comm basics 2on1a

8/7/2019 Comm Basics 2on1a

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Communication Systems Basics of communication and Internet 1.1 04/05 www.tm.uka.de

Outline Communication trends and scalability

Basics of data communication

How the Internet works

Design Principles and threats for the Internet architecture

Basics of Communication

and the InternetCircle Lecture Communication Systems

Winter Term 2004/2005

Prof. Dr. M. ZitterbartInstitute of TelematicsDr.-Ing. Roland Bless


Communication Trends

Mobile Communications

Paradigm: anybody, anytime, anywhere

Expected: more mobile phone subscribers than POTS subscribers(Germany: already 48 Mio. at the end of 2000)

Technical Communications Today: communication between users

Tomorrow: communication between machines, e.g.

Production infrastructure: tele-metrics, tele-diagnosis, tele-operations

Communications between vehicles:

Home networks: sensors, security, appliances

IP-based Communications

Internet Protocol IP as media independent access Voice-Over-IP technology is rolling out

All-IP networks: Telcos will switch to IP for voice calls


2/23


Everything goes IP

IP

IP

IP


Internet Growth

#Hosts worldwide (Mio.)

0

50

100

150

200

250

300

91 92 93 94 95 96 97 98 99 00 01 02 03 04

Year

Survey based on #hosts registered in DNS


3/23


Constant change is presumably the only constant in the Internet

Internet survived the tremendous growth: it still works!

One says: it is scalable

What means scalability?

ScalabilityA scalable system works even when there is tremendous growth (e.g., byseveral orders of magnitude, i.e., over several scales) of certain systemparameters

Why important? Technological development shows often leaps in order of amagnitude (c.f. Moores Law, CPU, bandwidth, memory)

Example for no or bad scalability:

Performance of a non-scalable system decreases (strongly) as certainparameter values increase, possibly until the whole system fails

Growth and Scalability

t

X(t)

X(t)

Systemperformance


Evolving Internet important aspects

Past

Data communication between research institutions

Common goals

Trust relationships between users

Technically skilled users

Consistent and coherent architecturePresence

Global infrastructure of the information society

New interest groups and commercialization (ISPs, service providers)

Loss of trust relationships

Average consumers, technically unskilled

Out of own interests, technologies and extensions are realized, which

are used for short-time fulfillment of demand

are largely done without architectural thinking

are not consistent with the Internet architecture

endanger the coherence of the internet


4/23


Data Communications

Communication (original meaning):

Exchange of data between human communication partners.

Every concrete communication is data communication

N.B.: Information is extracted from data by the process of interpretation

Data communication(more narrow definition in literature and habitual language use):

Transmission of digital data between telecommunication devices

Communication (Usage of the term in this lecture):

immaterial media:

Energy flows, usually electric currents, electromagnetic waves

Opposite: material data transport (e.g. letters, shipping of disks)

Data (tele)communication is the generic term for each dataexchange using immaterial media and greater distances

between men and/or machines(abbreviated: Data communication = communication).

Data (tele)communication is the generic term for each dataexchange using immaterial media and greater distancesbetween men and/or machines

(abbreviated: Data communication = communication).


Basic model of telecommunication

Participants act as senders or receivers

The service usage by participants occurs at a special service interface, using

a service access point Different service primitive types: Request, Indication, Response, Confirmation

The Medium bridges the spatial distance

medium

sender receiver

messagemessage

spatial distance

service interfaceservice

access point


5/23


What is a protocol?A communication protocol describes a set of rules, according to which thecommunication between two or more parties must be performed.

TCP/IP protocols

e.g. file transfer, electronic mail

Computer communication protocols

Communication protocols

e.g. discussion, conversation

Ethernet WLAN

IPX DECnet

ISO/OSI protocols

AppleTalk


Service and Protocol

Service User 1 Service User 2

ServiceProvider 1

ServiceProvider 2

Service

Service

Protocol


6/23


A Model for Telecommunication Systems

Sender Receiver

Physical medium

telecommunication system

...

...

layer n

layer n-1

layer 1entity 1entity 1

entity n-1entity n-1

entity nentity n

entity 1entity 1

entity n-1entity n-1

entity nentity n

A layer offers a service to its upper layer

The service is provided by the cooperation of the layer entitiesaccording to a specified protocol


ISO/OSI and Internet Model

ISO/OSI too complex, but OK as logical model

Too restrictive (no cross-layer information exchange)

Redundant functionality in different layers

Too heavy-weight for simple network devices like printers, etc.

