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TCP/IP Protocol Suite
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Objectives
What is Internet?
Comparison of TCP/IP & OSI
Data Encapsulation
TCP-IP Protocol Suite
TCP/IP Protocol Documents
TCP-IP Protocol Suite (IPv4 vs IPv6)
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What is Internet?
Internet is network of networks, withdifferent hardware/software technologies
Also known by the name TCP/IP Internet
Name TCP/IP is taken from the names ofthe one of the transport layer protocols(Transport Control Protocol) and thenetwork layer protocol (Internet Protocol)
TCP/IP is backbone of the Internet
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TCP/IP and OSI
OSI is made of seven layers.
TCP/IP protocol is made of five layers.
PHYSICAL
DATA LINK
NETWORK
TRANSPORT
APPLICATION
PHYSICAL
DATA LINK
NETWORK
TRANSPORT
SESSION
PRESENTATION
APPLICATION
OSI Model TCP/IP Model
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Frame Head Trailer
Frame
Data Encapsulation
Data
Data
Data
TCP Header
TCP SegmentUDP Header
UDP Message
TCP-UDP DataIP Header
IP Datagram
IP Header TCP-UDP Data
Application
TPT Layer
NW Layer
Data Link
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D
P
N
T
A
TCP/IP Protocol Suite..
ICMP IGMPRARPARP
FTPSMTP
TELNETHTTP
TFTPNFS
SNMPDNS
TCP UDP
IP
Protocols defined bythe underlying networks
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Applications using TCP
File Transfer Protocol (FTP) Provides the ability to upload and download files
between hosts on the network.
Simple Mail Transport Protocol (SMTP)
Provides the ability to send mail between userson the network.
TELNET Provides the ability to login into a remote host
and administer the machine. Hyper Text Transfer Protocol (HTTP)
Provides the ability to supply web pages betweena browser and the server.
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Applications using UDP
Trivial File Transfer Protocol (TFTP) Provides simplex file transfer for network booting
of devices.
Network File System (NFS)
Provides the ability for sharing directoriesbetween hosts on the network.
Simple N/w Management Protocol (SNMP) Provides the ability to supply network
management services on the network. Domain Name Service (DNS)
Provides mapping between domain name and IPaddress and vice versa.
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TCP Details
Provides application programs access to thenetwork using a reliable connection-orientedtransport layer service
TCP sends and receives data reliably using
sequence numbers and acknowledgments TCP is a byte oriented protocol i.e. every
byte in each packet is assigned a sequencenumber
Data stream handed over to TCP is called anunstructured stream
TCP divides this data stream into segmentsfor transmission to remote network
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TCP Header..
76543210765432107654321076543210
ACKNOWLEDGEMENT NUMBER
DESTINATIONPORTSOURCEPORT
OPTIONS AND PADDING
URGENT POINTERCHECKSUM
WINDOW SIZEFIN
SYN
RST
PSH
ACK
URG
HELEN
Octet +3Octet +2
SEQUENCENUMBER
Octet +1Octet +0
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TCP Header
Source & Destination Port (16 Bits) Can run number of applications using same transport by
multiplexing through port numbers
Port numbers are used to identify a unique application in amachine
65536 (0-65535) port numbers can be defined
Theoretically it is possible to run 65535 simultaneousapplications in a host
The first 1024 ports, port numbers 0-1023 known as wellknown port numbers, are assigned and are reserved for
standard applications and are controlled by IANA
The remaining ports, 1024-65535, are dynamic and canbe used freely by applications
Source port is randomly generated by the source machine
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Well known port numbers
Network Time Protocol123
File Transfer-Data20
File Transfer-Control21
Telnet23
SMTP25
Domain Name Server53
Trivial File Transfer69
WWW80
DESCRIPTIONPORT
Border Gateway Protocol179
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TCP Header
Sequence Number (32 Bits) Helps in establishing TCP connections, along with SYN bit,
called as Three Way Handshake
Helps in maintaining account of amount of data beingtransferred
Identifies where the encapsulated data fits within a datastream from the sender
Sequence number is incremented, in the system, every 4microsecond
Acknowledgement Number (32 Bits)
Helps in maintaining account of amount of data beingtransferred
Identifies the sequence number expected from the otherend of data transmission unit
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Seq/Ack numbers relation
During TCP Connection Establishment/Three way handshake
Acknowledgement Number Sent = SequenceNumber Received+1
During Data Transfer Acknowledgement Number Sent = Sequence
Number Received + Data Received in Bytes
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Three-Way-Handshake
ReceiverSender 0 1
0-Closed; 1-Listen; 2-SYN-Sent; 3-SYN-Received; 4-Established
AN-00000
000B01
SN-95426
2
AN- 95427000B11
SN-16780 3
AN-16781
000B10
SN-95427
4
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Data Transfer
AN- 95428
100B10
SN-16781
5
AN- 95427
000B11
SN-16780AN-00000
000B01
SN-95426
AN-16781
000B10
SN-95427
ReceiverSender
0 1
0-Closed; 1-Listen; 2-SYN-Sent; 3-SYN-Received; 4-Established; 5-Data Transfer
23
4
AN-16881
200B10
SN-95428
5
AN- 95628
150B10
SN-16881
5
AN-17031
250B10
SN-95628
5
AN- 95878
300B10
SN-17031
5
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Closing a TCP Connection
ReceiverSender
6-Finish; 0- Closed
0 0
6
SN - 95880
AN -17334
0B110SN - 17334
AN - 95881
0B010
WAITSN - 17334
AN - 95881
0 B110
6
SN - 95881AN -17334
0B010
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TCP Header.
