
Senior VP at MCI, Worldcom
Worked at DARPA
Asst Prof at Stanford University
Awards and Recognition
ACM Turing Award Recipient – 2004
Presidential Medal of Freedom in 2005
Inducted into the Internet Hall of Fame, 2012
Personal:
Shares his birthday with Alan Turing
4 Both he and his wife have a hearing impediment © 2012 Persistent Systems Ltd
- 5. Dr. Robert Kahn
Helped design the Packet-Switched ARPANET
Illustrious Career
President & CEO of CNRI – Corporation for National Research Initiatives
Worked at DARPA
Worked at BBN
Asst Prof at MIT
AT&T Bell Laboratories
Awards and Recognition
ACM Turing Award Recipient – 2004
National Medal of Technology, 1997
Presidential Medal of Freedom, 2005
Inducted into the Internet Hall of Fame, 2012
Personal:
Born on Dec 23, 1938
5
© 2012 Persistent Systems Ltd
- 6. The Internet – 40+ Years
First 20 Years : Internet 1.0
Trusted network used by Defense, Research and Academic Communities
Non-commercial
Popular applications: Email, FTP, Telnet
Next 20 Years : Internet 2.0
Commercial use
Multiple levels of ownership – leads to distrust and Security concerns
Wide range of use: Email, WWW, eCommerce, Multimedia
Key Identifier: IP Address (location, user identity)
Future : Internet 3.0
Centered around Users, Data Objects and Hosts
Service-Oriented
Builtin Security and Mobility support
6
© 2012 Persistent Systems Ltd
- 9. Internetworking Objective
“…both economic and technical
considerations lead us to prefer that the
interface be as simple and reliable as
possible and deal primarily with passing data
between networks using different packet
switching strategies”
V. G. Cerf and R. E. Kahn, 1974
9
© 2012 Persistent Systems Ltd
- 11. Foundation for TCP & IP Protocols - I
Create a nonproprietary universal set of protocols
Standardized – non-Patented, no constraints or controls
Universal Addressing across different networks
Unique identification of hosts in the composite network
Information slices (packets) are transported from one host to another
via the Internetwork
Sequence number facilitates ordering of packets
REF: Cerf, V., and R. Kahn, "A Protocol for Packet Network Intercommunication", IEEE Transactions on
Communications, Vol. COM-22, No. 5, pp 637-648, May 1974
11
© 2012 Persistent Systems Ltd
- 12. Foundation for TCP & IP Protocols - II
Process header (Port) – identify the end process that consumes the
information
Retransmissions and Duplicate detection – addresses packet loss
Flow Control – to limit the number of un-acknowledged packets
Associations between two end processes (“connection”)
Mechanism to set up & release the association
3-way handshake, TCP State machine
REF: Cerf, V., and R. Kahn, "A Protocol for Packet Network Intercommunication", IEEE Transactions on
Communications, Vol. COM-22, No. 5, pp 637-648, May 1974
12
© 2012 Persistent Systems Ltd
- 14. TCP/IP Layered Architecture Model
End
Application Application
to
end Transport Transport
Network Network Network Network
Hop
by Link Link Link Link Link Link
hop
Physical Physical Physical
Host Router Router Host
14
© 2012 Persistent Systems Ltd
- 16. IP : Protocol of choice for Network Layer
Packet-switched datagram network
TCP UDP
IP is the glue (network layer overlay)
Hourglass architecture IP
all hosts and routers run IP
Satellite
Stateless architecture
no flow state maintained in the Ethernet ATM
network
16
© 2012 Persistent Systems Ltd
- 17. IP Network Design Philosophy
Keep the network simple
