1.internet fundamentals nr

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INTERNET FUNDAMENTALS

Nauru12 August 2019

22

Agenda• Internet Operations

• Internet Protocols and Operations• Internet Resource Management

• IP Addressing

• DNS & Reverse DNS

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INTERNET OPERATIONS FUNDAMENTALS

44

In the beginning…• 1968 - DARPA

– (Defense Advanced Research Projects Agency) contracts with BBN to create ARPAnet

• 1969 – First four nodes

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The Internet is born… • 1970 - Five nodes:

– UCLA – Stanford - UC Santa Barbara - U of Utah – BBN

• 1971 – 15 nodes, 23 hosts connected

• 1974 – TCP specification by Vint Cerf & Bob Kahn• 1983 – TCP/IP

– On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging

6

Pre 1992

RFC 10201987

RFC 12611991

“The assignment of numbers is also handled by Jon. If you are developing a protocol or application that will require the use of a link, socket, port, protocol, or network number please contact Jon to receive a number assignment.”

RFC 7901981

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Address Architecture - History• Initially, only 256 networks in the Internet!

• Then, network “classes” introduced:– Class A (128 networks x 16M hosts)– Class B (16,384 x 65K hosts)– Class C (2M x 254 hosts)

8

Address Architecture - Classful

A (7 bits) Host address (24 bits)

Class A: 128 networks x 16M hosts (50% of all address space)

0

B (14 bits) Host (16 bits)10

Class B: 16K networks x 64K hosts (25%)

C (21 bits) Host (8 bits)110

Class C: 2M networks x 254 hosts (12.5%)

0-127

128-191

192-223

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Internet Challenges 1992 • Address space depletion

– IPv4 address space is finite– Historically, many wasteful allocations

• Routing chaos– Legacy routing structure, router overload– CIDR & aggregation are now vital

• Inequitable management– Unstructured and wasteful address space distribution

10

• Network boundaries may occur at any bit

Classless & Classful addressing

16K networks x 64K hosts

128 networks x 16M hostsA

B2M networks x 256 hosts

C

Obsolete• inefficient• depletion of B space• too many routes from C space

Classful ClasslessBest Current

Practice

Addresses Prefix Classful Net Mask... ... ... ...8 /29 255.255.255.248

16 /28 255.255.255.24032 /27 255.255.255.22464 /26 255.255.255.192

128 /25 255.255.255.128256 /24 1 C 255.255.255.0... ... ... ...4096 /20 16 C’s 255.255.240.08192 /19 32 C’s 255.255.224

163843276865536

/18/17/16

64 C’s128 C’s

1 B

255.255.192255.255.128255.255.0.0

... ... ... ... *

Classful addressing

is dead!

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1111

Evolution of Internet Resource Management• 1993: Development of “CIDR”

– addressed both technical problems

RFC1519

RFC1518

RFC1517

Address depletionà Through more accurate

assignment• variable-length network

address

Routing table overloadà Through address space

aggregation• “ supernetting”

1212

Evolution of Internet Resource Management• Administrative problems remained

– Increasing complexity of CIDR-based allocations– Increasing awareness of conservation and aggregation – Need for fairness and consistency

• RFC 1366 (1992)– Described the “growth of the Internet and its increasing globalization”– Additional complexity of address management– Set out the basis for a regionally distributed Internet registry system

RFC1366

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1313

Evolution of Address Policy• Establishment of RIRs

– Regional open processes– Cooperative policy development– Industry self-regulatory model

