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Lecture #17: Internet Network Lecture #17: Internet Network LayerLayer

C o n t e n t s C o n t e n t s

Internet Network layer Internet Network layer

IPv4 datagram formatIPv4 datagram format

IPv4 addressingIPv4 addressing

SubnettingSubnetting

Internet control protocols, ICMPInternet control protocols, ICMP

ARP, RARP & BOOTP, DHCPARP, RARP & BOOTP, DHCP

IPv6IPv6

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Internet Network LayerInternet Network LayerNetwork layer functions

• Connection control: establishment, maintaining and terminating network connections between source and destination open systems

• Routing: considerations associated with hop-by-hop services transparent to the underlying resources such as data link connections .

• Addressing: globally unique identification of a service access point of an end system (transparent to subnet technology (routers/LANs…) and topology (# of hops) including naming

Internet architecture • Ineternetwork of autonomous systems (AS)• backbones: high-bandwidth connections and fast routers• regional networks (midlevel)• LANs and ISP systems • internet protocol (IP) - transparent datagram exchange

from-end-to-end

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IPv4 - datagram formatIPv4 - datagram format IP DatagramIP Datagram 32 bits wide (4 Bytes) 32 bits wide (4 Bytes)

– IP HeaderIP Header (20 Bytes) (20 Bytes)• VersionVersion (currently #4) (currently #4)• IInternet nternet HHeader eader LLengthength ( (min value is 5, max min value is 5, max

FFhFFh))• Type of ServiceType of Service (QoS) (QoS)

Precedence (3b) [0..7]Precedence (3b) [0..7] DDelay elay TThroughputhroughput RReliabilityeliability

• Total Length datagramTotal Length datagram (bytes) - (bytes) - – maximum is 65,535 bytesmaximum is 65,535 bytes– may be fragmented before transmissionmay be fragmented before transmission

• IdentificationIdentification of the datagram at the of the datagram at the destination. All fragments of a datagram have destination. All fragments of a datagram have identical ID field. identical ID field.

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IP Header (cont.)IP Header (cont.)• FragmentationFragmentation

• Occurs often - all machine are required to receive Occurs often - all machine are required to receive fragments of 567 bytes or lessfragments of 567 bytes or less

• Identifier - Used by the receiver to identifies which Identifier - Used by the receiver to identifies which datagram this fragment belongs todatagram this fragment belongs to

• Flags: Don’t Frag, More Frag flagsFlags: Don’t Frag, More Frag flags• Fragment Offset:Fragment Offset:

• Indicates where in the datagram this fragment belongsIndicates where in the datagram this fragment belongs• Datagrams are segmented into increments/frags of 64 Datagrams are segmented into increments/frags of 64

bitsbits• 13 bits for offset value yields a maximum of 8192 13 bits for offset value yields a maximum of 8192

fragments per datagramfragments per datagram

• Time to liveTime to live: <32 or 64 hops, <255 sec: <32 or 64 hops, <255 sec• ProtocolProtocol: : Indicates the next level of protocolIndicates the next level of protocol

• TCP, UDP, ICMPTCP, UDP, ICMP

IP datagram formatIP datagram format

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IP Header (cont.)IP Header (cont.)– Header CRCHeader CRC

• Only over the header; recalculated at each hopOnly over the header; recalculated at each hop• Not actually a CRCNot actually a CRC

– Source AddressSource Address – Destination AddressDestination Address

• 223232 possible (= 4 294 967 296) possible (= 4 294 967 296) Options, Padding, DataOptions, Padding, Data

– Options ExamplesOptions Examples• Security - allows a security labelSecurity - allows a security label• Source Routing - path descriptionSource Routing - path description• Route RecordingRoute Recording• Stream ID - names reserved resources used for Stream ID - names reserved resources used for

stream service- buffersstream service- buffers• Time StampingTime Stamping

IP datagram formatIP datagram format

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IPv4 Addressing IPv4 Addressing ClassesClasses

– AA: 128 Networks, : 128 Networks, 16M Hosts - 16M Hosts - – BB: 16.3K Networks: 16.3K Networks 64K Hosts -64K Hosts -

University, large University, large OrganizationOrganization

– CC: 4.2 M: 4.2 M 256 Hosts256 Hosts

Numbers are assigned by the Numbers are assigned by the Network Information CenterNetwork Information Center (NIC)(NIC)

Dotted decimal notationDotted decimal notation– e.g., 130.50.4.2e.g., 130.50.4.2

– each number represents the decimal each number represents the decimal equivalent of 8 bitsequivalent of 8 bits

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IP AddressingIP Addressing Special IP AddressesSpecial IP Addresses

– All zeros: All zeros: this hostthis host– All zeros network address: All zeros network address: this (local) this (local)

networknetwork– All ones: All ones: broadcast on this networkbroadcast on this network

