Network Layer Protocols and Internet Protocol (IP) · 2017-03-14 · Network Layer Protocols and...

Network Layer Protocols and Internet Protocol (IP)

Suguru Yamaguchi Nara Institute of Science and Technology

1 2011 Network Information 1 / 05

Network Layer Features  Basic model  Node identification  Node aggregation  End-to-end Packet delivery  Broadcast・Multicast

 Failure isolation and Failure recovery  Connecting heterogeneous datalinks

2011 Network Information 1 / 05 2


OSI 7 Layer Reference Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

NFS

XDR

Sun RPC

TCP

IP

IEEE802.3

Ethernet Coax

ES (End System) ES (End System)

Upper Layer Protocol

IS (Intermediate System)

Physical connection Physical connection

Connecting heterogeneous datalinks


Network

Gateway

The gateway forwards IP packets as an intermediate system according to the routing structure. Connecting directory with datalink in same network.


TCP/IP as a Layered Protocol Architecture

Physical

Network Interface

IP

TCP

Application

Physical

Network Interface

IP

TCP

Application

Physical

Network Interface

IP

IP realizes the end-to-end communication


TCP/IP as a Layered Protocol Architecture

② The layer upper to the IP protocol defines the service. Thereby, it does not matter what comes below the datalink layer.

①Service relationship is defined by service provider.

Node identification


•  Globally unique address space •  Address space and delegation of authority •  Network identification and host identification •  Address class

Address class Address space that delegates authority to the layers

Identifying network Identifying host

0xDD 0xA3 0x4A 0x7F

163.221.74.127/24

163 221 74 127

Network area is ２４ bits

Prefix length

例） IPv4 address

11

Node aggregation: from efficiency perspectives  163.221/16  163.221.52/24  163.221.127.0/21  ...  Prefix length = Binary tree level  Simple expression → Fast and memory-saving → Especially in relay node...

2011 Network Information 1 / 05

Address aggregation  Aggregating contiguous network blocks

12

Host 00 Network Number

24




C

C

C

C

Prefix

22

４C


Address aggregation

13

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [2] 192.24.34.0/23 : 11000000.00011000.0010001- -------- [3] 192.24.32.0/23 : 11000000.00011000.0010000- --------

[4] 192.24.16.0/20 : 11000000.00011000.0001---- -------- [5] 192.24. 0.0/21 : 11000000.00011000.00000--- -------- [6] 192.24. 8.0/22 : 11000000.00011000.000010-- -------- [7] 192.24.12.0/22 : 11000000.00011000.000011-- --------

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [8] 192.24.32.0/22 : 11000000.00011000.001000-- -------- [4] 192.24.16.0/20 : 11000000.00011000.0001---- --------

[5] 192.24. 0.0/21 : 11000000.00011000.00000--- -------- [9] 192.24. 8.0/21 : 11000000.00011000.00001--- --------

Aggregate; ‏[2] + [3] = [8] (.34/23 + .32/23) [6] + [7] = [9] (.8/22 + .12/22)


15

End-to-end packet delivery

 Network Layer “Cloud”.  Hosts are present at the cloud edge.  Identified uniquely by IPv4 address.

Network Layer

163.221.5.5

163.221.4.4

163.221.3.3


16

Graph representation of networks  datalink layer

•  Network Layer l  Arbitrary topology l  Any difference with bridges? What if we label the graph...


17

Hierarchy perspective: who carries the ladder?

Datalink Layer Datalink Layer

Network Layer From datalink layer to network layer: Native to datalink layer Ex: LLC/SNAP, NLPID From network layer

to datalink layer: Native to network layer Ex) ARP (IPv4)‏ ND (IPv6)


18

Network to datalink: Address Resolution Protocol： ARP(1)

 A → B: “M” –  a → all stations: “where is B” –  b → a: “B is at b” –  a → b: “A → B: “M””

A B C a b c Data-link layer

Network layer

RFC826


19

Network to datalink: the case of routed networks ： ARP(2)

 A → C: “M” –  a → all stations: “where is R” –  r → a: “R is at r” –  a → r: “A → C: “M””

l  r → all stations: “where is C” l  c → r: “C is at c” l  r → c: “A → C: “M””

A B a b

C D c d

R r

Data-link layer Network layer


20

Network to datalink: the case of bridged networks ： ARP(3)

 A → C: “M” –  a → all stations: “where is C” –  c → a: “C is at a” –  a → c: “A → C: “M””

A B a b

C D c d

T t



21

Datalink to network layer  Several network layer protocols are multiplexed to a

single datalink layer.  Multiplexing, de-multiplexing

IPv4 IPv6 ....

Ethernet

IPv4 IPv6 ....

Ethernet Datalink

Network

?


