J.Tiberghien - VUB12-06-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 4.1...

J.Tiberghien - VUB12-06-K.Steenhaut & J.Tiberghien - VUB1

TelecommunicationsConcepts

Chapter 4.1

The Integration :

TCP/IP


Contents

• The internet concept• Version 4 Internet Protocols

– IP addressing– IP headers– CIDR– ICMP

• The transport layer– The Transmission Control Protocol– The User Datagram Protocol

• Network Address Translation• Version 6 Internet Protocol• Side track : IP routing


Contents






The Internet & Transport Layer

Applications Layer

Internet Layer

Transport Layer

Networks Layer


The Internet Sublayer

• Modern data communications require connectivity through many different networks

• Existing networks offer diverse

– services levels (Connectionless/Connection Oriented)

– interfaces with transport layer

• An Interface layer (the INTERNET layer) is added on top of the Network layers

• The INTERNET layer ensures

– Uniform addressing through all networks

– Well defined and identical services from all networks

– A common interface with the Transport layer.



Design Philosophy• In the OSI Community : Less performing networks are enhanced

– Additional sublayer between network and internet layers : The Enhancement Sublayer.

– Most often, Connection oriented, Reliable.– Inspired by X25

• In the Internet Community (Internet Protocol): Minimal Internet Service definition

– Service restricted to whatever all networks can do : Connectionless, Unreliable– Inspired by Local Area Networks



OSI approachApplication 1 Application 2 Application 3

TP0-4

Internet Sublayeran

yn

etw

ork

Enh Enh Enh



IP approachApplication 1 Application 2 Application 3

TCP

Internet Protocolan

yn

etw

ork

UDP


Original IP Services

• Internet-wide uniform addressing.

– Two part addresses

» Network : identifies the network

» Host : identifies host on a specific network.

( Host part = subnet identifier + host identifier )

• Connectionless, unreliable datagram service

• Fragmentation when required by network

• Routing through the entire Internet.

• Elimination of “lost” datagrams

• Debugging facilities

• Special transmission modes


Contents






IP Networks

ISDN/PSTNLeased LineRouter LAN

WAN


Unicast

Unicast, Multicast and Broadcast

Multicast

Broadcast


Multipoint Unicasting


Multicasting


Internet multicasting

• Distribute information to a group of selected users without overly taxing a networks’ resources

• Deliver ONE COPY of a datagram to all subnetworks to which group members are attached

• Definition of Multicast host group–Class D multicast addresses

• A mechanism to JOIN and LEAVE a multicast group– sender or receiver based control of group

membership–protocols to transmit and manage the group

membership info throughout the network


IP v4 addresses

Net/Host = all 0’s : Unknown address

Net/Host = all 1’s : Broadcast

0 Net (7) Host (24)Class A :

126 networks with up to 16 million hosts each

Four different address formats

10 Net (14) Host (16)Class B :

16382 networks with up to 65534 hosts each

110 Net (21) Host (8)Class C :

2 million networks with up to 254 hosts each

1110 Predefined Multicast groups(28)Class D :


IP v4 addresses

Some Examples0 Net (7) Host (24)Class A :



MIT... :

INFOS1 :

WWW.IEEE

xxxxxxxxxxx.10111000184.10101100172.

0001001018. 10000110134.11000111199.

xxxxxxxxxxx. 000000011.10001000136.

xxxxxxxxxxx 01111101125000000011


Routing in large networks

• Complete routing tables impossible in large networks

• Hierarchical routing is the solution

– Routing table restricted to one level of hierarchy


IP v4 Subnetting(example on Class C network 195.1.1)

• Host number can be split : Subnet + Host

• Length of actual host number given by mask

• MASK 11111111 11111111 11111111 11100000

• MASK 255 . 255 . 255 . 224

• Each subnet in example : 30 hosts (32 - 2)

Subnet number Addresses Broadcast address32 (001) 195.1.1.33 - 195.1.1.62 195.1.1.6364 (010) 195.1.1.65 - 195.1.1.94 195.1.1.9596 (011) 195.1.1.97 - 195.1.1.126 195.1.1.127

1 Network number Subnet1 0 Host

21 bits 3 bits 5 bits


IP v4 Subnetting ( Example : the 195.1.1.0 / 27 Network)

E F

CA B195.1.1.33/27 195.1.1.34/27 195.1.1.65/27

D195.1.1.66/27

195.1.1.97/27 195.1.1.98/27

To the Internet (Network 195.1.1.00)

Broadcast: 195.1.1.95Subnet : 195.1.1.64



Remark :In the notationxxx.xxx.xxx.xxx / nn gives the number of 1’s in the mask


Contents






IP v4 datagram format

IP header IP Data Area

Source IP Address

Destination IP Address

Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len


IP v4 Header (1)

Source IP Address


Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

Ver : Protocol version, incompatible datagrams are rejected.