Header Length (4 Bits) Sometimes called Data Offset
Indicates the length of header in 32-bit words
Identifies the beginning of data
Typical value is 5 unless there are options Flags (6 Bits)
Urgent (URG)
Acknowledgement (ACK)
Push (PSH) Reset (RST)
Synchronisation (SYN)
Finish (FIN)
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TCP Header..
Window Size (16 Bits) Indicates the size of the sliding window
Specifies the number of octets, starting with theoctet indicated by the acknowledgement
number, that the sender of the segment willaccept from its peer at the other end of theconnection before the peer must stoptransmitting and wait for an acknowledgement
A default window size is 4096 bytes Used for flow control by using Sliding window
mechanism
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Flow Control
Sender retains a copy of transmitted data until itreceives an acknowledgment from the remotenetwork.
If no acknowledgment is received, within aspecified time, the data is retransmitted by using
adaptive retransmission algorithm. TCP records the time of the transmission and sequence
number of the segment.
TCP again records the time of the acknowledgementreceived.
Using this delta, TCP builds a sample round-trip delay timeand uses this to build an average time for a packet to besent and to receive an acknowledgement
TCP will time out after a number of unsuccessfulretransmissions
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Sliding Window-Flow Control
Moves to rightwhenack is received.
Moves to rightwhen
datais sent.
Moves to right or leftto fix
the size ofthe window.
Window Size
Sentand ack
Sent but notack
Can be sent
Cant be sent
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TCP Header..
Checksum(16 Bits) Used for error detection
Covers both header and the encapsulated data
Urgent Pointer(16 Bits) Used only when urgent flag is set Points to the last octet of urgent data
Options One of the important options is MSS (Maximum
Segment Size) Informs the receiver of the largest segment
the sender is willing to accept, withoutcausing fragmentation
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TCP Header
Padding Consists of 1-3 octets, each equal to zero, to
force the length of TCP header to be in multiplesof four octets.
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UserDatagram Protocol
Provides unreliable connectionless service Transfers data without establishing a
session
Used for services that have an inbuiltreliability
Does not use end to end error checking andcorrection
Does not order the packets; may loose orduplicate a packet
Runs faster than TCP due to less overheads
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UDP Header..
DESTINATIONPORTSOURCEPORT
CHECKSUMMESSAGE LENGTH
76543210765432107654321076543210
Octet +3Octet +2Octet +1Octet +0
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UDP Header...
Source Port (16 Bits) Identifies the sending process.
Destination Port (16 Bits)
Identifies the receiving process.
Some fixed, pre-assigned port numbers used for serviceson the Internet.
7 for UDP; 69 for TFTP
Message length (16 Bits)
Indicates the size of the UDP header and its data in bytes.
Minimum size is 8, if carries no data.
Checksum (16 Bits)
Covers the UDP header and UDP data.
Optional; If not used, set to all zeros.
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Internet Protocol.
Provides best-effort or connectionlessdelivery service.
No error checking or tracking
If reliability is important, IP must be paired
with a reliable protocol like TCP Transmits blocks of data called datagrams
each of which is transported separately
Responsible for IP addressing
Datagrams may travel along different routesand may arrive out of sequence orduplicated.
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IP Header..
