Emerging Internet Technologies

1
Emerging Internet Technologies

• Harish Sethu
• Department of Electrical and Computer Engineering
• Drexel University

2
Introduction and History

• More rapid growth than any medium in history
• New applications in education, business and
  medicine
• Impact on entertainment, politics and the
  day-to-day lives of people
• Internet still very young, and rapidly evolving.

3
Introduction and History (Contd)

• The Origin
• Began as ARPANET in 1969 for the purpose of
  sharing computing resources
• ARPANET was funded by the Department of Defense
• Met with resistance even by university research
  groups who did not wish to be linked to the
  ARPANET
• Used packet switching as opposed to circuit
  switching

4
Introduction and History (Contd)

• Circuit Switching

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Introduction and History (Contd)

• Circuit Switching
• Physical connection established between
  communicating end-points.
• Requires setting up the connection before
  communication
• Guaranteed bandwidth
• Predictable and bounded delay

6
Introduction and History (Contd)

• Packet Switching
• No physical connection established between
  communicating end-points.
• Data is sent in blocks called packets
• Each packet is routed independently

7
Introduction and History (Contd)

• Packet Switching

8
Introduction and History (Contd)

• Packet Switching vs. Circuit Switching
• Packets may arrive out-of-order
• Packets may be dropped, since network does not
  guarantee bandwidth
• Packet switching analogous to how we share road
  space

9
Introduction and History (Contd)

• The origins of packet switching
• The roles of Leonard Kleinrock, Paul Baran and
  Donald Davies
• BBNs proposal to use packet switching for
  ARPANET
• The travails of packet switching

10
Introduction and History (Contd)

• Milestones
• Ethernet
• TCP/IP
• E-mail
• Commercialization of the Internet
• World Wide Web

11
Introduction and History (Contd)

• Internet Organizations
• The Internet Society
• The Internet Architecture Board
• The Internet Engineering Task Force
• The Internet Engineering Steering Group
• ICANN

12
Protocol Layering

• What is a protocol?
• What is protocol layering?
• The analogy to postal service.
• Why use protocol layering?
• Simplicity in design
• Flexibility in accommodating new technologies
• Compatibility of applications to systems

13
Protocol Layering (Contd)

• A common implementation

Application Layer
Application Layer
Transport Layer
Transport Layer
Network Layer
Network Layer
Access Layer
Access Layer
Physical Layer
Physical Layer
14
Switches and Routers

• What is a switch and what is a router?
• The problem with achieving performance
• The need for buffers

15
Switches and Routers (Contd)

• Input queueing and output queueing

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Switches and Routers (Contd)

• Head-of-line blocking with input queueing

17
Switches and Routers (Contd)

• Output queueing and head-of-line blocking

18
Switches and Routers (Contd)

• Commercial switches and routers
• Use both input and output queueing
• Use shared buffer for output queueing
• Use complex buffer organizations and queue
  management strategies

19
Virtual Circuit Switching

• Establishes a virtual circuit
• Routes using a virtual circuit identifier on each
  packet
• Packets with same identifier routed identically
  by a switch
• Facilitates easy management of flows of traffic

20
Virtual Circuit Switching (Contd)

• Asynchronous Transfer Mode (ATM)
• Uses virtual circuits
• Proposed for providing performance guarantees as
  in circuit switching using the packet switching
  technology
• Largely used today in the Internet backbone

21
Routing

• What is routing?
• What is a route table?
• What is a best route?

22
Routing (Contd)

• Link State Routing
• Periodically measure cost to each neighbor
• Distribute measurements to all routers in the
  network
• Each router has complete and current information
  on the topology
• Each router independently computes the best
  path

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Routing (Contd)

• Distance-Vector Routing
• Each router maintains a distance-vector, the cost
  to reach each destination from itself.
• Exchanges distance-vectors with neighbors
• Determines the best path neighbor to reach
  destination

24
Routing (Contd)

• Routing in the Internet
• Distance-vector routing used in the Internet core
  (BGP)
• Link-state routing used within domains (OSPF)
• Border routers use both

25
Flow Control and Congestion Avoidance

• What is flow control?
• What is congestion avoidance?
• Design goals
• responsiveness
• performance
• scalability
• simplicity
• fairness

26
Flow Control and Congestion Avoidance (Contd)

• Flow control strategies
• Open loop flow control
• No feedback
• Pre-arranged self-regulation at the source
• Closed loop flow control
• Self-regulation based on feedback

27
Flow Control and Congestion Avoidance (Contd)

• Open loop flow control
• Traffic descriptors
• Token bucket regulator
• token generation
• bucket capacity

28
Flow Control and Congestion Avoidance (Contd)

• Token bucket regulator

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Flow Control and Congestion Avoidance (Contd)