• bottom up

AFRINIC APNIC ARIN LACNIC

AFRINICcommunity

APNICcommunity

ARINcommunity

LACNIC community

RIPENCC

RIPENCCcommunity

1414

How does the Internet work• Physical connectivity and reachability

– Packet switching

• Protocols – common communication and rules– TCP/IP

• Addressing – global accessibility– IPv4, AS numbers, IPv6

• IANA - RIRs

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Internet Routing

The Internet

Net

Net

Net

NetNet

NetNet

Net

Net

Net

Net

Global Routing Table

4.128/960.100/1660.100.0/20135.22/16…

15

1616

Internet Routing

The Internet

Traffic202.12.29.0/24

Announce202.12.29.0/24


4.128/960.100/1660.100.0/20135.22/16…


4.128/960.100/1660.100.0/20135.22/16

202.12.29.0/24…

202.12.29.0/24

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1717

Internet Routing

Local Routing Table

202.12.29.0/25202.12.29.128/25

Traffic202.12.29.142

202.12.29.0/24

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IP Addresses vs Domain Names

The Internet

2001:0C00:8888::My Computer www.apnic.net2001:0400::

www.apnic.net202.112.0.462001:0400::

DNS

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1919

Who Runs the Internet?• No one

• (Not ICANN, not the RIRs, not the governments…)• It is decentralized

2020

How does it keep on working?• Inter-provider business relationships and the need for

customer reachability ensures that the Internet by and large functions for the common good

• Driven by commerce – free market

• Engineers and the Internet community talk to each other

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21

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INTERNET PROTOCOLS AND OPERATIONS

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2323

What is a Protocol?• Set of rules that define the communications process

• defines the structure or pattern for the data transferred – functions or processes that need to be carried out in order to

implement the data exchange– information required by processes in order for them to accomplish

this

• All data is transmitted in the same way irrespective of what the data refers to, whether it is clear or encrypted.

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The OSI Model

Access to the network

Manipulate data (Translate, encrypt)

Manage sessions (connections)

Provide reliable delivery

Internetwork - move packets fromsource to destinationConfigure data for direct delivery by physical layer

Physical delivery - electrical specs etc

Application

Presentation

Session

Transport

Network

Data Link

Physical

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OSI and TCP/IP Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Transport

Internet

Network Access

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Transport

Data Link

Physical

Network

Upper Layer Data

Upper Layer DataTCP Header

DataIP Header

0101110101001000010

DataMAC Header

Presentation

Application

Session

Segment

Packet

Bits

Frame

PDU

FCS

Source: www.cisco.com (ICND v1.0a—1-11)

Encapsulating Data

http://www.cisco.com/

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Upper Layer Data

IP + TCP + Upper Layer Data

MAC Header

TCP+ Upper Layer DataIP Header

Upper Layer Data

TCP Header

0101110101001000010

Transport

Data Link

Physical

Network

PresentationApplication

Session

Source: www.cisco.com (ICND v1.0a—1-11)

De-encapsulating Data

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Internet Protocol (IP)• IP is an unreliable, connectionless delivery protocol

– A best-effort delivery service– No error checking or tracking (no guarantees – Post Office)– Every packet treated independently– IP leaves higher level protocols to provide reliability services (if

needed)

• IP provides three important definitions:– basic unit of data transfer– routing function– rules about delivery

http://www.cisco.com/

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TCP/IP Protocol Structure

ICMP

UDP

SMTP FTP Telnet

IGMP

ARP RARP

DATA LINK

PHYSICAL

DNS ……… HTTP

TCP

IP

From Forouzan

3030

What does a router do?• ?

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A day in a life of a router• find path

• forward packet, forward packet, forward packet, forward packet...

• find alternate path

• forward packet, forward packet, forward packet, forward packet…

• repeat until powered off

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Routing versus Forwarding

Routing = building maps and giving directions

Forwarding = moving packets between interfaces according to the “directions”

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IP Routing – finding the path• Path derived from information received from a routing

protocol

• Several alternative paths may exist– best path stored in forwarding table

• Decisions are updated periodically or as topology changes (event driven)

• Decisions are based on:– topology, policies and metrics (hop count, filtering, delay, bandwidth,

etc.)

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Metric field• To determine which path to use if there are multiple paths to

the remote network

• Provide the value to select the best path

• But take note of the administrative distance selection process J

Routing Protocol MetricRIPv2 Hop countEIGRP Bandwidth, delay, load, reliability,

MTUOSPF Cost (the higher the bandwidth

indicates a lower cost)IS-IS Cost

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IP route lookup• Based on destination IP address

• “longest match” routing– More specific prefix preferred over less specific prefix– Example: packet with destination of 10.1.1.1/32 is sent to the router

announcing 10.1/16 rather than the router announcing 10/8.