Ethernet, IEEE802.3, 802.2LLC, …


Dst addr Src addr Type FCS DATA (variable)

Length FCS DATA (variable)

Length FCS DATA (variable)

DSAP SSAP CTL DATA (variable) FCS

Protocol ID Type DATA (variable) FCS

6 6 2

1 1 1

2 3

4

(head is 0xFFFF）

Ethernet2

IEEE802.3 (Length < 0x05DC)

IEEE802.3 Raw

IEEE802.2 LLC

SNAP

23

Datalink to network: De-multiplexing with LLC(2):

Source SAP Address Information

1

Control

1 or 2 bytes

Destination SAP Address Source SAP Address

I/G

7 bits 1

C/R

7 bits 1

I/G = Individual or group address C/R = Command or response frame

Destination SAP Address

1 byte

SAP address examples: 06 IP packet E0　Novell IPX FE　OSI packet AA　SubNetwork Access protocol (SNAP)


24

De-multiplexing with LLC/SNAP

MAC Header FCS

AA AA 03 LLC PDU 1 1 1

Information SNAP Header

Type ORG

SNAP PDU

3 2


Implementing the communication model  Unicast

–  Peer to Peer communication –  Source and destination address allocation

–  Example p.16, 17, 18 is Unicast

 Broadcast

 Multicast


Broadcast –  Sending to all hosts running in the same transmission medium

(datalink). •  Broadcast communication availability depends on the datalink. •  Many datalinks do not support broadcast communication.

–  Does not guarantee a perfect broadcast. •  Passive hosts will not receive the broadcast. •  Processing received data depends on the processes run by

receiving hosts.

 IP broadcast  Link-layer broadcast


28

Bootstrapping with broadcast  Broadcast communication in multi-access

network –  It is absolutely necessary to resolve address from

network layer to datalink layer. –  Automatic configuration is absolutely necessary.

A B C a b c Data-link layer

Network layer

•  Bootstrap A: l  a → all stations:

“who is router” l  r → a:

“router R is at r”

R r


Selective broadcasting  Multicast

–  Multi-point to Multi-point communication –  Selective broadcasting

–  Membership •  If host is not a member, it won’t be able to listen to

communications within the group. –  Membership management –  Group Management

 IP multicast  Link-layer multicast


31

What if...?

Application

Presentation

Session

Transport

Network

Data Link

Physical

physical connection

Application

Presentation

Session

Transport

Network

Data Link

Physical

→ Failure isolation and Failure recovery 2011 Network Information 1 / 05

32

Failure isolation: ICMP

 Failure occuring below the datalink layer →Dropping a Packet

 In the case a packet did not reach its destination –  Destination Unreachable –  Returning to the source address.

RFC792

failure

ICMP Destination Unreachable


33

Failure isolation: ICMP(2)  End-to-end reachability verification, faulty section

judgement. –  Echo Request, Echo Reply

Application Presentation

Session Transport Network

Data Link Physical

Application Presentation

Session Transport Network

Data Link Physical


Connecting heterogeneous datalinks  Because of heterogeneity...

–  Address architecture is different→Resolving with ARP. –  Multiplexing method is different→Resolving with LLC/SNAP

–  Transmission speed is different •  →Resolving with buffer

–  Maximum Transmission Unit (MTU) size is different •  →Fragmentation


36

Connecting heterogeneous datalinks: fragmentation and reassembly  Fragmentation ：

–  Fragmenting a packet and keeping fragments within a maximum frame length.

 Reassembly： –  Reconstructing the fragmented packet at the destination node.

MTU = 1520 MTU = 9128


37

Implementing Fragmentation and Reassembly： IPv4 Header  Flags = {0, MF, DF}  Fragment offset: 13 bits

8 31 0 4 16

Ver.

Option (if any)‏

IHL Type of Service Total Length (in Octet)‏

Identification Flags Fragment Offset

Time to Live Protocol Header Checksum

Source Address

Destination Address


Conclusion  Basic model  Node identification  Node aggregation  End-to-end Packet delivery  Broadcast・Multicast



Road to IPv6


40

Ongoing growth

Active BGP FIB entries @ AS65000, Feb. 2010, Source: BGP Reports, available online. At http://bgp.potaroo.net/ 2011 Network Information 1 / 05

Problem  Drastic growth of Internet

– address depletion and drastic growth of routes

– New adaptation field, New requirement

 Urgent problem – Address and Route F Route Aggregation

 Radical solution F New IP protocol – IPv6


Technical Criteria for Choosing IPng (RFC1726)

 Five basic principles – Simple structure – Single protocol – Applicable for a long time. – Used widely – Cooperative anarchy (preserve the

decentralized and decoupled nature of the Internet)



 Scale –  End systems number is over 1012 –  Distinct networks number is over 109

 Topology flexibility –  Not assuming a specific network topology.

