Chapter 8: Internet Operation

1
Chapter 8 Internet Operation

• Business Data Communications, 5e

2
Network Classes

• Class A Few networks, each with many hostsAll
  addresses begin with binary 0
• Class B Medium networks, medium hostsAll
  addresses begin with binary 10
• Class C Many networks, each with few hosts All
  addresses begin with binary 11

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Internet Addressing

• 32-bit global internet address
• Includes network and host identifiers
• Dotted decimal notation
• 11000000 11100100 00010001 00111001 (binary)
• 192.228.17.57 (decimal)

4
Subnets Subnet Masks

• Allows for subdivision of internets within an
  organization
• Each LAN can have a subnet number, allowing
  routing among networks
• Host portion is partitioned into subnet and host
  numbers

5
Subnet Mask Calculations
6
Internet Routing Protocols

• Responsible for receiving and forwarding packets
  between interconnected networks
• Must dynamically adapt to changing network
  conditions
• Two key concepts
• Routing information
• Routing algorithm

7
Autonomous Systems

• Key characteristics
• Set of routers and networks managed by single
  organization
• group of routers exchanging information via a
  common routing protocol
• connected (in a graph-theoretic sense) that is,
  there is a path between any pair of nodes
• Interior Router Protocol (IRP) passes information
  between routers in an AP
• Exterior Router Protocol (ERP) passes information
  between routers in different Aps

8
Border Grouping Protocol (BGP)

• Preferred ERP for the Internet
• Three functional procedures
• Neighbor acquisition
• Neighbor reachability
• Network reachability

9
Open Shortest Path First (OSPF)

• Widely used as IRP in TCP/IP networks
• Uses link state routing algorithm
• Routers maintain topology database of AS
• Vertices
• Router
• Network
• Transit
• Stub
• Edges
• Connecting router vertices
• Connecting router vertex to network vertex

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Autonomous System Example
11
Directed Graph of Example
12
The Need for Speed andQuality of Service (QoS)

• Image-based services on the Internet (i.e., the
  Web) have led to increases in users and traffic
  volume
• Resulting need for increased speed
• Lack of increased speed reduced demand
• QoS provides for varying application needs in
  Internet transmission

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Emergence of High-Speed LANs

• Until recently, internal LANs were used primarily
  for basic office services
• Two trends in the 1990s changed this
• Increased power of personal computers
• MIS recognition of LAN value for client/server
  and intranet computing
• Effect has been to increase volume of traffic
  over LANs
• Result exceeds capacity of standard 10mbps and
  16mbps networks

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Corporate WAN Neds

• Greater dispersal of employee base
• Changing application structures
• Increased client/server and intranet
• Wide deployment of GUIs
• Dependence on Internet access
• More data must be transported off premises and
  into the wide area

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Digital Electronics

• Major contributors to increased image and video
  traffic
• DVD (Digital Versatile Disk)
• Increased storage means more information to
  transmit
• Digital cameras
• Camcorders
• Still Image Cameras

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Categories of Traffic

• Elastic
• Can adjust to changes in delay and throughput
  access
• Examples File transfer, e-mail, web access
• Inelastic
• Does not adapt well, if at all, to changes
• Examples Real-time voice, audio and video

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Requirements of Inelastic Traffic

• Throughput
• Minimum value may be required
• Delay
• Services like market quotes are delay-sensitive
• Delay variation
• Real-time applications, like teleconferencing,
  have upper bounds on delay variation
• Packet loss
• Applictions vary in the amount of packet loss
  allowable

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Application Delay Sensitivity
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Differentiated Services

• Provide QoS on the basis of user needs rather
  than data flows
• IP packets labeled for differing QoS treatment
• Service level agreement (SLA) established between
  the provider (internet domain) and the customer
  prior to the use of DS.
• Provides a built-in aggregation mechanism.
• Implemented in routers by queuing and forwarding
  packets based on the DS octet.
• Routers do not have to save state information on
  packet flows.

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DS ServicePerformance Parameters

• Service performance parameters
• Constraints on ingress/egress points
• Traffic profiles
• Disposition of excess traffic

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DS Services Provided

• Traffic offered at service level A will be
  delivered with low latency.
• Traffic offered at service level B will be
  delivered with low loss.
• 90 of in-profile traffic delivered at service
  level C will experience no more than 50 ms
  latency.
• 95 of in-profile traffic delivered at service
  level D will be delivered.
• Traffic offered at service level E will be
  allotted twice the bandwidth of traffic delivered
  at service level F
• Traffic with drop precedence X has a higher
  probability of delivery than traffic with drop
  precedence Y.

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DS Field

• Packets labeled for handling in 6-bit DS field in
  the IPv4 header, or the IPv6 header
• Value of field is codepoint
• 6-bits allows 64 codepoints in 3 pools
• Form xxxxx0 - reserved for assignment as
  standards.
• Form xxxx11 - reserved for experimental or local
  use.
• Form xxxx01 - also reserved for experimental or
  local use, but may be allocated for future
  standards action as needed.
• Precedence subfield indicates urgency
• Route selection, Network service, Queuing
  discipline
• RFC 1812 provides two categories of
  recommendations for queuing discipline
• Queue Service
• Congestion Control

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DS Configuration Diagram
24
DS Configuration Operation

• Routers are boundary or interior nodes
• Forwarding treatment is per-hop behavior (PHB)
• Boundary nodes handle traffic conditioning
• Classifier
• Meter
• Marker
• Shaper
• Dropper

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Traffic Conditioning Diagram
26
Token Bucket Scheme