Subnet AddressingSubnet Addressing (Subnet Masks) (Subnet Masks)– In the above example, subnet address (6 bits) In the above example, subnet address (6 bits)

can formed from a (16 bit) host address, can formed from a (16 bit) host address, leaving 10 bits for host addressesleaving 10 bits for host addresses

– Results: Results: 6262 Subnets with Subnets with 10221022 hosts each hosts each

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““Subnets”Subnets”: : equal address-space fractions of an internet equal address-space fractions of an internet networknetwork

– the host address field is split in two parts - the host address field is split in two parts - • hosts (themselves) and hosts (themselves) and • subnet fieldsubnet field

– example:example: a B-class network [128.0 .. 191.255].XXX.XXX has 16b a B-class network [128.0 .. 191.255].XXX.XXX has 16b host-address field (i.e. total of 64K hosts’ space) that can be split host-address field (i.e. total of 64K hosts’ space) that can be split as follows:as follows:

• … … (less realistic)(less realistic)• 4:12 (s/h) 4:12 (s/h) 14 subnets of (4K-2=4094) hosts each 14 subnets of (4K-2=4094) hosts each • 5:11 (s/h) 5:11 (s/h) 30 subnets of (2K-2=2046) hosts each 30 subnets of (2K-2=2046) hosts each • 6:10 (s/h) 6:10 (s/h) 62 subnets of (1K-2=1022) hosts each 62 subnets of (1K-2=1022) hosts each • 7:9 (s/h) 7:9 (s/h) 126 subnets of 510 hosts each 126 subnets of 510 hosts each • 8:8 (s/h) 8:8 (s/h) 254 subnets of 254 hosts each (254 C-class networks!) 254 subnets of 254 hosts each (254 C-class networks!)• 9:7 (s/h) 9:7 (s/h) 510 subnets of 126 hosts each 510 subnets of 126 hosts each • … … (less realistic) (less realistic)

– routing effectsrouting effects::• shorter routing tables (i.e. more flexibility, easier corrections)shorter routing tables (i.e. more flexibility, easier corrections)• more routers in a IP networkmore routers in a IP network• the subnet is derived from the IP address by AND maskthe subnet is derived from the IP address by AND mask

SubnetsSubnets

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• ICMPICMP (Internet Control Message Protocol)(Internet Control Message Protocol)

• ARPARP (Address Resolution Protocol)(Address Resolution Protocol)– Allows a Host or Router to determine a hardware Allows a Host or Router to determine a hardware

address (MAC-level specified) for a given IP addressaddress (MAC-level specified) for a given IP address

– RTs of MAC-IP address are maintained by all Host - RTs of MAC-IP address are maintained by all Host -

RouterRouter• time sensitive - periodically purgedtime sensitive - periodically purged

• RARPRARP (Reserve Address Resolution Protocol)(Reserve Address Resolution Protocol)– Devices may not know their IP address: MAC - IP Devices may not know their IP address: MAC - IP

conversationconversation

– Usually provided by a serverUsually provided by a server

– Autoconfiguration: Host provide temporary IP Autoconfiguration: Host provide temporary IP

addresses - dynamically (RARP - locally, addresses - dynamically (RARP - locally, BOOTPBOOTP - -

globally)globally)

Internet Control Internet Control ProtocolsProtocols

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ICMPICMPICMP ICMP is the primary supervisory protocol in TCP/IPis the primary supervisory protocol in TCP/IP• Lets the Host and Routers know of the status of the Lets the Host and Routers know of the status of the

network around them - problems with routers, congestionnetwork around them - problems with routers, congestion• Network Status information provided to Hosts/Routers viaNetwork Status information provided to Hosts/Routers via

– Error messagesError messages– Queries from hosts (e.g., ping)Queries from hosts (e.g., ping)– Flow Control information (source squelch is implemented this way)Flow Control information (source squelch is implemented this way)– Routing (redirecting paths)Routing (redirecting paths)

• Message TypesMessage Types° Destination Unreachable - informs host that destination is either Destination Unreachable - informs host that destination is either

physically or logically unreachable.physically or logically unreachable.° Time Exceeded, Parameter - datagram lifetime expires (reassemble Time Exceeded, Parameter - datagram lifetime expires (reassemble

deadlock)deadlock)° Parameter Problem (rcvd an incorrect argument for a parameter), Parameter Problem (rcvd an incorrect argument for a parameter),

syntax or semantics syntax or semantics ° Redirect, Echo/reply - Test for different routeRedirect, Echo/reply - Test for different route° Source Squelch - sent by either destination Host (flow control) or Source Squelch - sent by either destination Host (flow control) or