Internet model similar, but simplified (esp. Application layer)

Media Access

Internet

Transport

Application

Physical

Data Link

Network

Transport

Session

Application

Presentation

ISO/OSI BasicReference Model

InternetReference Model

7

6

5

4

3

2

1


7/23


Physical Layer

Tasks

Accesses the physical medium directly (e.g. cable)

Unsecured connection between systems

Transport of unstructured bit sequences via a physical medium

Comprises (among other things) physical link, conversion data signals

Signal Transmission Modes

Baseband Transmission

Native and fully digital:discrete signal levels, periodic and discrete transition intervals

Maximum data rate for channel with bandwidth B according to

Nyquist: rmax [bit/s] =2 B log2 n, (n=number of discrete levels, noise-less channel)

Shannon: rmax [bit/s] = B log2 (1 + S/N) (noisy channel, S/N=Signal-to-noise ratio)

Broadband Transmission

Modulation (amplitude, frequency, phase or combination thereof)

Modem (modulator/demodulator) required

t

S(t)

t

S(t)


Medium-Access/Data Link Layer

Tasks

Structuring the data stream

Synchronization, Framing, Code Transparency

Protection against errors and loss

Use of checksum to detect bit errors (e.g., CRC: Cyclic Redundancy Check)

Reliable link layers use sequence numbers, timers and acknowledgments todetect loss of data packets and to recover by automatic retransmission

Flow control

Media access control in case of shared media

Network Access

Local Area Networks, e.g., Ethernet, Token-Ring, Token-Bus, WirelessLANs, ....

Ethernet-Frame

Metropolitan Area and Wide-Area Networks: Modems, Fiber, DSL, ...

Preambel56 bit

Preambel

56 bit StartDel(8 bit)

StartDel

(8 bit) DestAddr(16/48 bit)

DestAddr

(16/48 bit) SrcAddr(16/48 bit)

SrcAddr

(16/48 bit) Length(16 bit)

Length

(16 bit) Data(12.000 bit)

Data

(12.000 bit) PAD(0-368 bit)

PAD

(0-368 bit) FCS(32 bit)

FCS

(32 bit)


8/23


Network Layer

Tasks

Concatenation of point-to-pointconnections to end-system connections

Uniform addressing of nodes

Address mapping todata link layer addresses

Transmission quality possiblyselectable

Routing

Flow control, congestion control

Switching concepts

Circuit Switching (Classical telephony, e.g. ISDN)

Packet Switching (Internet)

Virtual Connections (ATM: Asynchronous Transfer Mode)

Message Relaying

Physical Medium

Media Access

NetworkLayer

TransportLayer

Application-orientedLayers

End-system A End-system B

IEEE 802.3IEEE 802.3

IPIPIP

TCPTCPTCP

IEEE 802.3IEEE 802.3

IPIPIP

IEEE 802.5IEEE 802.5 IEEE 802.5IEEE 802.5

IPIPIP

TCPTCPTCPIntermediate System

Physical Medium


Network Layer: Internet Protocol

E-Mail, WWW, Telephony ....

SMTP, HTTP, RTP, BEEP, ...

UDP, TCP,

SCTP, ...

IP

Ethernet,PPP, ...

CSMA, CDMA, Asynch., SDH, ...

Copper, Glass Fibre, Radio, ...

IP layer enables

Bigger network

Global addressing

Hide network details and changesfrom end-to-end protocols

A single protocol (Hourglass Model)

maximizes interoperability

minimizes the number of service interfaces

Lean protocol

Requires minimal common network functionality

in order to maximize the numberof usable networks

End-to-End principle

Robustness by stateless operation

See also:

http://www.iab.org/Documents/hourglass-london-ietf.pdf


9/23


Routing in the Internet

Problem

How are data packets forwarded in the Internet?