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IP route lookup• Based on destination IP address

10/8 announced from here

10.1/16 announced from here

Packet: DestinationIP address: 10.1.1.1

10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..

R2’s IP routing table

R1 R2

R3

R4

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IP route lookup:Longest match routing• Based on destination IP address


10.1.1.1 && FF.0.0.0vs.

10.0.0.0 && FF.0.0.0Match!

10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..



R1 R2

R3

R4


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10.1.1.1 && FF.FF.0.0vs.

10.1.0.0 && FF.FF.0.0Match as well!

10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..




R1 R2

R3

R4


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10.1.1.1 && FF.0.0.0vs.

20.0.0.0 && FF.0.0.0Does not match!

10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..




R1 R2

R3

R4


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10.1.1.1 && FF.0.0.0vs.

30.0.0.0 && FF.0.0.0Does not match!

10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..




R1 R2

R3

R4


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10/8 ® R310.1/16 ® R420/8 ® R530/8 ® R6…..


Longest match, 16 bit netmask



R1 R2

R3

R4


4242

RIBs and FIBs• FIB is the Forwarding Table

– It contains destinations and the interfaces to get to those destinations– Used by the router to figure out where to send the packet– Careful! Some people still call this a route!

• RIB is the Routing Table– It contains a list of all the destinations and the various next hops used

to get to those destinations – and lots of other information too!– One destination can have lots of possible next-hops – only the best

next-hop goes into the FIB

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Explicit versus Default Routing• Default:

– simple, cheap (cycles, memory, bandwidth)– low granularity (metric games)

• Explicit (default free zone)– high overhead, complex, high cost, high granularity

• Hybrid– minimise overhead– provide useful granularity– requires some filtering knowledge

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Routing Policy• Used to control traffic flow in and out of an ISP network

• ISP makes decisions on what routing information to accept and discard from its neighbours– Individual routes– Routes originated by specific ASes– Routes traversing specific ASes– Routes belonging to other groupings

• Groupings which you define as you see fit

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Representation of Routing Policy• Routing and packet flows

AS 1 AS 2routing flow

packet flow

packet flow

accepts

announces

announces

accepts

For AS1 and AS2 networks to communicate• AS1 must announce to AS2• AS2 must accept from AS1• AS2 must announce to AS1• AS1 must accept from AS2

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Representation of Routing Policy

AS 1 AS 2

aut-num: AS1…import: from AS2

action pref=100;accept AS2

export: to AS2 announce AS1

aut-num: AS2…import: from AS1

action pref=100;accept AS1

export: to AS1 announce AS2

Basic concept

“action pref” - the lower the value, the more preferred the route

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Routing flow and Traffic flow• Traffic flow is always in the opposite direction of the flow of

Routing information– Filtering outgoing routing information inhibits traffic flow inbound– Filtering inbound routing information inhibits traffic flow outbound

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Routing Flow/Packet Flow:With multiple ASes

• For net N1 in AS1 to send traffic to net N16 in AS16:– AS16 must originate and announce N16 to AS8.– AS8 must accept N16 from AS16.– AS8 must forward announcement of N16 to AS1 or AS34.– AS1 must accept N16 from AS8 or AS34.

• For two-way packet flow, similar policies must exist for N1

AS 1

AS 8

AS 34

AS16

N16

N1

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Routing Flow/Packet Flow:With multiple ASes

• As multiple paths between sites are implemented it is easy to see how policies can become quite complex.