Simple network devices, intelligent end-systems
Robust and scalable infrastructure
IP Networks offer Best-effort service today
No service guarantees or predictability
Connectionless, datagram model
Each IP packet carries sufficient information for its routing
Hop-by-hop routing – based on destination IP address only
Packets belonging to the same session could be routed differently
Out of sequence packet delivery
Network is application-agnostic – by design
Intelligent end-points, “dumb” network model
17
© 2012 Persistent Systems Ltd
- 18. IP: Minimalist Approach
Dumb network
IP provides minimal functionalities to support connectivity
Addressing, Forwarding, Routing
Smart end system
Transport layer or application performs more sophisticated functionalities
Flow control, Congestion control, Error correction/recovery
Advantages
Accommodate heterogeneous technologies
(Ethernet, modem, satellite, wireless)
Support diverse applications (Email, Telnet, FTP, Usenet)
Decentralized network administration
18
© 2012 Persistent Systems Ltd
- 19. Packet Switching
Courtesy: William Stallings
19
© 2012 Persistent Systems Ltd
- 22. User Datagram Protocol (UDP) – RFC768
UDP – unreliable, datagram-based protocol
Connectionless End-to-End Service
Datagrams may be lost OR delivered out-of-ordered
Error Detection through Checksum (Optional)
Minimal overheads – no state maintained
No Congestion control
Used by Audio/Video Streams, short-transactional applications
22
© 2012 Persistent Systems Ltd
- 23. Transmission Control Protocol (TCP) –
RFC791
Designed to provide Reliable process-to-process communication
service in a multi-network environment
Underlying network unreliable, may deliver bytes out-of-order
Fragmentation handled at the Network Layer
Connection-Oriented: Reliable, Ordered, Stream-based, flow and
congestion controlled, bi-directional
Process Association (State) : combination of IP address and Port
Maintained only at the end hosts, not in the network
Sequence number & Window size facilitate ordering and flow control
23
© 2012 Persistent Systems Ltd
- 24. Evolution of TCP
1984
1975 Nagel’s algorithm
Three-way handshake to reduce overhead 1987
Raymond Tomlinson of small packets; Karn’s algorithm 1990
In SIGCOMM 75 predicts congestion to better estimate 4.3BSD Reno
collapse round-trip time fast retransmit
delayed ACK’s
1983
BSD Unix 4.2 1986 1988
1974 supports TCP/IP Congestion Van Jacobson’s
TCP described by collapse algorithms
Vint Cerf and Bob Kahn observed congestion avoidance
In IEEE Trans Comm 1982 and congestion control
TCP & IP (most implemented in
RFC 793 & 791 4.3BSD Tahoe)
1975 1980 1985 1990
Courtesy: Shiv Kalyanaraman
24
© 2012 Persistent Systems Ltd
- 25. TCP Through the 1990s
1994 1996
T/TCP SACK TCP
(Braden) (Floyd et al)
Transaction Selective
TCP Acknowledgement
1993 1994 1996 1996
TCP Vegas ECN TCP Hoe FACK TCP
(Brakmo et al) (Floyd) Improving TCP (Mathis et al)
real congestion Explicit startup extension to SACK
avoidance Congestion
Notification
1993 1994 1996
Courtesy: Shiv Kalyanaraman
25
© 2012 Persistent Systems Ltd
- 26. TCP Variants :
TCP-Tahoe:
implements the slow start, congestion avoidance, and fast retransmit
algorithms
TCP-Reno:
implements the slow start, congestion avoidance, fast retransmit, and fast
recovery algorithms
Among other implementations are Vegas, NewReno (the most
commonly implemented on webservers today, according to a survey)
and SACK TCP.