Len: Length of header, in 32 bit words.Tot.Length: Length, in bytes, of the entire datagram.


IP v4 Header (2)

Source IP Address


Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

Typ.Serv.: Precedence (0 = normal, 7 = control)D = Short delay wanted (best effort)T = High throughput wanted (best effort)R = High reliability wanted (best effort)


IP datagram fragmentation

IP header Fragment 2IP header Fragment 1


- Packet size exceeds maximum size in network- Excessive delay jitter due to long packets


IP v4 Header (3)

Source IP Address


Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

Ident : Unique identifier of fragmented datagram.Fl: “Do not fragment” bit.

“More fragments” bit.Frag.Offset: Offset of segment in original datagram.


IP v4 Header (4)

Source IP Address


Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

TTL : Time To Live (decremented at each node) Datagram discarded when TTL = 0.

Proto: Identifies the higher layer protocols.HdrCks: Redundant error detection bits for header.


IP v4 Header (5)

Source IP Address


Options(var. length) Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

Options : Debuging and special transmission modes copy : Option field reproduced in all fragments class : 0 = datagram or network control

2 = debuging and measurement number : specifies the function of the option


IP v4 Options

Class 0 Length

Option

– 1 : End of option list 1

– 2 : Security and handling restrictions 11

– 3 : Loose Source Routing var

– 7 : Record route var

– 9 : Strict Source Routing var

Class 2Option

– 4 : Internet timestamp var


Contents






Routing• Routing = transmission of a datagram

– from a “source IP address”

– to a “destination IP address”

• Direct Routing

– Current and destination addresses on same network

– Direct delivery to destination

• Indirect Routing

– Current and destination addresses on different networks

– Datagram forwarded from source to destination via routers

– Routers have an address in at least two networks


IP Networks

Router1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

2.3

6.1

6.2

5.35.1

7.17.2


Routing

IF destination net is directly connected

THEN (* Direct Routing *)

encapsulate datagram in network frame;

send frame to destination;

ELSE (* Indirect Routing *)

with “destination net” as index in local routing table, find address of local router appropriate for reaching that net;

encapsulate datagram in network frame;

send frame to selected local router;

END (* IF *)


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

1.2 > 7.2

2.3

Dest.net Forw.to

direct1.1

1#1


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

2.3

Dest.net Forw.to

direct3.22.2

1,2,34

>4

1.2 > 7.2


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

1.2 > 7.2

2.3

Dest.net Forw.to

direct2.15.3

2,5,61,3,4

7


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

1.2 > 7.2

2.3

Dest.net Forw.to

direct5.25.1

5,71,3,42,6


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

7.2 > 1.2

2.3

Dest.net Forw.to

direct7.1

7#7


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

7.2 > 1.2

2.3

Dest.net Forw.to

direct5.25.1

5,71,3,42,6


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

7.2 > 1.2

2.3

Dest.net Forw.to

direct3.35.1

3,4,51,26,7


IP Networks

1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

6.1

6.2

5.35.1

7.17.2

7.2 > 1.2

2.3

Dest.net Forw.to

direct3.22.2

1,2,34

>4


Contents






Classless InterDomain Routing

• Problems with class based addressing : – Too few Class B networks. – Class C networks too small

• Obvious solution :– Multiple Class C addresses for single network

• But…– All routers should know all networks

– Over 10 6 class C networks possible !









MIT... :

INFOS1 :

WWW.IEEE

Belnet

xxxxxxxxxxx.10111000184.10101100172.10111110190.

0001001018. 10000110134.11000111199.11000001193.

xxxxxxxxxxx. 000000011.10001000136.xxxxxxxxxxx.

xxxxxxxxxxx 01111101125000000011xxxxxxxxxxx



Techniques to limit size of router tables:

• Replace classes by variable sized networks :

– associate with each network number a mask.