AS 1

AS 8

AS 34

AS16

N16

N1

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Routing Protocols• Routers use “routing protocols” to exchange routing

information with each other– IGP is used to refer to the process running on routers inside an ISP’s

network– EGP is used to refer to the process running between routers

bordering directly connected ISP networks

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What is an IGP?• Interior Gateway Protocol

• Within an Autonomous System• Carries information about internal infrastructure prefixes

• Two widely used IGPs in service provider network:– OSPF– ISIS

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Why Do We Need an IGP?• ISP backbone scaling

– Hierarchy– Limiting scope of failure– Only used for ISP’s infrastructure addresses, not customers or

anything else– Design goal is to minimise number of prefixes in IGP to aid scalability

and rapid convergence

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What is an EGP?• Exterior Gateway Protocol

• Used to convey routing information between Autonomous Systems

• De-coupled from the IGP

• Current EGP is BGP

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Why Do We Need an EGP?• Scaling to large network

– Hierarchy– Limit scope of failure

• Define Administrative Boundary

• Policy– Control reachability of prefixes– Merge separate organisations– Connect multiple IGPs

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5555

Administrative Distance• method used for selection of route priority of IP routing

protocol, the lowest administrative distance is preferred– Manually entered routes are preferred from dynamically learned

routes• Static routes• Default routes

– Dynamically learned routes depend on the routing protocol metric calculation algorithm and default metrics values the smallest metric value are preferred

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Administrative Distance Chart (Cisco)

Routed Sources Default DistanceConnected interface 0Static route out an interface 0Static route to a next hop 1External BGP 20IGRP 100OSPF 110IS-IS 115RIP v1, v2 120EGP 140Internal BGP 200Unknown 255

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IP ADDRESSING

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Where do IP Addresses come from?

Standards

Allocation

Allocation

Assignment

End user

RIRs

LIR/ISP

6060

IPv4 Addresses• 32-bits long

232 or 4,294,967,296 possible addresses

• written in dotted-decimal format0.0.0.0 – 255.255.255.255

• Some are used for public, and some for private networks– Public IP addresses MUST be unique

11000000 10110000 00001111 00110010

192. 168. 15. 50

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Examples• Change from binary notation to dotted-decimal format:

1. 10000001 00001011 00001011 111011112. 11000001 10000011 00011011 111111113. 11100111 11011011 10001011 01101111

• Are these valid IPv4 addresses?1. 203.176.111.252. 297.0.67.1293. 4.100.5.2314. 100.00.10110.1111

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IP Addressing issues• Exhaustion of IPv4 addresses

– Wasted address space in traditional subnetting– Limited availability of /8 subnets address

• Internet routing table growth– Size of the routing table due to higher number prefix announcement

• Tremendous growth of the Internet– Management issues– Unstructured and wasteful distribution

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IP Addressing Solutions• Subnet masking and summarization

– Variable-length subnet mask definition– Hierarchical addressing– Classless Inter-domain Routing (CIDR)– Routes summarization (RFC 1518)

• Private address usage (RFC 1918)– Network address translation (NAT)

• Development of IPv6 address

6464

Variable Length Subnet Mask (VLSM)• Allows the ability to have more than one subnet mask within

a network

• Allows re-subnetting– create sub-subnet network address

• Increase the routes capability– Addressing hierarchy– Summarisation

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Subnetting Example• Subnet 192.168.0.0/24 into smaller subnet

– Subnet mask with /27 and /30 (point-to-point)

192.168.1.0/24

192.168.0.32/27

192.168.0.64/27

192.168.0.96/27

192.168.0.1/30

192.168.0.5/30

192.168.0.9/30

192.168.2.0/24

192.168.0.0/16

6666

Subnetting Example

• Subnet 192.168.0.0/24 into smaller subnet– Subnet mask with /30 (point-to-point)Description Decimal Binary

Network Address

192.168.0.0/30 x.x.x.00000000

1st valid IP 192.168.0.1/30 x.x.x.00000001

2nd valid IP 192.168.0.2/30 x.x.x.00000010

Broadcast address

192.168.0.3/30 x.x.x.00000011

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Subnetting Example

• Subnet 192.168.0.0/24 into smaller subnet– Subnet mask with /27Description Decimal Binary

