Transcript Chap41-TCPIP

Telecommunications
Concepts
Chapter 4.1
The Integration :
TCP/IP
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12-06-K.Steenhaut & J.Tiberghien - VUB
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
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12-06-K.Steenhaut & J.Tiberghien - VUB
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
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The Internet & Transport Layer
Applications Layer
Transport Layer
Internet Layer
Networks Layer
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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.
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The Internet Sublayer
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
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The Internet Sublayer
OSI approach
Application 1
Application 2
Application 3
TP0-4
Internet Sublayer
Enh
Enh
any
network
Enh
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The Internet Sublayer
IP approach
Application 1
Application 2
TCP
Application 3
UDP
any
network
Internet Protocol
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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
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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
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IP Networks
Router
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LAN
WAN
ISDN/PSTN
Leased Line
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Unicast, Multicast and Broadcast
Unicast
Multicast
Broadcast
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Multipoint Unicasting
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Multicasting
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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
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IP v4 addresses
Four different address formats
Class A :
0
Net (7)
Host (24)
126 networks with up to 16 million hosts each
Class B :
10
Net (14)
Host (16)
16382 networks with up to 65534 hosts each
Class C :
110
Net (21)
Host (8)
2 million networks with up to 254 hosts each
Class D :
1110
Predefined Multicast groups(28)
Net/Host = all 0’s : Unknown address
Net/Host = all 1’s : Broadcast
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IP v4 addresses
Some Examples
Class A :
0
Class B :
10
Class C :
110
MIT... :
INFOS1 :
WWW.IEEE
17
Net (7)
00010010
18.
10000110
134.
11000111
199.
Host (24)
Net (14)
Host (16)
Net (21)
xxxxxxxx
xxx.
10111000
184.
10101100
172.
Host (8)
xxxxxxxx
xxx.
00000001
1.
10001000
136.
xxxxxxxx
xxx
01111101
125
00000001
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Routing in large networks
• Complete routing tables impossible in large networks
• Hierarchical routing is the solution
– Routing table restricted to one level of hierarchy
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IP v4 Subnetting
(example on Class C network 195.1.1)
1 1 0
Network number
21 bits
•
•
•
•
•
3 bits
Host
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
32 (001)
64 (010)
96 (011)
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Subnet
Addresses
Broadcast address
195.1.1.33 - 195.1.1.62
195.1.1.63
195.1.1.65 - 195.1.1.94
195.1.1.95
195.1.1.97 - 195.1.1.126 195.1.1.127
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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
A
B
Subnet
: 195.1.1.32
Broadcast: 195.1.1.63
Remark :
In the notation
xxx.xxx.xxx.xxx / n
n gives the number of
1’s in the mask
20
195.1.1.65/27
C
195.1.1.66/27
D
Subnet
: 195.1.1.64
Broadcast: 195.1.1.95
195.1.1.97/27
E
195.1.1.98/27
F
Subnet
: 195.1.1.96
Broadcast: 195.1.1.127
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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
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IP v4 datagram format
IP header
IP Data Area
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
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IP v4 Header (1)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
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.
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IP v4 Header (2)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
Typ.Serv.:
24
Precedence (0 = normal, 7 = control)
D = Short delay wanted (best effort)
T = High throughput wanted (best effort)
R = High reliability wanted (best effort)
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IP datagram fragmentation
IP header
IP header
Fragment 1
IP Data Area
IP header
Fragment 2
- Packet size exceeds maximum size in network
- Excessive delay jitter due to long packets
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IP v4 Header (3)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
Ident :Unique identifier of fragmented datagram.
Fl:
“Do not fragment” bit.
“More fragments” bit.
Frag.Offset: Offset of segment in original datagram.
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IP v4 Header (4)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
TTL :
Proto:
HdrCks:
27
Time To Live (decremented at each node)
Datagram discarded when TTL = 0.
Identifies the higher layer protocols.
Redundant error detection bits for header.
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IP v4 Header (5)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options(var. length)
Padding
Options :
copy :
class :
Debuging and special transmission modes
Option field reproduced in all fragments
0 = datagram or network control
2 = debuging and measurement
number : specifies the function of the option
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IP v4 Options
Class 0
Length
Option
– 1 : End of option list
– 2 : Security and handling restrictions
– 3 : Loose Source Routing
– 7 : Record route
– 9 : Strict Source Routing
1
11
var
var
var
Class 2
Option
– 4 : Internet timestamp
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var
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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
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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
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IP Networks
Router
1.2
3.2
1.1
1.3
4.1
4.2
4.3
3.3
5.2
2.1
1.4
2.2
5.1
5.3
6.1
7.2
7.1
2.3
6.2
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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 *)
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IP Networks
1.2 > 7.2
1.2
3.2
1.1
1.3
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
1
#1
direct
1.1
2.2
5.1
5.3
6.1
7.2
7.1
2.3
6.2
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IP Networks
1.2 > 7.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
1,2,3
4
>42.3
direct
3.2
2.2
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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IP Networks
1.2 > 7.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
2,5,6
1,3,4
72.3
direct
2.1
5.3
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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IP Networks
1.2 > 7.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
5,7
1,3,4
2.3
2,6
direct
5.2
5.1
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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IP Networks
7.2 > 1.2
1.2
3.2
1.1
1.3
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
7
#7
direct
7.1
2.2
5.1
5.3
6.1
7.2
7.1
2.3
6.2
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IP Networks
7.2 > 1.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
5,7
1,3,4
2.3
2,6
direct
5.2
5.1
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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IP Networks
7.2 > 1.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
3,4,5
1,2
2.3
6,7
direct
3.3
5.1
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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IP Networks
7.2 > 1.2
1.2
1.3
3.2
1.1
4.1
4.2
4.3
3.3
5.2
2.1
1.4
Dest.net
Forw.to
1,2,3
4
>42.3
direct
3.2
2.2
2.2
5.1
5.3
6.1
7.2
7.1
6.2
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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
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Classless InterDomain Routing
Class A :
0
Class B :
10
Class C :
110
Net (7)
Host (24)
Net (14)
Net (21)
Host (16)
Host (8)
• 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 !