– mask defines network size.

– Router tables contain network number & mask

• Assign new addresses on a geographical basis :

– Europe : 194.0.0.0 to 195.255.255.255

– N.America : 198.0.0.0 to 199.255.255.255

– S.& C.America : 200.0.0.0 to 201.255.255.255

– Asia : 202.0.0.0 to 203.255.255.255



Examples of address assignment: • User X : 2048 addresses, 194.24.0.0 to 194.24.7.255

– Addr = 11000010 00011000 00000XXX XXXXXXXX– Mask = 11111111 11111111 11111000 00000000

• User Y : 4096 addresses, 194.24.16.0 to 194.24.31.255– Addr = 11000010 00011000 0001XXXX XXXXXXXX– Mask = 11111111 11111111 11110000 00000000

• User Z : 1024 addresses, 194.24.8.0 to 194.24.11.255– Addr = 11000010 00011000 000010XX XXXXXXXX– Mask = 11111111 11111111 11111100 00000000

• Unknown address : 194.24.17.4– X : 11000010 00011000 00010001 00000100– y : 11000010 00011000 00010001 00000100– z : 11000010 00011000 00010001 00000100


Contents






Internet Control Message Protocol

Specific messages exchanged by routers to

– Report errors

» Destination unreachable

» Time to live exceeded

» Invalid header field

» …

– Explore and reconfigure network

» Request echo / Answer echo request

» Request timestamp / Answer timestamp request

» Redirect routes

» …


ICMP error messages

Tr. header Transport data area

IP header ICMP error message


Error causing IP packet

Error reporting ICMP packet

IP header Tr. header


Contents






The Internet & Transport Layer

Applications Layer

Internet Layer

Transport Layer

Networks Layer


The Transport Layer

is an end to end service

Appl. Appl.

Transp. Transp.

Netw. Netw.

Host A Host B


QOS and the Transport Layer

Transport Layer

Connection Oriented / Connectionless Transport Servicewith specified Quality of Service

Connection Oriented / Connectionless Network Servicewith Quality of Service imposed by technology


Contents






Transport Control Protocol

• Service offered to application layer :– Application port identification– Stream of bytes is transferred between applications– Connection oriented full-duplex communication– Data-stream decomposed in sequence of data

segments– Error correction with sliding window algorithm– Best effort congestion control >> No guaranteed delays

• Service required from network layer :– Connectionless network service (As provided by the Internet Protocol)


TCP segment format

TCP header TCP Data Area

Source Port Destination Port

Window Size

Checksum

Sequence Number

Acknowledgment Number

Urgent Pointer

Off. | Res. | Code

paddingOptions


TCP Error Correction• Sliding window error correction

• Cumulative Acknowledgment– Position in stream of last received byte– Acknowledgments piggybacking with reverse traffic– Retransmission policy implementation dependent

• Adaptive time-out– Network delays vary widely due to traffic fluctuations– Round-trip time continuously monitored– Time-out based on weighted average of round-trip times

• Congestion control– Receiver congestion prevented by adapting window size – Network congestion detected by round-trip delay analysis– Congestion cured by slowing down transmissions


Contents






User Datagram Protocol

• Service offered to application layer :–Application port identification

–Connectionless (stateless)

–Error detection, no correction

• Service required from network layer :–Connectionless network service

(As provided by the Internet Protocol)


UDP message format

UDP header UDP Data Area

Source Port Destination Port

UDP ChecksumLength

• Destination Port : Application identifier• Source Port : 0 or port for answering• Length : in bytes, inclusive the header 0 <= DataLength <= 65,527 bytes• Checksum : Redundant bits for error detection

UDP header : 8 bytes


UDP Port Numbers(some examples)

• 0 Reserved

• 7 Echo

• 11 Users (Gives list of active users)

• 13 Daytime

• 17 Quote (Gives the quote of the day)

• 53 Domain (Domain name server)

• 67 BOOTPS (Bootstrap Protocol Server)

• 68 BOOTPC (Bootstrap Protocol Client)

• 69 TFTP (Trivial File Transfer Protocol)

• 123 NTP (Network Time Protocol)


Contents






Network Address Translation

Internet

192.168.1.10

192.168.1.11

192.168.1.12

NAT

134.184.23.112

intranet

TCP and UDP port numbers are abused to

identify the hosts on the intranet.