Method

Routing table gives information about the next hop

The protocol IP(Internet Protocol) conducts theforwarding of data

Datagram protocol

connectionless

unreliable

segmentation andreassembly

Uses Internet addressing Uses further protocols like

ICMP (Internet Control Message Protocol)

ARP (Address Resolution Protocol)

IGMP (Internet Group Management Protocol)

Transport layer: UDP, TCP

Data link layer

Physical layer

Routing protocols RIP, OSPF, BGP

Routing protocols RIP, OSPF, BGP

Protocol IP Addressing Datagram formatPacket handling

Protocol IP Addressing Datagram formatPacket handling

Protocol ICMP error reports Signalling betweenrouters

Protocol ICMP error reports Signalling betweenrouters

Routingtable

Address resolution ARP, RARP

Address resolution ARP, RARP


Format of an IPv4 data unit

Type of Service (8)

Total Length (16)

Identifier (16)

Time to Live (8)

Protocol (8)

Header Checksum (16)

Source Address (32)

Destination Address (32)

Options and Padding (variable)

Data (variable)

Header Length (4)Version (4)

Flags (3) Fragment Offset (13)

P P P D T R 0 0

reservedPrecedence111 Network Control110 Internetwork Control

101 CRITIC/ECP100 Flash Override011 Flash010 Immediate001 Priority000 Routine

According toRFC 791(obsolete)

Delay: 0 normal1 low

Throughput: 0 normal1 high

Reliability: 0 normal1 highNEW:

0 1 2 3 4 5 6 7

R

6 7543210

DS FieldDifferentiated Services

ECNExplicitCongestionNotification


10/23


Structure of IPv4 addresses

Subnet masks mark the area of the IP address describing the network and the sub-network. This area is marked as ones (1) in the binary form of the subnet mask.

Example

IP address: 129. 13. 3. 64

Subnet mask: 255. 255. 255. 0 =1111 1111 1111 1111 1111 1111 0000 0000

Network written in prefix notation: 129.13.3.0/24

Globally visible network is only 129.13.0.0/16 (formerly Class B network)

Network: 129. 13.

Subnet: 3.

End system: 64

If the subnet mask only covers the network part, there is no subnet part(e.g. subnet mask 255.255.0.0 in case of class B)

Note: Systems attached to several networks (e.g. routers), have several, network-specificIP addresses!

IP addresses

network partnetwork part

network partnetwork part subnet partsubnet part end systemend system

local partlocal part


Mapping of IP and MAC addresses If (Destination IP address AND Subnet mask)

= (Own IP address AND Subnet mask) Receiver is in the same IP subnet! So I can use a link layer connection...

Problem:Which MAC address does the next system on the route to the target have?

Scheme

Application

08002B90102456

Application

????????????????

TCP

IP

MAC

TCP

IP

MAC

12 . 0 . 0 . 34

TCPConnect with

12 . 0 . 0 . 21

12 . 0 . 0 . 21

Internet


11/23


Forwarding in an IP router

Routing table (Routing Information Base) Constructed by routing protocols: contains several alternative routes to the destination

Forwarding table (Forwarding Information Base) Only selected/active routes: IP address of next hop and identification of the interface used

Address resolution table Built by ARP: MAC address of the next system for the IP address of the end system

Example Destination: end system B; Source: end system A

Data packet on the way from router 1 to router 2:

MAC addresses: MAC address IP-Router 2 (dest) and MAC address IP-Router 1(source)

IP addresses: end system B (destination), end system A (source)

End system A

129.13.3.108

End system B

145.5.9.27

MAC-BMAC-A

IP-Router 1

IP-Router 2

129.13.3.60

132.2.2.3

132.2.2.7

145.5.9.19


Forwarding in an IP router

Router functions

Determine the IP address of the subsequent system (Next Hop)

Simple routers have often only a routing table for their subnets and a default route for allother destinations

Mapping of this IP address to the connection point address (MAC address)

Sending the IP data unit to the next hop on the corresponding interface via layer 2

IP addresses (Source/Destination) in the IP packet remain unchanged!

Router 1

129.13.3.108145.5.9.27

MAC-AMAC-B

Router 2

129.13.3.60132.2.2.3

132.2.2.7145.5.9.19

MAC-R2-A

MAC-R1-B

...145.5.9.27

129.13.3.108

145.5.9.27

...