Network Address

192.168.0.32/27 x.x.x.00000000

Valid IP range 192.168.0.33 - 192.168.0.62

x.x.x.00000001

x.x.x.00000010

Broadcast address

192.168.0.63/30 x.x.x.00011111

6868

Subnetting Example

• Subnet 192.168.0.0/24 into smaller subnet– Subnet mask with /27

Description Decimal VLSM Host Host range

1st subnet 192.168.0.0/27 x.x.x.000

00000

0-31

2nd subnet 192.168.0.32/27 x.x.x.001 31-63

3rd subnet 192.168.0.64/27 x.x.x.010 64-95

4th subnet 192.168.0.96/27 x.x.x.011 96-127

n = 5 (n is the remaining subnet bits )2n – 5 = 30 host per subnet

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Subnetting Example1. You have an IP range of 192.168.5.0/24. You need 20

subnets with 5 hosts per subnet. Find the host addresses for each subnet.

a) _________________b) _________________c) _________________

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Subnetting Example2. Given the IP address 172.16.10.22 with netmask

255.255.255.240a) What is the subnet IP range?b) What is the broadcast IP address?c) Find all valid IP addresses for this range

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Addressing Hierarchy

Core192.168.32.0/19

Network Number192.168.0.0/16

Distribution/Core192.168.32.0/21

Access/Distribution192.168.48.0/21

UpstreamA

IXPA

IXPB

UpstreamB

POPPOP

Core

Border

Distribution

Access Access

7272

Prefix routing / CIDR • Prefix routing commonly known as classless inter domain routing

(CIDR)– It allows prefix routing and summarisation with the routing tables of the

Internet

• RFCs that talks about CIDR– RFC 1517 Applicability statement for the implementation of CIDR– RFC 1518 Architecture for IP address allocation with CIDR– RFC 1519 CIDR : an address assignment and aggregation strategy– RFC 1520 Exchanging routing information access provider boundaries in

a CIDR environment

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CIDR solution advantage• CIDR offers the advantage of reducing the routing table size of the

network by summarising the ISP announcement in a single /22 advertisement

192.168.3.0/24

192.168.0.0/24

192.168.1.0/24 192.168.0.0/22

192.168.0.0/24

192.168.1.0/24

192.168.3.0/24

192.168.2.0/24Internet

A

B

C

D

192.168.2.0/24

7474

Summarisation example• Router C summarises its networks (2 x/24) before announcing to its

neighbors (routers B and D)

• Router A combined the networks received from B, C, D and announce it as single /16 routing to Internet

192.168.64.0/20

192.168.128.0/20

192.168.0.0/24 192.168.0.0/16

192.168.128.0/20

192.168.0.0/23

192.168.64.0/20

192.168.1.0/24Internet

A

B

C

D

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Route summarisation• Subnet 192.168.0.0/24 and 192.168.1.0/24 combining then

to become a bigger block of address “/23”

Network Subnet Mask Binary

192.168.0.0 255.255.255.0 x.x.00000000.x

192.168.1.0 255.255.255.0 x.x.00000001.x

Summary 192.168.0.0/23 x.x.00000000.x

192.168.0.0 255.255.254.0 x.x.00000000.x

7676

Route Summarisation• Allows the presentation of a series of networks in a single

summary address.

• Advantages:– Faster convergence– Reducing the size of the routing table– Simplification– Hiding Network Changes– Isolate topology changes

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IP ADDRESS MANAGEMENT

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Internet Registry Structure

8080

• Asia-Pacific Network Information Centre

• One of five Regional Internet Registry (RIRs) charged with ensuring the fair distribution and responsible management of IP addresses and related resources

• A membership-based, not-for-profit organization

• Industry self-regulatory body– Open– Consensus-based– Transparent

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Where is the APNIC Region?