 Tough service –  Network service, routing and network control

 Transition plan –  Easy transition plan from IPv4

 Media (link) independent



 Configuration –  Auto-configuration

 Publication of specifications –  RFC Standard track

 Other features –  Security –  Mobile host and network –  Multicast


SeIecting IPng: History

 1991 Draft is publicly announced by IAB.  1992 IPng section meeting starts discussion.

–  TUBA(TCP and UDP over Bigger Address)‏ –  CATNIP(Common Architecture for the Internet)‏ –  SIPP(Simple Internet Protocol Plus)‏

 1994 Decision to base the specification on SIPP.  1995 Decision of an IPv6 specification.


IPv6


Difference between IPv6 and IPv4

 Expansion of the address space –  from 32bit to 128bit.

•  32bit 4,294,967,296 (4billion)‏ •  128bit

340,282,366,920,938,463,463,374,607,431,768,211,456

 Address architecture –  Hierarchic structure –  Introduction of the concept of scope –  Clear definition of address classes

 Multicast Standardization –  Discontinuation of broadcast


Difference between IPv6 and IPv4(cont.)

 Able to deal with high-speed networks –  Simplified header format

•  Suppression of unused fields •  Static length •  Discontinuation of checksums •  Discontinuation of IP header options

–  Discontinuation of en-route packet fragmentation

48

Router HOST HOST


Difference between IPv6 and IPv4(cont.)

 Link layer and network layer address resolution –  ARP -> NDP (Neighbor Discovery Protocol)‏ –  Unreachability detection

 Security –  IPsec as a standard

 Flexibility –  IP extension header

•  MobileIPv6 •  IPsec


NDP(Neighbor Discovery Protocol)  NDP features

–  Prefix Discovery –  Address Autoconfiguration –  Next-hop determination –  Neighbor Unreachability –  Duplicate Address Detection

 Implementations –  Multicast –  Implementing as a ICMP and Having a following packet type

•  Router Solicitation •  Router Advertisement •  Neighbor Solicitation •  Neighbor Advertisement •  Redirect


NDP  First, A is link local address.  a→all stations : “where is R”  r→a : “R is at r”  a→r : “I’m a”  r→a : “a is A and gateway is r”


A B a b

R r


Differences between NDP and ARP  ARP

–  To get a data-link layer address from network layer address.

 In NDP, This feature is implement as a one of NDP functions. –  Address Resolution


IPv4 Header

53

Ver HL TOS Total Length

Identification Flag Fragment Offset

TTL Protocol Header Checksum

Source Address

Destination Address

Options Padding

IPv4

Fields in gray are suppressed or renamed in IPv6.


IPv6 ヘッダ

54

Ver Traffic Class Flow Label

Payload Length Next Header Hop Limit

Source Address

Destination Address

IPv6

• Fields in red are renamed from IPv4 specifications

• Packet length has been fixed


IPv6 - Internet’s True Form

 Expansion of address space –  Restoration of the End-to-End model

 Aggregatable address system  Features that accommodate new requirements

–  Multicast –  Security –  Auto-configuration

 Auto-configuration –  Standardization of an automatic address configuration system –  Network renumbering


IPv6 Address Expression

 Expressing 128 bits in hexadecimal  Splitting every 4 digits using “:”

–  3ffe:501:100c:e320:2e0:18ff:fe98:936d

 Allowing to skip consecutive “0” sequence –  3ffe:0501:100c:e320:0000:0000:0000:0001 →

3ffe:501:100c:e320::0001


IPv6 Address Structure

 Separating network prefix and interface ID. –  Network prefix (Upper 64 bits)‏

•  For the moment allocation based on an aggregatable address system. –  Host ID (Lower 64 bits)‏

•  EUI-64 •  In the case of Ethernet, decision based on MAC address


IPv6 Address Structure (cont.)‏

58

Interface ID

64bit 64bit

Network Prefix

IPv6 : 2001:218:1800::/48 IPv4 : 45.0.0.0/8

2001:218:1800:e100::/64 2001:218:1800:e200::/64 45.0.1.0/24


Address Class

 Unicast Address –  Assigned to a single interface.

 Multicast Address

–  Assigned to several interfaces and delivered to all these interfaces.


Address Class (cont.)