Network scenario with router

IP addresses MAC addresses

End system AEnd system B

If A If B If A If B


12/23


Network layer protocols

IP (Internet Protocol)

ARP (Address Resolution Protocol)

RARP (Reverse ARP)

ICMP (Internet Control Message Protocol)

IGMP (Internet Group ManagementProtocol)

SNAP (Subnetwork Access Protocol)

Routing protocols

RIP (Routing Information Protocol)

BGP (Border Gateway Protocol)

EGP (External Gateway Protocol)

OSPF (Open Shortest Path First)

Network management

SNMP (Systems Network ManagementProtocol)

Transport protocols:

UDP (Universal Datagram Protocol)

TCP (Transmission Control Protocol)

ARP RARP

ICMP IGMP

SNAP

LLC-1

Internet Protokoll

BGP RIP SNMP

EGP /IGP

OSPFTCP UDP

Routing in the Internet

Protocols in an IP router


Splitting networks into Autonomous Systems (AS) Otherwise entries in routing tables and amount of exchanged routing

information not scalable

Routers within AS have usually only detailed routing information about own AS

There is at least one designated router that acts as interface to other ASes

Advantages

Scalability Internal routing table size depends on size of AS

Changes within AS are usually only propagated within the AS if external connectivity is notaffected

Autonomy Internet = Network of networks

Routing is controlled by own organization

Unique routing strategy within own system

Internal routing protocols can vary between ASes

Routing Hierarchy: View from 10,000m

AS 110

AS 111AS 100

AS 101 AS 113

AS 112

AS 114

AS 120

AS 121

AS 122


13/23


14/23


Why Intra- and Inter-AS routing protocols?

Policy

Political question: which transit traffic is allowed to traverse the AS?

Inter-AS: policies are selected by the provider

Intra-AS: one organization, few policies necessary

Scalability

Inter-AS: further abstraction level;Size of routing tables and number of updates can be reduced, as failures withinone AS can mostly remain hidden

Intra-AS: higher stability

Performance

Inter-AS: Policies are necessary and more important than performance metrics Intra-AS: Concentration on performance metrics


Vertex=Node(router/

subnet)

Intra-AS Routing

Well-known protocols for Intra-AS routing are

RIP (Routing Information Protocol) Distance Vector Protocol

OSPF (Open Shortest Path First) Link State Protocol

IS-IS (Intra-Domain Intermediate System to Intermediate System RoutingProtocol) Link State Protocol

originally ISO/OSI routing protocol

used for IP by big providers

EIGRP (Enhanced Interior Gateway Routing Protocol)

CISCO proprietary

Intra-AS routing protocols are often called Interior Gateway Protocols (IGP)

OSPF:

Connectivity and link states are flooded through the network

Every router has the same view of the network

Network is mapped to Graph (V,E) Calculates shortest paths

with Dijkstras algorithmEdge=Link


15/23


OSPF hierarchy in an Autonomous System

virtual

connection

interior Router

border router

N: Network

R: Router

ABR: Area Border Router

ASBR: AS Boundary Router

BBR: Backbone Router

Routing Area(OSPF Area)

R4(ABR)

R3

(ABR)

R2

R1

R6

R13(ASBR)

R12(BBR)

ASBR/ABR

R8

ASBR/ABR

R5

Autonomous System

N1

N2

N3

N4

R9

R11

R10

R7(ABR)

ASBR/ABR


Inter-AS Routing: Exterior BGP (EBGP)

Exterior BGP is used between the BGP routers (also called BGPspeakers) connecting two ASes

Path Vector protocol (AS path)

Learn all destination prefixes that can be reached through the other AS

An AS can prevent to receive traffic for certain destination by not

announcing any route to it (i.e., policy by route filtering) These BGP routers should be directly connected

Internal information will NEVER be forwarded directly to other BGPspeakers

AS 1 AS 2

BGP Speaker


16/23


Example for BGP topology

110.0.0.0/8

111.0.0.0/8

100.0.0.0/8

101.0.0.0/8 113.0.0.0/8

112.0.0.0/8

114.0.0.0/8

120.0.0.0/8

121.0.0.0/8

122.0.0.0/8

I want to send data to AS122!Which route should I use?

