Chapter 8: Internet Operation

Chapter 8: Internet Operation

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

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

Subnetworking Example

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 AS (Autonomous systems)

• Exterior Router Protocol (ERP) passes information between routers in different AS

Border Gateway Protocol (BGP)

• Preferred ERP for the Internet

• BGP-4 is the current version

• 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

Open Shortest Path First (OSPF) Protocol

• Widely used interior protocol to TCP/IP networks

• Computes a route through the network that incurs the least cost

• User can configure the cost as a function of:-delay-data rate-cost

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

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

QoS on the Internet

• Elastic Traffic– Can adjust to changes in delay and throughput

access– Examples: File transfer, e-mail, web access

• Inelastic Traffic– 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

Service Level Agreements (SLA)

• Contract between the network providor and customer that defines sepecific aspects of the service provided.

• Typically includes:-Service description-Expected performance level-Monitoring and reporting process

SLA ExampleMCI Internet Dedicated Service

• 100% availability

• Average round trip transmissions of ≤ 45 ms with the U.S.

• Successful packet delivery rate ≥ 99.5%

• Denial of Service response within 15 minutes

• Jitter performance will not exceed 1 ms between access routers

IP Performance Metrics

• Three Stages of Metric Definitions-Singleton-Sample-Statistical

• Active techniques require injecting packets into the network

• Passive techniques observe and extract metrics