26
© 2012 Persistent Systems Ltd
- 28. Key Events in early 90s
Tim-Berners Lee proposed the idea for the World Wide Web
Mosaic – first graphical web browser launched in 1993
First commercial dial-up ISP started its service
Bandwidth doubling every six months
Push for Multimedia applications
Move towards Network Unification
28
© 2012 Persistent Systems Ltd
- 29. Some observations
Demand for broadband access and growth
of bandwidth intensive apps fueling each
other
Applications demanding more from the
underlying network
New applications – VoIP, streaming media
Stringent and often, inflexible requirements
“One-size fits-all” doesn’t work any more BROADBAND
ACCESS
“Dumb network” model may have reached its
limits
BANDWIDTH-
INTENSIVE APPS
Networks must provide a more predictable service
29
© 2012 Persistent Systems Ltd
- 30. Growth of the Internet
Copyright: http://www.zakon.org/robert/internet/timeline/
30 Used with Permission © 2012 Persistent Systems Ltd
- 31. Growth of the Internet
Copyright: http://www.zakon.org/robert/internet/timeline/
31 Used with Permission © 2012 Persistent Systems Ltd
- 32. Applications: network requirements
High
Streaming Interactive
Video Video Conferencing
E-mail with
Attachments
Voice
Requirements
Internet/
Bandwidth
intranet
E-commerce
Text ERP
e-mail
Terminal Mode
Transactions
Low
Low Latency Sensitivity High
32
© 2012 Persistent Systems Ltd
- 33. Evolution of Multi Service Networks
As Internet Usage increased, an evolved Next Generation Network
(NGN) architecture became important
Characteristics of the NGN
One common network capable of handling data, voice and video
communications
Packet-Switched Network -- “Data friendly” transport and switching
infrastructure
Flexible services control elements to enable voice communications and
support data and QoS in the future
Voice parity with the PSTN in terms of features and quality
Source: http://tmdenton.com/pub/bellheads.pdf
33
© 2012 Persistent Systems Ltd
- 35. Ideological Differences
BellHeads NetHeads
Circuit-switched Telco background IP-based Internet background
Align with Formal ITU Standards Align with Open IETF Standards
Closed Communities Open and Free Community
Believe in Guaranteed QoS Believe in Best-Effort Services
Expect to get Paid for delivering service Expect services to be Cheap/Free
Voice: Per-minute charging with Voice: Just another App on the Packet
settlement between carriers switched network and is FREE
Dumb end-points, Smart Networks Dumb networks, Smart end-points
Wish to Control the Future of the Watch the Network Evolve organically
Network
Prefer Strong Regulatory Environment Open and Unregulated Playing Field
35
© 2012 Persistent Systems Ltd
- 36. www.persistentsys.com
Asynchronous Transfer Mode (ATM)
Networks
BellHead view of NGN
© 2012 Persistent Systems Ltd
- 37. Bellheads view of NGN – ATM Networks
Packet switched network, but connection-oriented
Fixed size (53-byte) packets called “CELLS”
Path setup from source to destination before data transfer
(“connection”)
All Cells of a connection traverse the same path
In the network, cells are “switched” based on the fixed header (VPI/VCI)
Using Admission Control policies, network can guarantee QoS for
various applications
37 Could support extremely high speeds (OC-192 or ~10Gbps)
© 2012 Persistent Systems Ltd
- 40. Per-packet processing in an IP Router
1. Accept packet arriving on an incoming link.
2. Lookup packet destination address in the forwarding table, to
identify outgoing port(s) – Longest Prefix Match
3. Manipulate packet header: e.g., decrement TTL, update
header checksum.