Router (Congestion Control)Router (Congestion Control)° Timestamp request/reply - Test for delay characteristics Timestamp request/reply - Test for delay characteristics ° Information request/replyInformation request/reply° Address Mask - To address subnet more directlyAddress Mask - To address subnet more directly

• ICMP uses IP datagrams modified with a 64-bit headerICMP uses IP datagrams modified with a 64-bit header

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•ARPARP = Address Resolution Protocol= Address Resolution Protocol

•Maps IP addresses to MAC-specified addresses Maps IP addresses to MAC-specified addresses

(e.g. Ethernet 6 byte address) (e.g. Ethernet 6 byte address)

•RTs of MAC-IP address are maintained by all Host RTs of MAC-IP address are maintained by all Host

- Router- Router– better and more flexible than static configuration map better and more flexible than static configuration map

– time sensitive - periodically purgedtime sensitive - periodically purged

– cashing the map information avoids frequent repetition of cashing the map information avoids frequent repetition of

the broadcastingthe broadcasting

– host initiated broadcasting on boot up (- avoiding host initiated broadcasting on boot up (- avoiding

duplication of IP addresses)duplication of IP addresses)

•ARP/RARP has its own protocol frame ARP/RARP has its own protocol frame

structurestructure

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RARP & BOOTPRARP & BOOTP• RARPRARP = Reverse Address Resolution Protocol= Reverse Address Resolution Protocol

• Maps MAC-specified addresses to IP addresses e.g. Maps MAC-specified addresses to IP addresses e.g.

by booting diskless stationby booting diskless station

• RARP server keeps configuration table of mapping RARP server keeps configuration table of mapping

• RARP server is needed for each network because it RARP server is needed for each network because it

is reachable only by broadcast IP address (of all is reachable only by broadcast IP address (of all

ones)ones)

• BOOTPBOOTP (bootstrap protocol) provides same (bootstrap protocol) provides same

functionality by UDP (datagram) messages that functionality by UDP (datagram) messages that

travel over routers. Beside the local IP address it travel over routers. Beside the local IP address it

providesprovides

• IP address of the booting stationIP address of the booting station

• IP address of the default routerIP address of the default router

• the subnet maskthe subnet mask

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Dynamic Host Configuration Dynamic Host Configuration ProtocolProtocol

Operation of Operation of DHCPDHCP..

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The new IP version 6 (IPv6)The new IP version 6 (IPv6) Motivation:Motivation:

The threat of exhausting of the 32-bit IPv4 The threat of exhausting of the 32-bit IPv4 addess space. (addess space. (Original estimates for when Original estimates for when the world would run out of IPv4 numbers the world would run out of IPv4 numbers varied from 2000 to 2008.varied from 2000 to 2008.))

Fixing issues and problems in the existing Fixing issues and problems in the existing IPv4 implementationIPv4 implementation

Optimizing the network layer operationOptimizing the network layer operation

Introducing new network servicesIntroducing new network services

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IPv6 historyIPv6 history 19951995 - Experimental deployment - Experimental deployment

December, 1995December, 1995 - specifications of the basic - specifications of the basic protocols, RFC 1883protocols, RFC 1883

19961996 - more specifications - more specifications

19981998 - - RFC 2460RFC 2460 obsoletes RFC 1883. obsoletes RFC 1883.

2000-2000- Production quality support in all major OS Production quality support in all major OS and routers.and routers.

26.10.200726.10.2007- The - The RIPERIPE community issued a community issued a ‘Resolution on IPv4 Depletion and Deployment of ‘Resolution on IPv4 Depletion and Deployment of IPv6’IPv6’

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IPv6 Support RequirementsIPv6 Support Requirements

RoutersRouters must support IPv6 must support IPv6

SwitchesSwitches do not require upgrades to do not require upgrades to support support IPv6 UnicastIPv6 Unicast but will require but will require upgrades to support upgrades to support IPv6 Multicast IPv6 Multicast (MLDv2 snooping).(MLDv2 snooping).

DNSDNS management software must support management software must support IPv6.IPv6.

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IPv6 detailsIPv6 details IPv6 was designed to work together with IPv6 was designed to work together with

IPv4 (IPv4 (“Dual Stack”, “Dual Stack “Dual Stack”, “Dual Stack Strategy”Strategy”) )

During the transition period most hosts During the transition period most hosts will have both an IPv4 and an IPv6 will have both an IPv4 and an IPv6 number.number.

The transition period is expected to The transition period is expected to last last many years many years ((The wide use of The wide use of NATNAT will will slow down this proccessslow down this proccess).).

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IPv6 technicalIPv6 technical A A 128 bit128 bit address space address space

(about (about 3.4×103.4×103838 unique addresses comparing unique addresses comparing to to 4.3×104.3×1099 in IPv4 !!!) in IPv4 !!!)