• Closed loop flow control
• TCP uses closed loop flow control
• slow-start phase in TCP (exponential rate
  increase)
• congestion-avoidance phase in TCP (linear rate
  increase)
• time-outs and back-off

30
Flow Control and Congestion Avoidance (Contd)

• A typical saw-tooth graph of TCP sending rate

31
Flow Control and Congestion Avoidance (Contd)

• Problems with TCP
• Does not avoid congestion, reacts only after
  congestion
• Assumes time-outs are always due to congestion
• Always keeps pushing the network into congestion

32
Flow Control and Congestion Avoidance (Contd)

• Random Early Detection (RED)
• Defines router actions designed to work with TCP
• Goal is congestion avoidance, at good performance
• Detects impending congestion based on queue
  length
• Drops packets before congestion occurs
• Triggers TCP to cut down its rate before it
  causes congestion
• Used in most Internet routers today

33
Emerging Architectures and Services

• Onslaught of multimedia traffic
• Need for service beyond best effort
• What is Quality of Service?
• throughput guarantee
• delay bound
• delay-jitter bound

34
Fairness in Traffic Management

• The most basic guarantee fairness.
• Why not just first-come-first-serve?
• Why not just packet-by-packet round-robin
  scheduling?

35
Fairness in Traffic Management (Contd)

• What is fair and how to be fair?
• All flows with unsatisfied demands should get an
  equal share of the resource
• No flow should be allocated more resources than
  its demand
• Fair queueing is a technique that achieves the
  above two conditions for fairness to a
  satisfactory extent.
• Most Internet routers now implement some version
  of a fair queueing discipline.

36
The Integrated Services Model

• A new architectural framework to facilitate QoS
  in the Internet.
• Applications describe their traffic to the
  network, and their demand for QoS
• Network decides if the demand can be satisfied
  before admitting the application traffic
• Routers reserve bandwidths and buffers necessary
  to satisfy demand

37
The Integrated Services Model (Contd)

• Flow specifications
• TSpec
• burst size
• long-term average rate
• maximum packet size
• peak rate
• RSpec
• service rate
• delay bound
• packet loss probability

38
The Integrated Services Model (Contd)

• Service Classes
• Guaranteed service
• Provides hard guarantees
• Requires per-flow management in the routers
• Suffers from scalability problems
• Controlled Load Service
• Service similar to best-effort in a lightly
  loaded network
• Meant for applications that can tolerate some
  loss or delay
• Requires application to specify traffic
  description
• Network decides whether or not to admit a new
  flow for controlled load service

39
The Integrated Services Model (Contd)

• Signaling (RSVP)
• RSVP is an IP signaling protocol
• Uses two messages Path and Resv
• Path messages go from the sender to the receiver,
  containing traffic description
• Resv messages go from receiver to the sender,
  containing QoS requirements

40
The Integrated Services Model (Contd)

• Flow of Path and Resv messages

41
The Integrated Services Model (Contd)

• Multicasting with RSVP
• RSVP explicitly designed for multicast
• Multicast method based on data replication in the
  network
• Allows merging of Resv requests
• RSVP is a soft-state protocol

42
The Differentiated Services Model

• Differentiated Serevices model is more scalable.
• Traffic is divided into classes
• Resources allocated on a per-class basis instead
  of a per-flow basis
• Defines a set of Per-Hop Behaviors (PHBs)
• Service by the network based on the PHB carried
  in the packet
• Standard PHBs
• Expedited Forwarding
• Assured Forwarding

43
The Differentiated Services Model (Contd)

• Expedited Forwarding (EF-PHB)
• A request to forward the packet as quickly as
  possible
• Meant for applications with stringent delay
  requirements
• Requires strict regulation at source
• Requires careful capacity planning

44
The Differentiated Services Model (Contd)

• Assured Forwarding (AF-PHB)
• Delivers with high assurance (a weaker guarantee)
• Consists of 4 classes and 3 drop precedence
  levels
• In-order delivery within each class
• Drop precedence defined at the source end

45
The Differentiated Services Model (Contd)

• A potential DiffServ scenario

46
Multi-Protocol Label Switching

• Uses the concept similar to that of virtual
  circuits in IP
• Uses fixed-size labels
• Originally designed to facilitate sending IP
  packets over ATM
• Packets are routed based on the label, instead of
  destination address.
• Supported by high-end routers today
• Achieves lower header overhead

47
Multi-Protocol Label Switching (Contd)

• Achieves separation of control and forwarding
  components

48
Multi-Protocol Label Switching (Contd)

• A limitation of traditional routing

49
Multi-Protocol Label Switching (Contd)

• MPLS extends routing functionality

50
Concluding Remarks

• Internet is still evolving, and very rapidly.
• Service requirements of applications may change
  new solutions such as active networking are
  emerging.
• Engineering the Internet continues to be both
  challenging and rewarding.