82

Resource distribution- IP addresses- AS numbers

Registration services- reverse DNS- Internet routing

registry- resource certification- whois registry

What does APNIC do?APNIC servicesMembers

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83

Policy development

Capacity building- training- workshops- conferences- fellowships- grants

Infrastructure- root servers- IXPs- engineering

assistance

What does APNIC do?APNIC supportsthe Asia Pacific region

84

Original research

Data collection and measurements

Publications

Local/regional/global events

Government outreach

Intergovernmental & technical organizations collaboration

Internet security

What does APNIC do?APNIC collaborateswith the Internetcommunity

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APNIC in the Internet Ecosystem

Industryassociations

NGOs

Nameregistries

Access

Standardsbodies

Governments/Regulators

At-largecommunities

INTERNETUSERS

Applications

ContentENABLERS

PROVIDERSOperator

groups

Numberregistries

APNIC is one of five RIRs

ASIA PACIFIC REGION

Support

APNIC MEM

BERS

INTE

RNET

COM

MUNITY

Service

Colla

bora

tio

n

Resource distribution- IP addresses- AS numbers

Registration services- reverse DNS- Internet routing

registry- resource certification- whois registry Policy development

Capacity building- training- workshops- conferences- fellowships- grants

Infrastructure- root servers- IXPs- engineering

assistance

Original research

Data collection and measurements

Publications

Local/regional/global events

Government outreach

Intergovernmental & technical organizations collaboration

Internet security

8686

APNIC from a Global Perspective

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8787

APNIC in the Asia Pacific

ISOC chapters

88

Global Policy Coordination

The NRO is a coordinating body for the five regional Internet registries (RIRs)

www.nro.net

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89

Global Policy Coordination

The purpose of the Address Supporting Organization (ASO) is to review and develop recommendations on Internet Protocol (IP) address policy

and to advise the ICANN Board.

ASOICANN Address Supporting Organization

https://aso.icann.org/

90

IRM Objectives

- Efficient use of resources- Based on demonstrated need

Conservation

- Limit routing table growth- Support provider-based routing

Aggregation

- Ensure uniqueness- Facilitate trouble shooting

Registration

Uniqueness, fairness and consistency

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How IP Addresses are Delegated

Member (LIR)

LIR customer

Regi

stry

Rea

lm

Ope

rato

rs R

ealm

Customer / End User

delegates to customers

delegates to APNIC member

Member Allocation

/26 /27 /25

Customer Assignments

Sub Allocation

/26 /27

APNIC Allocation

/8

/24

APNIC

92


ISPAllocation


ISP

Portable and Non-Portable• Portable Address

– Provider-Independent (PI)– Assigned by RIR to end-user– Keeps addresses when changing

ISP– Increases the size of routing tables

• Non-portable Address– Provider-aggregatable (PA)– End-user gets address space from

LIR– Must renumber if changing upstream

provider– Can be aggregated for improved

routing efficiency

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IPv6 Address Management Hierarchy

Describes “portability” of the address space

/12 APNIC Allocation

Portable

Portable

/48 Assignment /48 - /64 Assignment

APNIC Allocation

/48 - /64Assignment

Non-Portable Non-Portable

/40

/32 Member Allocation

Non-Portable

/12

Sub-allocation

94

Aggregation and Portability Aggregation No Aggregation

(non-portable assignments)

(4 routes) (21 routes)

(portable assignments)

INTERNET INTERNET

ISP A ISP B ISP B

ISP C ISP D

ISP A

ISP C ISP D

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Policy Development• Creating a policy environment that supports the region’s

Internet development

• Developed by the membership and broader Internet community

96

You are part of the APNIC community!