 Loopback Address –  Expressing oneself address ::1

 IPv4 compatibility address –  ::IPv4 address –  ::203.178.142.1 –  Address used for auto-tunnelling

 IPv4-mapped address –  ::ffff:IPv4 address –  ::ffff:203.178.142.1 –  Address expression to show a node implements IPv4 only


Format Prefix

Usage Prefix Occupation Reserved 0000 0000 1/256 Unassigned 0000 0001 1/256 Reserved for NSAP Allocation 0000 001 1/128 Reserved for IPX Allocation 0000 010 1/128 Unassigned 0000 011 1/128 Unassigned 0000 1 1/32 Unassigned 0001 1/16 Aggregatable Global Unicast Address 001 1/8

Unassigned 010 1/8 Unassigned 011 1/8 Unassigned 100 1/8 Unassigned 101 1/8


Format Prefix (cont.)‏

Usage Prefix Occupation Unassigned 110 1/8 Unassigned 1110 1/16 Unassigned 1111 0 1/32 Unassigned 1111 10 1/64 Unassigned 1111 110 1/128 Unassigned 1111 1110 0 1/512 Link-Local Unicast Address 1111 1110 10 1/1024 Multicast Address 1111 1111 1/256

Unassigned is dealt with as Unicast from now on.


Concept of Scope

 Global address –  Valid single address used in the whole Internet

 Link-Local address –  Address valid only at the link scope –  fe80::1


Concept of Scope (cont.)‏

64

HOST HOST

Organization

Router

HOST

Link-local

Link-local

Global

Organization


Aggregatable Address System

65

n  Address assignment following the network topology

FP TLA ID RE NLA ID SLA ID Interface ID 3 13 13 6 13 16 64

FP Format Prefix RE Reserved TLA ID Top-Level Aggregation Identifier NLA ID Next-Level Aggregation Identifier SLA ID Site-Level Aggregation Identifier

FP TLA ID RE NLA ID SLA ID Interface ID 3 13 8 24 16 64

sub-TLA

RFC2374

RFC2450


Address Assignment

66

APNIC

WIDE

NAIST USM

2001:200::/29 - 2001:3f8::/29

2001:200::/35

2001:200:16a::/48 2001:200:703::/48

TLA　ID

sub-TLA

NLA　ID


TLA (Top Level Aggregator)‏

67

TLA ID RE

3 13 8 24

NLA ID FP

TLA ID

3 13 13 19

NLA ID FP SubTLA ID

Previous assignment

Current assignment

n Assigned from RIRs (ARIN, RIPE, APNIC) n /29 address space


 ISPs and organizations acquire addresses from TLA  Enabling to set a subnet  From /35 to /48 address spaces

NLA (Next Level Aggregator)‏

68

TLA ID RE

3 13 8 24

NLA ID FP

TLA ID NLA ID FP SubTLA ID

Previous assignment

3 13 13 19 2011 Network Information 1 / 05

Current assignment

SLA (Site Level Aggregator)‏

 Organizations acquire addresses from NLA.  From /49 to /64 address spaces

69

TLA ID NLA ID FP SubTLA ID

3 13 13 19　　　　　16

SLA ID


Address auto-configuration： Ethernet and IPv6 addresses

 The interface part is automatically generated using the MAC address.

 EUI-64 –  00:e0:18:98:93:6d (MAC address) →

2001:200:16a:e320:2e0:18ff:fe98:936d


Another Unicast Address

 Link Local Address –  Address valid at the link scope

fe80::2e0:18ff:fe98:936d

71

1111111010 10 bits 64 bits

00000.........0000 56 bits

interface Id


Multicast Address

72

11111111 8 bits 112 bits

flgs scope

4 4

group ID

0 reserved 1 node-local scope 2 link-local scope 5 site-local scope 8 organization-local scope E global scope F reserved

0000 permanent(defined)address 0001 temporary address


Defined Multicast Address

FF00:0:0:0:0:0:0:0 reserved FF01:0:0:0:0:0:0:0 reserved : FF0F:0:0:0:0:0:0:0 reserved FF01:0:0:0:0:0:0:1 All IPv6 nodes address (node-local) FF02:0:0:0:0:0:0:1 All IPv6 nodes address (link-local) FF01:0:0:0:0:0:0:2 All IPv6 routers address (node-local) FF02:0:0:0:0:0:0:2 All IPv6 routers address (link-local) FF02:0:0:0:0:0:0:C DHCP servers / relay agents FF02:0:0:0:0:1:x:x Solicited-Node address


Conclusion

 IPv6: Internet Protocol refactored –  Bigger address space –  Aggregation –  Multicast –  Auto-configuration

 Topics not covered here: –  Extensible headers –  Security –  Mobility –  Path MTU discovery –  Anycast –  Transition


Network Layer Protocols and Internet Protocol (IP) · 2017-03-14 · Network Layer Protocols and...

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Transcript of Network Layer Protocols and Internet Protocol (IP) · 2017-03-14 · Network Layer Protocols and...