Telecommunications Concepts

1
TelecommunicationsConcepts

• Chapter 4.1
• The Integration
• TCP/IP

2
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

3
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

4
The Internet Transport Layer
Transport Layer
Internet Layer
Networks Layer
5
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.

6
The Internet SublayerDesign 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

7
The Internet Sublayer OSI approach
Application 1
Application 2
Application 3
TP0-4
Internet Sublayer
Enh
Enh
Enh
any network
8
The Internet SublayerIP approach
Application 1
Application 2
Application 3
TCP
UDP
Internet Protocol
any network
9
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

10
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

11
IP Networks
ISDN/PSTN Leased Line
LAN
Router
WAN
12
Unicast
Unicast, Multicast and Broadcast
Multicast
Broadcast
13
Multipoint Unicasting
14
Multicasting
15
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

16
IP v4 addresses

• Four different address formats

Class D
1110
Predefined Multicast groups(28)

• Net/Host all 0s Unknown address
• Net/Host all 1s Broadcast

17
IP v4 addressesSome Examples
MIT... INFOS1 WWW.IEEE
xxxxxxxx xxx. 10111000 184. 10101100 172.
00010010 18. 10000110 134. 11000111 199.
xxxxxxxx xxx. 00000001 1. 10001000 136.
xxxxxxxx xxx 01111101 125 00000001 1
18
Routing in large networks

• Complete routing tables impossible in large
  networks
• Hierarchical routing is the solution
• Routing table restricted to one level of
  hierarchy

19
IP v4 Subnetting(example on Class C network
195.1.1)
1
Network number
Subnet
1
0
Host
21 bits
3 bits
5 bits

• 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 address 32
(001) 195.1.1.33 - 195.1.1.62
195.1.1.63 64 (010) 195.1.1.65 - 195.1.1.94
195.1.1.95 96 (011) 195.1.1.97 - 195.1.1.126
195.1.1.127
20
IP v4 Subnetting ( Example the 195.1.1.0 / 27
Network)
To the Internet (Network 195.1.1.00)
195.1.1.33/27
195.1.1.34/27
195.1.1.65/27
195.1.1.66/27
A
D
C
B
195.1.1.98/27
195.1.1.97/27
Remark In the notation xxx.xxx.xxx.xxx / n n
gives the number of 1s in the mask
F
E
21
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

22
IP v4 datagram format
IP header
IP Data Area
Total Length
Typ.Ser.
Ver
Len
Fl.
Ident
Frag.Offset
TTL
Proto
23
IP v4 Header (1)
Total Length
Typ.Ser.
Ver
Len
Ident
Frag.Offset
Fl.
Header Checksum
TTL
Proto
Source IP Address
Destination IP Address
Options
Padding
Ver Protocol version, incompatible
datagrams are rejected. Len Length of header,
in 32 bit words. Tot.Length Length, in bytes, of
the entire datagram.
24
IP v4 Header (2)
Total Length
Typ.Ser.
Ver
Len
Ident
Frag.Offset
Fl.
TTL
Proto
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)
25
IP datagram fragmentation
- Packet size exceeds maximum size in network -
Excessive delay jitter due to long packets
26
IP v4 Header (3)
Total Length
Typ.Ser.
Ver
Len
Ident
Frag.Offset
Fl.
TTL
Proto
Ident Unique identifier of fragmented
datagram. Fl Do not fragment bit. More
fragments bit. Frag.Offset Offset of segment in
original datagram.
27
IP v4 Header (4)
Total Length
Typ.Ser.
Ver
Len
Ident
Frag.Offset
Fl.
Header Checksum
TTL
Proto
Source IP Address
Destination IP Address
Options
Padding
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.
28
IP v4 Header (5)
Total Length
Typ.Ser.
Ver
Len
Ident
Frag.Offset
Fl.
Header Checksum
TTL
Proto
Source IP Address
Destination IP Address
Options(var. length)
Padding
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
29
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 2
• Option
• 4 Internet timestamp var

30
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

31
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

32
IP Networks
Router
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
7.1
2.3
6.2
33
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 )