APNIC Internet Community

Global Internet Community

Open forum in the Asia Pacific

APNICMembers

A voice in regional Internet operations through participation in APNIC

IETF Individuals

NationalNOG

RegionalNOGAPAN

ISOC

ISPAssociations

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Policy Development Process

All decisions & policies documented & freely available to anyone

Internet community proposes and approves policy

Open

TransparentBottom up

Anyone can participate

98

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DNS & REVERSE DNS

100100

Domain Name System• A lookup mechanism for translating objects into other

objects– Mapping names to numbers and vice versa

• A globally distributed, loosely coherent, scalable, reliable, dynamic database

• Comprised of three components– A “name space”– Servers making that name space available– Resolvers (clients) query the servers about the name space

• A critical piece of the Internet infrastructure

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IP Addresses vs Domain Names

The Internet

2001:0C00:8888::My Computer www.apnic.net2001:0400::

www.apnic.net202.112.0.462001:0400::

DNS

102102

This feature still exists:[Unix] /etc/hosts

[Windows] c:\windows\hosts

Old Solution: hosts.txt• A centrally-maintained file, distributed to all hosts on the

Internet

• Issues with having just one file– Becomes huge after some time– Needs frequent copying to ALL hosts– Consistency– Always out-of-date– Name uniqueness– Single point of administration

// hosts.txtSERVER1

128.4.13.9WEBMAIL

4.98.133.7FTPHOST

200.10.194.33

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DNS Features• Global distribution

– Shares the load and administration

• Loose Coherency– Geographically distributed, but still coherent

• Scalability – can add DNS servers without affecting the entire DNS

• Reliability• Dynamicity

– Modify and update data dynamically

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DNS Features• DNS is a client-server application

• Requests and responses are normally sent in UDP packets, port 53

• Occasionally uses TCP, port 53– for very large requests, e.g. zone transfer from master to slave

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Root.

.org .net .com .au

.edu.au

example.edu.au

.gov

.jp

.tv

.inx.y.z.a

www.example.edu.au

a.b.c.d

e.f.g.h

i.j.k.l

m.n.o.pw.x.y.z.

p.q.r.s

“Ask a.b.c.d”“Ask e.f.g.h”

“Ask i.j.k.l”

“Go to m.n.o.p”

localdns

www.example.edu.au?“go tom.n.o.p”

www.example.edu.au?

www.example.edu.au?

www.example.edu.au?

www.example.edu.au?

Querying the DNS – It’s all about IP!

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The DNS Tree HierarchyRoot.

net jporg com arpa au

whois

edu

bnu

iana

www www

…

www wasabi

ws1 ws2

edu comnet

abc

www

apnicgu

www

FQDN = Fully Qualified Domain Name

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Domains• Domains are “namespaces”

• Everything below .com is in the com domain• Everything below apnic.net is in the apnic.net domain and

in the net domain

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NET Domain

APNIC.NET Domain

AU Domain

www.def.edu.au?

Root.

net org com arpa au

whois

iana

wwwwww wasabi

ws1 ws2

edu comnet

abc

www

apnic

def

www

Domains

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Delegation• Administrators can create subdomains to group hosts

– According to geography, organizational affiliation or any other criterion

• An administrator of a domain can delegate responsibility for managing a subdomain to someone else– But this isn’t required

• The parent domain retains links to the delegated subdomain– The parent domain “remembers” to whom the subdomain is

delegated

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Zones and Delegations• Zones are “administrative spaces”

• Zone administrators are responsible for a portion of a domain’s name space

• Authority is delegated from parent to child

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NET Domain

APNIC.NETDomain

NET Zone

TRAINING.APNIC.NET Zone

APNIC.NET Zone doesn’t include TRAINING.APNIC.NETsince it has been “delegated”

APNIC.NET Zone

Root.

net org com arpa

whois

iana

wwwwww training

ns1 ns2

apnic

Zones

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Name Servers• Name servers answer ‘DNS’ questions

• Several types of name servers– Authoritative servers

• master (primary)• slave (secondary)

– Caching or recursive servers• also caching forwarders

• Mixture of functions

Primary

Secondary

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Root Servers• The top of the DNS hierarchy

• There are 13 root name servers operated around the world– [a-m].root-servers.net

• There are more than 13 physical root name servers– Each rootserver has an instance deployed via anycast

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Root Servers

http://root-servers.org/

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Root Server Deployment at APNIC• Started in 2002, APNIC is committed to establish new root

server sites in the AP region

• APNIC assists in the deployment providing technical support.