The addresses are divided into 4 categories:The addresses are divided into 4 categories:– UnicastUnicast (corresponds to exactly one interface) (corresponds to exactly one interface)– MulticastMulticast (group address) (group address)– AnycastAnycast (corresponds to more than one interface) (corresponds to more than one interface)– Special addressesSpecial addresses

Examples Examples (IPv6 uses (IPv6 uses CIDRCIDR notation): notation):2001:4b58:acad::107/642001:4b58:acad::107/64 (a global unicast addr.)(a global unicast addr.)fe80::208:a1ff:fe7d:57df/64fe80::208:a1ff:fe7d:57df/64

(a link-local or autoconfiguration addr.)(a link-local or autoconfiguration addr.)::1/128::1/128 (the loopback address)(the loopback address)

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IPv6 technical (2)IPv6 technical (2) StatelessStateless autoconfiguration of hosts autoconfiguration of hosts

MulticastMulticast - part of the base specifications in IPv6, unlike IPv4, - part of the base specifications in IPv6, unlike IPv4, where it was introduced later.where it was introduced later.

Link-local addressesLink-local addresses

JumbogramsJumbograms – datagrams over the 64 KB IPv4 limit. – datagrams over the 64 KB IPv4 limit.

Network-layer securityNetwork-layer security - - IPsecIPsec is an integral part of the base is an integral part of the base protocol suite in IPv6.protocol suite in IPv6.

Mobility supportMobility support

Lack of a checksumLack of a checksum - It is believed that errors are very rare in - It is believed that errors are very rare in today's network. For this reason, IPv6 has no error checking in today's network. For this reason, IPv6 has no error checking in its protocol but instead relies on its protocol but instead relies on link layer protocolslink layer protocols to to perform error checking.perform error checking.

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IPv6 technical (3)IPv6 technical (3)IPv6 header formatIPv6 header format

Extension headers follow ...

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IPv6 - Transition IPv6 - Transition mechanisms mechanisms

Dual stackDual stack

TunnelingTunneling - Automatic or Configured - Automatic or Configured

Proxying and translationProxying and translation

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Barriers to implementing IPv6Barriers to implementing IPv6 The support in the wide used PC The support in the wide used PC

Operating systemsOperating systems– All three major OS (All three major OS (Linux, Mac OS X,Linux, Mac OS X, MS Windows MS Windows) have full support for IPv6 ) have full support for IPv6 now.now.

The support in the wide used routersThe support in the wide used routers–The major router vendors support IPv6The major router vendors support IPv6

IPv6 has been implemented more widelyIPv6 has been implemented more widelyin in EuropeEurope and and AsiaAsia than in the than in the USAUSA..

Some statistics next ...Some statistics next ...

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IANA IANA IPv6IPv6 Allocations to Allocations to RIRsRIRs

issued Oct 06issued Oct 06

RIRRIR IPv6 AddressIPv6 Address

AfriNICAfriNIC 2C00:0000::/12 2C00:0000::/12

APNICAPNIC 2400:0000::/12 2400:0000::/12

ARINARIN 2600:0000::/12 2600:0000::/12

LACNICLACNIC 2800:0000::/12 2800:0000::/12

RIPE NCCRIPE NCC 2A00:0000::/12 2A00:0000::/12

www.nro.net

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IPv6IPv6 Allocations AllocationsRIRs to LIRs/ISPsRIRs to LIRs/ISPs

(Mar 2009)(Mar 2009)www.nro.net

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IPv6IPv6 Allocations Allocations RIRs to LIRs/ISPsRIRs to LIRs/ISPs

Cumulative Total (Jan 1999 – Sep 2007)Cumulative Total (Jan 1999 – Sep 2007)

AfriNIC, 35, 2%

APNIC, 311, 22%

ARIN, 291, 20%

LACNIC, 104, 7%

RIPE NCC, 693, 49%

www.nro.net

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IPv6 in Bulgaria IPv6 in Bulgaria (May 2009)(May 2009)

source: http://www.sixxs.net

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IPv6 deployment in BREN’s IPv6 deployment in BREN’s networknetwork

(some pride ;-)(some pride ;-) The central node at The central node at IPP-BASIPP-BAS is fully IPv6 is fully IPv6

enabledenabled, including the NOC and part of , including the NOC and part of the LAN of IPP-BAS (the LAN of IPP-BAS (the most of the the most of the internal traffic is actually IPv6internal traffic is actually IPv6))

IPv6 traffic is also carried over four major IPv6 traffic is also carried over four major links in the BREN internal backbone:links in the BREN internal backbone:

• Sofia – Veliko TarnovoSofia – Veliko Tarnovo• Sofia – PlovdivSofia – Plovdiv• Sofia – PlevenSofia – Pleven• Sofia – VarnaSofia – Varna

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