Routing table AS100Network Next Hop Metric LocPrf Weight Path*> 121.0.0.0 10.1.1.110 0 110 114 121 i*> 122.0.0.0 10.1.1.110 0 110 114 122 iRouting table AS110

Network Next Hop Metric LocPrf Weight Path* 121.0.0.0 10.1.1.111 0 111 112 114 121 i* 10.1.1.113 0 113 114 121 i*> 10.1.1.114 0 114 121 i*> 122.0.0.0 10.1.1.114 0 114 122 i* 10.1.1.111 0 111 112 114 122 i* 10.1.1.113 0 113 114 122 i

AS 100

AS 101

AS 110AS 113

AS 111

AS 112

AS 114

AS 122

AS 121

AS 120

Routing table AS114Network Next Hop Metric LocPrf Weight Path*> 112.0.0.0 10.1.1.112 0 0 112 i* 10.1.1.110 0 110 111 112 i*> 122.0.0.0 10.1.1.122 0 0 122 i


Routing in "Default-Free-Zones"

Two modes of operation of BGP (same protocol,but different rules) for the distributionof routing information

Between two AS: with EBGP (External BGP)

Within one AS: with IBGP (Internal BGP)

Internal full mesh ofTCP connections necessary

No distribution of routes learnt withIBGP to IBGP neighbors

AS X

IBGP

EBGP

EBGP

IBGP

EBGP

AS Y

EBGP

IBGP

Full mesh unsuitable for big AS,

possible solution lies in the implementation ofRoute reflectors (dedicated routers aspeering points)Confederations (private sub-AS)

EBGP

EBGP


17/23


Interior BGP (IBGP)

BGP routers within one AS are connected with IBGP

IBGP routers have to be fully meshed

To learn routes for all external prefixes

They inform about new networks (e.g. LANs)

They do not propagate internal prefixes outwards

No direct physical connections (but logical connections) between routersnecessary

Each IBGP router must be able to communicate with each other IBGProuter

IBGP messages are never forwarded to other BGP routers (to preventloops)


Transport Layer

Tasks

End-to-end service

application-based addressing (Ports)

reliable/unreliable

Reliable protocol

Error and loss detection Retransmission

Segmentation/Reassembly

Flow control

Congestion control

Examples

TCP (Transmission Control Protocol)

UDP (User Datagram Protocol) SCTP (Stream Control Transmission Protocol)

DCCP (Datagram Congestion Control Protocol)


18/23


Application Layer

Protocols depend on the particular application

This is also end-to-end

Examples of protocols above the transport layer:

telnet (Remote Login)

SSH (Secure Shell, secure replacement for telnet)

FTP (File Transfer Protocol)

HTTP (Hypertext Transfer Protocol, HTML/Web Content Transport,Server/Client)

BEEP (Blocks Extensible Exchange Protocol, Peer-to-Peer, many features)

SSL/TLS (Transport Layer Security)

SMTP (Mail Transport)

DNS (Domain Name System) RTP (Streaming)

Routing Protocols (OSPF, BGP, ...)

...many more...


Internet architecture: Design goals

Paper by D. Clark The Design Philosophy of the DARPA Internet Protocols

(SIGCOMM '88) names:

Fundamental goal: Internetworking (Connection of existing networks)

Further goals (ordered by their importance):

Robustness: sustain internet communication despite failure of networks and

routers Support of multiple types of communication services

Heterogeneity: Accommodation of a variety of networks

Distributed resource management

Cost effectiveness

Host attachment with a low level of effort

Resources used must be accountable

Robustness against failures

Fate-Sharing: acceptable to loose the state information associated with an

entity if, at the same time, the entity itself is lost

Do not store state in the network, but in the end systems instead

Datagram concept as a consequence


19/23


Design principles: End-to-End Argument

Decisions necessary in system design

Which functionality is needed?

Where should certain functions be placed?

In the end systems or applications?

In the network?

Important design principle

(explicitly expressed as recently as 1981 by Saltzer, Reed and Clark)

The End-to-End-Argument (E2E argument):The function in question can completely and correctly be

implemented only with the knowledge and help of the application standingat the end points of the communication system. Therefore, providing thatquestioned function as a feature of the communication system itself is not

possible. (Sometimes an incomplete version of the function provided by thecommunication system may be useful as a performance enhancement.)


Discussion End-to-End-Argument

This means especially:specific functionality of the application layer usually can and shouldpreferably not be placed in the network itself

Minimality principle:

Avoid integrating more than the essential and necessary functionality into thenetwork

Keep unnecessary functionality out of the network Keep it simple

Not a strict law, rather a guideline

Further goals and consequences of the E2E argument:

Protection of innovation

Simple to add new services

Hard to change the infrastructure (see introduction of Multicast, IPv6, ECN, etc.)