• Deployments of F, K and I-root servers in – Singapore, Hong Kong, China, Korea, Thailand, Malaysia, Indonesia,

Philippines, Fiji, Pakistan, Bangladesh, Taiwan, Cambodia, Bhutan, and Mongolia

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What is Reverse DNS?• Forward DNS maps names to numbers

server.apnic.net è203.0.113.1

• Reverse DNS maps numbers to names203.0.113.1 è server.apnic.net

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Uses of Reverse DNS• Service denial

– That only allow access when fully reverse delegated eg. anonymous ftp

• Diagnostics– Assisting in network troubleshooting (ex: traceroute)

• Spam identifications– Reverse lookup to confirm the source of the email– Failed lookup adds to an email’s spam score

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Reverse DNS TreeMapping numbers to names - ‘reverse DNS’

22.64.202.in-addr.arpa.

apnic

whois www wwwtraining

ws1 ws2

202

64

22

203 204 210

iana in-addr

ROOT

net org com arpa

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119

Reverse DNS Tree – with IPv6

apnic

202

64

22

203

ip6

IPv6 addresses

iana in-addr

ROOT

net org com arpa int

RFC3152

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Reverse Zone Example$ORIGIN 1.168.192.in-addr.arpa.@ 3600 IN SOA test.company.org. ( sys.admin.company.org.

2002021301 ; serial1h ; refresh30M ; retry1W ; expiry3600 ) ; neg. answ. ttl

NS ns.company.org.NS ns2.company.org.

1 PTR gw.company.org.router.company.org.

2 PTR ns.company.org.;auto generate: 65 PTR host65.company.org$GENERATE 65-127 $ PTR host$.company.org.

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Managing Reverse DNS• APNIC manages reverse delegation for both IPv4 and IPv6

• Before you register your domain objects, you need to ensure that your reverse zones have been configured and loaded in your name servers

• APNIC does not host your name servers or configure your reverse zone files

• APNIC only delegates the authority of your reverse zones to the name servers you provide through your domain objects

www.apnic.net/dns

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Reverse Delegation for IPv4• Reverse delegation for IPv4 is based on octet boundaries

• /24 Delegations– Address blocks should be delegated– At least one name server

• /16 Delegations– Same as /24 delegations– APNIC delegates entire zone to member

• < /24 Delegations– Read “classless in-addr.arpa delegation”– Not supported

RFC2317

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Reverse Delegation for IPv6• Reverse delegation for IPv4 is based on nibble boundaries

• /32 delegation– One domain object

• /48 delegation– One domain object

• /35 delegation– Divide into two /36 (closest 4-bit boundary)– Two separate domain objects

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APNIC & LIR Responsibilities• APNIC

– Manage reverse delegations of address block distributed by APNIC – Process organisations requests for reverse delegations of network

allocations

• Organisations / LIR– Be familiar with APNIC procedures– Ensure that addresses are reverse-mapped– Maintain nameserver(s) for allocations– Keep accurate records in the database– Keep reverse DNS current with the Whois DB

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Reverse Delegation Procedures• Domain objects can be updated through MyAPNIC

• Nameserver/domain must be configured before domain objects are created

http://apnic.net/create-domain

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Reverse Delegation Procedures

Input your IP address block here

At least one DNS server (FQDN)

Maintainer password

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Whois Domain Object

domain: 28.12.202.in-addr.arpaDescr: in-addr.arpa zone for 28.12.202.in-addr.arpaadmin-c: NO4-APtech-c: AIC1-APzone-c: NO4-APnserver: cumin.apnic.netnserver: tinnie.apnic.netnserver: tinnie.arin.netmnt-by: MAINT-APNIC-APmnt-lower: MAINT-AP-DNSchanged: [email protected] 20021023changed: [email protected] 20040109changed: [email protected] 20091007changed: [email protected] 20111208source: APNIC

Reverse Zone

Contacts

Nameservers

Maintainers

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Thank You!END OF SESSION

1.internet fundamentals nr

Documents