4. Send (switch) packet to the outgoing port(s).
5. Classify and buffer packet in the queue.
6. Transmit packet onto outgoing link.
Courtesy: Shiv Kalyanaraman
40
© 2012 Persistent Systems Ltd
- 41. Lookup Rates Required
Optical Line Rate 40 Byte Pkts Lookup
Interface (Gbps) (Mpps) Rates (ns)
OC-12 0.622 1.94 515
OC-48 2.5 7.81 128
OC-192 10.0 31.25 33
OC-768 40.0 125 8
41
© 2012 Persistent Systems Ltd
- 42. Routing Table Size
Source: Geoff Huston, Internet Protocol Journal, Vol 4, No. 1
42
© 2012 Persistent Systems Ltd
- 45. Routing vs Switching
Routing – based on address lookup and longest prefix match
Search and compare operation
Complexity : O(log2 N)
Switching – based on a circuit number (pre-set)
Indexing operation
Complexity : O(1)
Extremely well-suited for High-speed Networks with Large Address Spaces
45
© 2012 Persistent Systems Ltd
- 46. 1996: Ipsilon’s IP Switching Concept
Hybrid: IP routing (control plane) + ATM switching (data plane)
Courtesy: Shiv Kalyanaraman
46
© 2012 Persistent Systems Ltd
- 50. MPLS: Best of Both Worlds
PACKET CIRCUIT
HYBRID SWITCHING
ROUTING
IP MPLS ATM TDM
+IP
Courtesy: Shiv Kalyanaraman
50
© 2012 Persistent Systems Ltd
- 52. MPLS – Multiprotocol Label Switching
Introduces a new fixed-length header (label) for the IP packet payload
MPLS is considered Layer 2.5
Separates forwarding information (label) from IP header
Easy to implement this in hardware
Routing at the edge, switching at the core
MPLS label introduced at the ingress edge
Core routers use these labels to switch packets
Label removed at the egress edge router
Pre-defined paths for switching MPLS packets
Offline path creation – eliminates path computation overheads
MPLS header supports CoS markings
52
© 2012 Persistent Systems Ltd
- 53. MPLS Header
Label (20-bits) CoS S TTL
L2 Header MPLS Header IP Packet
32-bits
Fields
Label
Experimental (CoS)
Stacking bit
Time to live
IP packet is encapsulated at an Entry into MPLS domain
IP packet is de-encapsulated at exit from MPLS domain
53
© 2012 Persistent Systems Ltd
- 54. MPLS – Main Ideas
Separate forwarding information (label) from the content of IP header
Single forwarding paradigm (label swapping) - multiple routing
paradigms
Multiple link-specific realizations of the label swapping forwarding
paradigm
Flexibility of forming Forwarding Equivalence Classes (FECs)
Forwarding hierarchy via label stacking
54
© 2012 Persistent Systems Ltd
- 55. MPLS Terminology
Connection Table
In Out Label
IP 25 (port, label) (port, label) Operation
Port 1 Port 2
(1, 22) (2, 17) Swap
(1, 24) (3, 17) Swap
IP 19 (1, 25) (4, 19) Swap
Port 3 Port 4
(2, 23) (3, 12) Swap
Label Swapping
Connection table maintains mappings
Exact match lookup
Input (port, label) determines:
Label operation
Output (port, label)
Same forwarding algorithm used in Frame Relay and ATM
Courtesy: Rahul Aggarwal
55
© 2012 Persistent Systems Ltd
- 56. MPLS Terminology
Egress
LSR
Ingress
New York
LSR Transit
San LSR Transit
Francisco LSR
LSP
Ingress LSR (“head-end LSR”)
Examines inbound IP packets and assigns them to an FEC
Generates MPLS header and assigns initial label
Transit LSR
Forwards MPLS packets using label swapping
Egress LSR (“tail-end LSR”)
56
Removes the MPLS header Courtesy: Rahul Aggarwal
© 2012 Persistent Systems Ltd
- 57. MPLS Forwarding Model
Source Egress
Ingress LSR Paris
LSR
Rome
Ingress LSR determines FEC and assigns a label
Forwards Paris traffic on the Green LSP
Forwards Rome traffic on the Blue LSP
Traffic is label swapped at each transit LSR
Egress LSR
Removes MPLS header
Forwards packet based on destination address Courtesy: Rahul Aggarwal
57
© 2012 Persistent Systems Ltd
- 58. MPLS Forwarding vs. IP Routing
Source Destination
IP Routing Domain
Examine IP header Examine IP header Examine IP header Examine IP header
Assign to FEC Assign to FEC Assign to FEC Assign to FEC
Forward Forward Forward Forward
Ingress Egress
Source Destination
LSR MPLS Domain LSR
Examine IP header Examine IP header
Assign to FEC Label swap Label swap Assign to FEC
Forward Forward Forward Forward
Courtesy: Rahul Aggarwal
58
© 2012 Persistent Systems Ltd
- 59. MPLS Forwarding Example
MPLS Table
In Out 134.5.6.1
(2, 84) (6, 0)
134.5.1.5
2 6
Egress Routing Table
Destination Next Hop
200.3.2.7 2
134.5/16 134.5.6.1
3 200.3.2/24 200.3.2.1
Ingress Routing Table 1 2 3 5
Destination Next Hop 200.3.2.7
134.5/16 (2, 84)
200.3.2/24 (3, 99)
MPLS Table MPLS Table 200.3.2.1 200.3.2.7
In Out In Out
(1, 99) (2, 56) (3, 56) (5, 0)
Courtesy: Rahul Aggarwal
59
© 2012 Persistent Systems Ltd
- 60. MPLS - Summary
MPLS forwarding algorithm is simpler than IP forwarding algorithm
Fixed size header vs variable sized header
Enables more functionality than could be provided with the IP
forwarding algorithm
Eg. All packets traverse the same path through the domain
MPLS is an architectural shift
Enables many applications; difficult to foresee all of them
Most Service Providers today are moving towards MPLS deployment
Reduce cost, simplify operations, introduce high-value services
MPLS is also evolving
ER-MPLS, MPLS-TE etc.