HEADER CHECKSUMPROTOCOLTIME TO LIVE
DESTINATION ADDRESS OF HOST
SOURCE ADDRESS OF HOST
PADDINGOPTIONS
76543210765432107654321076543210
FRAGMENT OFFSETMFDFIDENTIFICATION
TOTAL LENGTHTOSHLENVER
Octet +3Octet +2Octet +1Octet +0
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IP Header
Version (4 Bits) Identifies the IP version to which the packet belongs
Header Length (4 Bits)
Indicates the length of IP header in 32 bit words.
Minimum length is 20 octets. Options may increase the size up to a maximum of 24
octets.
Type of Service (8 Bits)
Used for specifying special handling of packet.
Has two sub-fields:
Precedence
TOS
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IP Header.
0CRTDPPP
Reliability
0-Normal1-Maximise
Precedence
000-Routine001-Priority010-Immediate011-Flash100-Flash Override101-CRITIC/ECP110-Internetwork Control
111-Network Control
Delay
0-Normal1-Minimise
Throughput0-Normal
1-Maximise
Cost0-Normal
1-Minimise
Reserved:Always set to 0
0 = No TOS0000000
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IP Header..
Total Length (16 Bits) Specifies total length of the packet, including
header, in octets
Largest decimal number =216= 65535, themaximum possible size of an IP packet is 65535octets
Total length - header length = Packets datapayload
Identification (16 Bits) Each datagram is identified by a identification
number set by the source.
Normally incremented by 1 for each datagramsent.
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IP Header
Flags (3 Bits) First bit is not used.
Second bit is Dont Fragment (DF) bit
Third bit if More Fragment (MF) bit
Maximum Transmit Unit (MTU) is the size ofthe largest packet, including IP Header, thatcan be transmitted or received through adata link
Default MTU is 576 bytes, which can behandled by any network withoutfragmentation
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IP Header
Fragment Offset (13 Bits) The fragmentation occurs at the routers, if the
original packet length exceeds the MTU of a datalink
Used only in the cases when a datagram isfragmented on its way
Specifies the offset, in units of eight octets, fromthe beginning of header to the beginning of the
fragment Each fragment is marked, by router, with the
same identifier number
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Fragmentation..
172.16.2.0 172.16.3.0
MTU-1500 MTU-1500MTU-576
DataTCPIP
1500 B
DataTCPIP
512 B
Data
512 B
Data
476 B
DataTCPIP Data Data
DataTCPIP
IP IP IP
DF=0; MF=1; Offset=0 DF=0; MF=1; Offset=64 DF=0; MF=0; Offset=128
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Fragmentation
Only the receiver host reassembles thedatagram
The destination machine starts areassembly timer for about 60-120 seconds.
If not all fragments were received, thenhosts discard the packets and sends a timeexceeded ICMP message to the source
machine If a single fragment is lost during a
transmission, the entire packet must beresent
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IP Header
Time to live-TTL (8 Bits) Assigns a life to an IP datagram
Protocol (8 Bits)
Specifies the protocol that runs on the top of IP.
TCP-6; EGP-8; UDP-17; OSPF-89
Header Checksum (16 Bits)
Error detection field for IP header
As each router decrements the TTL, thechecksum is calculated by each router
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IP Header.
Source Address of Host (32 Bits) IP Address of the Originating Machine
Destination Address of Host (32 Bits)
IP Address of the Destination Machine
Options Security:
Specifies how secret the datagram is Strict Source Routing(SSR):
Gives the complete path to be followed Loose Source Routing(LSR):
Gives the list of routers not to be missed
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IP Header..
Record Route: Makes each router to append its IP address.
Time Stamp: Makes each router to append its IP address
and time stamp.
Padding
Ensures that the header ends on a 32 bitboundary by adding zeros after the option field.
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Underlying Networks Protocols
Ethernet Token Ring
FDDI Fiber Distributed Data Interface
HDLC High-level Data Link Control
Frame Relay
PPP Point-to-Point Protocol
ATM Asynchronous Transfer Mode
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Socket Connection..
Ports along with an IP address, known assocket connection, allow any application inany machine on an internet to be uniquelydefined.
Multiple applications can run simultaneouslyon a host by making use of separate socketconnection for each application.