Network Address Translation

• Work-around for solving IPv4 address shortage.• Maps many intranet addresses into a single internet

address.• Uses TCP or UDP non standard port numbers to identify

hosts in the intranet.• A NAT device can not be stateless and therefore is a

reliability threat.• NAT devices are not transparent to transport protocols

different from TCP or UDP.• NAT devices jeopardize peer to peer applications • Is believed by some to increase intranet security• Is a good excuse for further delaying IPv6 deployment


Contents






IP Next

Generation• Reasons to change IP

– Insufficient address space.

– No effective QOS guarantees

– No practical support for secure communications

– No good support for multicasting

• Constraints on any successor to IP– Upward compatibility with IPv4

– Not significantly less efficient than IPv4


IP ng = IPV6

• 2128 instead of 232 possible addresses

– Upward compatible with IP v4 addresses

– New “anycast” addressing mode

– Provisions for more efficient multicasting

– Provisions for addresses of other protocols

• Provisions for QOS specification

• More efficient header format

– Little used fields removed

– Options handled through extension header

• Security

– Authentication

– Data integrity

– Confidentiality


IP v4 datagram format


Source IP Address


Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len


IP v6 Header (1)

Source IP Address


Payload Length

Flow Label

Next Hdr Hop Lim.

Ver Pri


IP v6 Addresses128 bit addresses = 7. 1023 addresses / m2 on the earth !

Prefix Allocation Fraction

0000 001 NSAP 1/128 (0.8%)0000 010 IPX 1/128 (0.8%)001 Global unicast 1/8 (12.5%)010 Provider unicast 1/8 (12.5%)100 Geographic unicast 1/8 (12.5%)1111 1110 1 Local use addresses 1/512 (0.2%)1111 1111 Multicast groups 1/256 (0.4%)

Represented as 8 groups of 4 hex digits, separated by colons, leading zeros suppressed:

21DA:D3:0:2F3B:2AA:FF:FE28:9C5A


IP v6 Unicast AddressesHierarchical addresses to facilitate routing.

001 INTresTLA SLANLA

3 13 8 24 18 64

TLA: Top level aggregation identifier (global ISP’s)NLA: Next level aggregation identifier (within ISP)res: reserve bits to be added to TLA or NLA in futureSLA: Site level aggregation identifier (local subnet)INT: Interface identifier on a specific subnet

(equivalent to v4 host identifier, but now, a singlecomputer can have several interfaces)


Unicast Anycast

Anycast Addresses


IP v6 Header (2)

Source IP Address


Payload Length

Flow Label

Next Hdr Hop Lim.

Ver Pri

Flow controlled traffic (TCP) : 0 - 71 = filler traffic (NetNews, ...)4 = attended bulk transfer (FTP, HTTP, ...)6 = Interactive traffic (Telnet, X, ...)7 = Internet control traffic (routing, SNMP, ...)

Traffic without flow control (UDP) : 8 - 15Real time video and audio, ...

Priority : a step towards QOS control


IP v6 Header (3)

Source IP Address


Payload Length

Flow Label

Next Hdr Hop Lim.

Ver Pri

Flow = connection oriented communicationimplemented through connectionless service

Flow uniquely identified bysource addressflow label

Future routers could reserve resources for flows

Flow Label : an other step towards QOS control


BibliographyTo know More about

IPngScott o. Bradner, Allison Mankin

IPng

Internet Protocol Next Generation

Addison-Wesley Publishing Company,1996.

ISBN 0-201-63395-7 Available in the VUB Library :

ESP

681.30

G

BRAD

96


Further Readings on the INTERNET

– The INTERNET Book, 4th edition 2007. Everything you need to know about computer networking and how the

Internet works ISBN 0-13-233553-0– Internetworking with TCP/IP, Volume I, 5th edition, 2006. Principles, Protocols and Architecture ISBN 0-13-187671-6– Internetworking with TCP/IP, Volume II, 3rd edition, 1999. Design, Implementation, and Internals (with D.Stevens) ISBN 0-13-973843-6– Internetworking with TCP/IP, Volume III, 2000. Client-Server Programming and Applications,

Linux/POSIX Socket Version (with D.Stevens) ISBN 0-13-032071-4

By Douglas E. COMERPublished by Prentice Hall International Editions

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