60
© 2012 Persistent Systems Ltd
- 62. Some challenges with today’s Internet
Support for Mobility with TCP/IP not efficient
Security issues – viruses, spams, bots, DDOS attacks, hacks
Internet was designed with “friendly” users in mind
Multi-homing not well supported by TCP/IP
Change in IP Interface results in service disruption
Applications are designed to work well *only* if round-trip delays are
small
TCP/IP expects most parts of the network to be interconnected
Routing protocols are becoming complex
Courtesy: Raj Jain
62 Routers are becoming expensive
© 2012 Persistent Systems Ltd
- 63. Challenges….
Network-centric (“Where”) approach not optimal for various applications
People-centric – “Who”
Content-centric – “What”
IP Address correlates Identity and Location
This may neither be necessary nor desirable
Courtesy: Raj Jain
63
© 2012 Persistent Systems Ltd
- 64. Future Research
Delay Tolerant Network Architecture
Content-Centric Networks
Software Defined Network (SDN)
Network Virtualization paradigm
64
© 2012 Persistent Systems Ltd
- 66. Delay Tolerant Networks (DTN)
DTNs Characterized by
Intermittent Connectivity
Extremely Long Delays
Asymmetric Data Rates
High Error Rates
Addressed using a Store-and-Forward Message Switching paradigm
IETF RFC 4838
66
© 2012 Persistent Systems Ltd
- 67. Delay Tolerant Network – Overlay Arch
Source: http://www.cs.rice.edu/~scrosby/TA/comp620-s05/papers/F03.pdf
67
© 2012 Persistent Systems Ltd
- 70. Content Centric Networks
Strategy – Figuring out the best path to deliver the content
Dynamic optimization
Security – Ensure content access only to authorized users
Interest Packet – used to request a specific content
Data Packet – contains the specific content
Mechanisms to forward an Interest packet towards available content
store
70
© 2012 Persistent Systems Ltd
- 72. SDN Architecture
App App App App
Open API
Network Operating System
Open Interface
to Hardware
(OpenFlow)
Openflow Openflow
Firmware Firmware
Packet-Forwarding Packet-Forwarding
Hardware Hardware
Openflow Openflow
Firmware Firmware
Packet-Forwarding Packet-Forwarding
Hardware Hardware
Courtesy: Matt Davy
72
© 2012 Persistent Systems Ltd
- 73. Analogy with Computer Industry
Computer Industry Network Industry
Apps Apps Apps Apps Apps Apps
Network
Windows Linux FreeBSD NOX Beacon
OS
Virtualization Virtualization
Openflow
x86
Courtesy: Matt Davy
73
© 2012 Persistent Systems Ltd
- 77. References
1. Prof Raj Jain’s home page - http://www.cse.wustl.edu/~jain/
2. Dr Shivkumar Kalyanaraman’s lectures -
http://www.ecse.rpi.edu/Homepages/koushik/shivkuma-
teaching/video_index.html
3. Hobbes’ Internet Timeline - http://www.zakon.org/robert/internet/timeline/
4. ACM Turing Award Video Lecture of Dr Cerf & Dr Kahn -
http://amturing.acm.org/vp/cerf_1083211.cfm
5. Vint Cerf & Bob Kahn’s seminal paper on Protocol for Packet Network
Intercommunication
http://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf
6. Relevant RFCs from IETF - www.ietf.org
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© 2012 Persistent Systems Ltd