34
IP Networks
1.2 gt 7.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 1.1
1 1
7.1
6.2
35
IP Networks
1.2 gt 7.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 3.2 2.2
1,2,3 4 gt4
7.1
6.2
36
IP Networks
1.2 gt 7.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 2.1 5.3
2,5,6 1,3,4 7
7.1
6.2
37
IP Networks
1.2 gt 7.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 5.2 5.1
5,7 1,3,4 2,6
7.1
6.2
38
IP Networks
7.2 gt 1.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 7.1
7 7
7.1
6.2
39
IP Networks
7.2 gt 1.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 5.2 5.1
5,7 1,3,4 2,6
7.1
6.2
40
IP Networks
7.2 gt 1.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 3.3 5.1
3,4,5 1,2 6,7
7.1
6.2
41
IP Networks
7.2 gt 1.2
4.2
4.1
1.2
3.2
4.3
1.1
3.3
1.3
5.2
2.1
1.4
5.1
2.2
5.3
6.1
7.2
direct 3.2 2.2
1,2,3 4 gt4
7.1
6.2
42
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

43
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 !

44
Classless InterDomain Routing
MIT... INFOS1 WWW.IEEE Belnet
xxxxxxxx xxx. 10111000 184. 10101100 172. 10111110
190.
00010010 18. 10000110 134. 11000111 199. 11000001
193.
xxxxxxxx xxx. 00000001 1. 10001000 136. xxxxxxxx
xxx.
xxxxxxxx xxx 01111101 125 00000001 1 xxxxxxxx xxx
45
Classless InterDomain Routing

• 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

46
Classless InterDomain Routing

• 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

47
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

48
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

49
ICMP error messages
Error causing IP packet
IP header
IP Data Area
Tr. header
Transport data area
IP header
Tr. header
IP header
ICMP error message
Error reporting ICMP packet
50
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

51
The Internet Transport Layer
Applications Layer
Transport Layer
Internet Layer
Networks Layer
52
The Transport Layeris an end to end service
Host B
Host A
Appl.
Appl.
Transp.
Transp.


Netw.
Netw.



53
QOS and the Transport Layer
Connection Oriented / Connectionless Transport
Service with specified Quality of Service
Transport Layer
Connection Oriented / Connectionless Network
Service with Quality of Service imposed by
technology
54
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

55
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
• gtgt No guaranteed delays
• Service required from network layer
• Connectionless network service
• (As provided by the Internet Protocol)

56
TCP segment format
TCP header
TCP Data Area
Source Port
Destination Port
Sequence Number
Acknowledgment Number
Window Size
Off. Res. Code
Checksum
Urgent Pointer
padding
Options
57
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

58
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

59
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)

60
UDP message format
UDP header
UDP Data Area
UDP header 8 bytes

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

61
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)

62
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

63
Network Address Translation
intranet
Internet
192.168.1.10
134.184.23.112
NAT
192.168.1.11
192.168.1.12
TCP and UDP port numbers are abused to identify
the hosts on the intranet.
64
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

65
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

66
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

67
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

68
IP v4 datagram format
IP header
IP Data Area
Total Length
Typ.Ser.
Ver
Len
Fl.
Ident
Frag.Offset
TTL
Proto
69
IP v6 Header (1)
Flow Label
Ver
Pri
Payload Length
Next Hdr
Hop Lim.
Source IP Address
Destination IP Address
70
IP v6 Addresses
128 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 21DAD302F3B2AAFFFE289C5A
71
IP v6 Unicast Addresses
Hierarchical addresses to facilitate routing.
TLA Top level aggregation identifier (global
ISPs) NLA Next level aggregation identifier
(within ISP) res reserve bits to be added to TLA
or NLA in future SLA Site level aggregation
identifier (local subnet) INT Interface
identifier on a specific subnet (equivalent to
v4 host identifier, but now, a single computer
can have several interfaces)
72
Unicast
Anycast Addresses
Anycast
73
IP v6 Header (2)
Flow Label
Ver
Pri
Payload Length
Next Hdr
Hop Lim.
Source IP Address
Destination IP Address
Priority a step towards QOS control
Flow controlled traffic (TCP) 0 - 7 1 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
- 15 Real time video and audio, ...
74
IP v6 Header (3)
Flow Label
Ver
Pri
Payload Length
Next Hdr
Hop Lim.
Source IP Address
Destination IP Address
Flow Label an other step towards QOS control
Flow connection oriented communication implement
ed through connectionless service Flow uniquely
identified by source address flow label Future
routers could reserve resources for flows
75
BibliographyTo know More about IPng

• Scott 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

76
Further Readings on the INTERNET
By Douglas E. COMER Published by Prentice Hall
International Editions

• 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