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Socket Connection-Multiplexing
DATA
DATA
3753-53
2764-21
DATA
DATA
DATA 3753-53
2764-21DATA
A.B.C.D-E.F.G.H
A.B.C.D-E.F.G.H
A.B.C.D-E.F.G.HDATA 3753-53
2764-21DATA A.B.C.D-E.F.G.H
TRAILER
TRAILER HEADER
HEADER
D
P
N
T
DNSFTP
2764 3753
TCP UDP
IP
A.B.C.D
DNSFTP
21 53
TCP UDP
E.F.G.H
1. A.B.C.D(2764) E.F.G.H(21) 2. A.B.C.D(3753) E.F.G.H(53)
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Socket Connection-Demultiplexing
DP
N
T
DNSFTP
2764 3753
TCP UDP
IP
A.B.C.D
DNSFTP
21 53
TCP UDP
E.F.G.H
53- 3753
21- 2764
DATA
DATA
DATA 53- 3753
21- 2764DATA
E.F.G.H-A.B.C.D
E.F.G.H-A.B.C.D
DATA
DATA
E.F.G.H-A.B.C.DDATA 53- 3753
21- 2764DATA E.F.G.H-A.B.C.D
TRAILER
TRAILER HEADER
HEADER
1. A.B.C.D(2764) E.F.G.H(21) 2. A.B.C.D(3753) E.F.G.H(53)
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Internet Control Message Protocol
Internet Control Message Protocol is amechanism used by hosts and routers tosend notification of datagram problems backto the sender.
Sends error messages only to the sourceand not to intermediate routers.
Sole function is to report problems, not tocorrect them.
An important use of ICMP is echo/reply totest whether a destination is reachable andresponding.
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Internet Control Message Protocol
Echo request/reply (PING; Packet INternetGropher)
Destination unreachable
0-Network unreachable
1-Host unreachable
2-Protocol unreachable
3-Port unreachable
4-Fragment needed but DF bit is set
5-Source route failed
6-Destination network unknown
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Internet Control Message Protocol
7-Destination host unknown 8-Source host isolated
9-Communication with destination networkadministratively prohibited
10-Communication with destination hostadministratively prohibited
11-Network unreachable for type of service
12-Host unreachable for type of service
Time exceeded message format 0-TTL exceeded
1-Fragment reassembly time exceeded
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Internet Group Message Protocol
Internet Group Message Protocol providesallows for multicast to operate on aninternetwork.
Multicast is one-to-many communication.
A message sent can be simultaneously receivedby a group of hosts.
Special type of Class-D IP addresses,starting with 1110, are reserved as
multicast addresses.
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Address Resolution Protocol
Address Resolution Protocol is used totranslate 32 bits IP addresses to 48 bitsEthernet addresses.
A hosts physical address is determined by
broadcasting its IP address to all machines.
The machine with matching IP address, inbroadcast message, sends its hardwareaddress to the machine originatingbroadcast.
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ARP Operation
Request
Ignored
Request
IgnoredARP
Response
Accepted
Give me MAC address of129.1.1.4
Thats
Me
Here is my MAC address
129.1.1.1 129.1.1.4
129.1.1.2 129.1.1.3
08-00-39-00-2F-C3
08-00-10-99-AC-54
08-00-5A-21-A7-2208-00-39-00-2F-AB
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Reverse Address Resolution Protocol
Reverse Address Resolution Protocol isused to get the 32 bits Source IPaddress, knowing the 48 bits Hardwareaddress.
It is reverse of ARP, hence namedReverse Address Resolution Protocol.
A diskless workstation broadcasts RARP-
Request to find its IP Address at the timeof boot up.
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RARP Operation
Give me my IP address RARP Response
Diskless
work
station RARP
Server
08-00-39-00-2F-C3 08-00-10-99-AC-54
08-00-5A-21-A7-22
223.1.2.1
223.1.2.2
223.1.2.3
08-00-39-00-2F-AB
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IPv4 vs IPv6
Some independent protocols of version 4are part of ICMPv6.
RARP protocol is dropped from the suite.
ARP and IGMP are combined with ICMPv6.
ICMP IGMP
RARPARPIPv4
ICMPIPv6
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IPv6 Base Header
DESTINATION ADDRESS
(128 Bits)
SOURCE ADDRESS(128 Bits)
PAYLOAD (0-65535 Bytes)
(EXTENSIONHEADERS + DATA PACKETS FROMUPPERLAYERS)
HOP LIMITNEXT HEADERPAYLOAD LENGTH
FLOW LABELPRIVER
76543210765432107654321076543210
Octet +3Octet +2Octet +1Octet +0
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TCP/IP Protocol Documents
TCP/IP technical documents are known asRequest For Comments (RFCs).
Once issued, RFC do not change.
Updated by new RFCs.
RFCs can be obsoleted but their numbers arenever used again.
A major source for RFCs is the InternetEngineering Task Force and are accessibleon site www.ietf.org
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