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Classless InterDomain Routing
Class A :
0
Class B :
10
Class C :
110
MIT... :
INFOS1 :
WWW.IEEE
Belnet
44
Net (7)
00010010
18.
10000110
134.
11000111
199.
11000001
193.
Host (24)
Net (14)
Host (16)
Net (21)
xxxxxxxx
xxx.
10111000
184.
10101100
172.
10111110
190.
Host (8)
xxxxxxxx
xxx.
00000001
1.
10001000
136.
xxxxxxxx
xxx.
xxxxxxxx
xxx
01111101
125
00000001
1
xxxxxxxx
xxx
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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
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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 :
–y :
–z :
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11000010 00011000 00010001 00000100
11000010 00011000 00010001 00000100
11000010 00011000 00010001 00000100
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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
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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
»…
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ICMP error messages
Error causing IP packet
IP header
IP Data Area
Tr. header
Transport data area
IP header
IP header
Tr. header
ICMP error message
Error reporting ICMP packet
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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
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The Internet & Transport Layer
Applications Layer
Transport Layer
Internet Layer
Networks Layer
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The Transport Layer
is an end to end service
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Host A
Host B
Appl.
Appl.
Transp.
Transp.
Netw.
Netw.
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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
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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
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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)
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TCP segment format
TCP header
TCP Data Area
Source Port
Destination Port
Sequence Number
Acknowledgment Number
Off. | Res. | Code
Window Size
Checksum
Urgent Pointer
Options
padding
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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
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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
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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)
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UDP message format
UDP header
Source Port
Length
UDP Data Area
Destination Port
UDP Checksum
UDP header : 8 bytes
• 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
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UDP Port Numbers
(some examples)
•
•
•
•
•
•
•
•
•
•
61
0
7
11
13
17
53
67
68
69
123
Reserved
Echo
Users (Gives list of active users)
Daytime
Quote (Gives the quote of the day)
Domain (Domain name server)
BOOTPS (Bootstrap Protocol Server)
BOOTPC (Bootstrap Protocol Client)
TFTP (Trivial File Transfer Protocol)
NTP (Network Time Protocol)
12-06-K.Steenhaut & J.Tiberghien - VUB
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
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Network Address Translation
intranet
192.168.1.10
192.168.1.11
134.184.23.112
NAT
Internet
192.168.1.12
TCP and UDP
port numbers are abused to
identify the hosts on the intranet.
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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
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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
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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
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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
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IP v4 datagram format
IP header
IP Data Area
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
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IP v6 Header (1)
Ver Pri
Flow Label
Payload Length
Next Hdr Hop Lim.
Source IP Address
Destination IP Address
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IP v6 Addresses
128 bit addresses = 7. 1023 addresses / m2 on the earth !
Prefix
Allocation
Fraction
0000 001
0000 010
001
010
100
1111 1110 1
1111 1111
NSAP
IPX
Global unicast
Provider unicast
Geographic unicast
Local use addresses
Multicast groups
1/128 (0.8%)
1/128 (0.8%)
1/8 (12.5%)
1/8 (12.5%)
1/8 (12.5%)
1/512 (0.2%)
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
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IP v6 Unicast Addresses
Hierarchical addresses to facilitate routing.
3
13
8
001 TLA res
TLA:
NLA:
res:
SLA:
INT:
71
24
18
64
NLA
SLA
INT
Top level aggregation identifier (global ISP’s)
Next level aggregation identifier (within ISP)
reserve bits to be added to TLA or NLA in future
Site level aggregation identifier (local subnet)
Interface identifier on a specific subnet
(equivalent to v4 host identifier, but now, a single
computer can have several interfaces)
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Anycast Addresses
Unicast
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Anycast
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IP v6 Header (2)
Ver Pri
Payload Length
Flow Label
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, ...
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IP v6 Header (3)
Ver Pri
Payload Length
Flow Label
Next Hdr Hop Lim.
Source IP Address
Destination IP Address
Flow Label : an other step towards QOS control
Flow = connection oriented communication
implemented through connectionless service
Flow uniquely identified by
source address
flow label
Future routers could reserve resources for flows
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Bibliography
To 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
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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
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