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Chapter 8: Internet Operation
Business Data Communications, 5e
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
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)
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
Subnet Mask Calculations
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
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
Border Grouping Protocol (BGP)
• Preferred ERP for the Internet
• Three functional procedures– Neighbor acquisition– Neighbor reachability– Network reachability
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
Autonomous System Example
Directed Graph of Example
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
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
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
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
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
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
Application Delay Sensitivity
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.
DS Service:Performance Parameters
• Service performance parameters
• Constraints on ingress/egress points
• Traffic profiles
• Disposition of excess traffic
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.
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
DS Configuration Diagram
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
Traffic Conditioning Diagram
Token Bucket Scheme