Reliability and robustness against failure and malfunction of end systems and network components

If network components have to store state, the probability of connection failuresgrows with increasing network size


20/23


Consequences End-to-End-Argument

Examples:

Reliable file transfer

Possible sources of error:

Read errors in the end system

Software errors during copying or buffering of data by the file system or file

transfer program

Hardware errors during these processes in CPU, memory, bus, etc.

Loss, bit errors or duplicates in the communication system

Crash/Failure of end systems (sender or receiver) during or after transfer

Reliability of the communication system does not eliminate all errors

Division of TCP/IP into TCP and IP in the late 70s

End-to-End security Suppression of duplicates (e.g. caused by the application itself)


Internet Architecture: Principles

RFC 1958: Architectural Principles of the Internet

Independence of the Internet Protocol of the medium and of hardware

addressing

If states have to be stored (e.g. routes, QoS-guarantees, Header

Compression, ...), they should be self-healing

Adaptive procedures and protocols for deriving and maintaining states

Soft-State concept: State is periodically renewed (refreshed)

Reduction of state information to a minimum

Manually configured states should be reduced to an absolute minimum


21/23


Further design aspects

RFC 3426 General Architectural and Policy Considerations(Internet Architecture Board)

basic issues concerning protocol and system design

no guidelines, no checklist

Discussion and explanation on the basis of numerouscase studies (e.g. ECN)

RFC 1122 Requirements for Internet Hosts -- Communication Layers

Good documentation and discussion of design decisions

Robustness principle (Jon Postel, see also http://www.postel.org):

Be liberal in what you accept, and conservative in what you send

Software should be able to react appropriately to every error even if itis highly unlikely

Incoming packet can contain any combination of faults and attributes

Assumption of intended/malicious generation of such packets


Many aspects have changed since the outset of the internet

Threats to the End-to-End-Argument? [RFC 3724]

Loss of trust between end systems Introduction of security technologies

Middleboxes (Proxies/NATs/Firewalls/Caches/...)

Break of the End-to-End Principle (esp. security mechanisms) New service models: Quality of service becomes part of the service

(Streaming A/V) Servers are distributed and placed closer to the user(e.g. Akamai, Realnetworks...)

New parties involved: Internet Service Provider, Administrators of companynetworks, governments Restriction of services, interest of interposing (e.g. as a Trusted ThirdParty or for eavesdropping/taxation/censorship...)

Technically uninterested users Context and configuration information is placed in the network in order todisburden the user

Trends opposed to the E2E principle (1)

Middlebox


22/23


Trends opposed to the E2E principle (2)

Example: negative effects by security technologies

Elimination of PATH-MTU-Discovery mechanisms by rigorous filteringof ICMP packets

Filtering of packets with their ToS-Bits set prevents the usage of Explicit

Congestion Notification Limitation of accessibility and available services by private addressing

in Intranets

Possible procedure for future mechanisms which seem to infringe upon theEnd-to-End principle:Split E2E-Argument into the components

Protection of innovation

Introduction of new mechanisms is easier in end systems

Reliability/Robustness and trust

add security, where necessary


Loss of internet transparency

Internet Transparency [RFC 2775]:

original concept of a single universal logical addressing scheme

Mechanisms which allow packets to flow essentially unchanged fromsource to destination

Loss of transparency by:

Intranets (Security, Restriction of applications and address transparency,network administrator has control) Dynamic addresses (SLIP/PPP, DHCP) Firewalls (Restriction of services and accessibility) SOCKS/Application Level Gateways Private addresses (not unique, restriction of accessibility and global

communication) Network Address Translators (NATs) Application Level Gateways, Proxies, Caches Voluntary isolation (e.g. WAP-Proxies) and partner networks Split-DNS Tricks for load balancing


23/23


Conclusions

Today we have networks everywhere, and, they are a critical part of the ITinfrastructure

Most network systems and architectures use Internet protocols

The Internet is a very scalable system

Accommodated the tremendous growth in the past

Thanks to the wise design decisions and architectural principles

But for how long will its success continue?

Requirements for more connectivity, machine-to-machine communicationetc. lead to the use of IPv6

Current Inter-Domain routing scheme will probably fail to cope with growthof the next two decades...

Tussle and conflicts in the Internet caused by parties with different interests