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