Transcript DCN286 INTRODUCTION TO DATA COMMUNICATION TECHNOLOGY TCP/IP Transport and Application protocols

DCN286 INTRODUCTION TO DATA
COMMUNICATION TECHNOLOGY
TCP/IP Transport and Application
protocols
TCP/IP model
Data unit
ISO/OSI
Layer
Description
DoD Model
Layer
Data
Application
Network processes to applications
Application
Presentation
Data representation and encryption
Session
Interhost communication
Segment
Transport
End to end connection
Transport
Packet
Network
Logical address and best routing
path
Internetwork
Frame
Data Link
Physical addressing
Network
Interface
Bit
Physical
Binary transmission
TCP and UDP
The two important Transport layer protocols:
They help to transfer data from one application
process on one computer to the correct
application process on another computer.
 TCP (Transmission Control Protocol)
Connection-oriented protocol, more reliable and
slower.
 UDP (User Datagram Protocol)
Connection-less, faster, simpler and not reliable
(no error checking).
TCP and UDP comparison
Features
Flow control and windowing
TCP UDP
Yes
No
Connection-oriented
Yes
No
Error recovery
Yes
No
Segmentation and reassembly of data
Yes
No
In-order delivery of data
Yes
No
Identifying application using port
numbers
Yes
Yes
To use TCP or UDP (optional)
Protocol
TCP
TCP
TCP
TCP
TCP, UDP
UDP
TCP
TCP
UDP
UDP
Application
FTP data
FTP Control
Telnet
SMTP
DNS
TFTP
HTTP (web)
POP3
SNMP
RIP
Flow Control
Receiver needs time to process data
and inform sender how fast the data
could be sent to it. Two methods to
control flow:
*Dynamic sliding windows
**Withholding acknowledgments
Dynamic Sliding Windows
1. Receiver advises window (size of data
limit)
2. Sender keeps sending data until the
limit. Stop and wait for ACK.
3. Receiver processed data and sent
ACK and next window value to sender.
4. Sender starts sending data until reach
the limit. Then, wait for ACK and next
window value.
Withholding Acknowledgments
Another option of receiver is wait to send ACK.
1. Receiver informs sender the window size.
2. Sender keeps sending data until limit of
window.
3. Receiver only sends out ACK after
complete the processing
4. Sender receives ACK and window size and
starts next round sending.
Window
The max value of data sender can send
before an acknowledgment.
TCP Three way handshake
1. First segment has a SYN flag but does
not have the ACK flag set. (SYN=1 and
ACK=0)
2. The second has both SYN and ACK set
3. The third and ongoing segment have
only ACK
TCP error recovery (reliability)
TCP acknowledges the receipt of data by the
Acknowledgment Number filed of the TCP
header.
It identifies the next byte expected to be received.
NOT the last byte received.
Sender  1000  1002  1003  Receiver
Sender  1001  Receiver (because received
1000)
Segmentation
TCP received data from application protocols
and break them into small pieces for
transmission. TCP header is put in front of
each chunk.
Maximum Segment Size (MSS) : max length of
TCP data filed. Ethernet frames allow 1500
data bytes in data field. TCP and IP header are
20 bytes each. 1460 is the MSS in Ethernet
Reassembly and in-order delivery
In-order delivery: Sent by sequence.
Reassembly: according to the SEQ number.
Receiver may temporary store segments
into memory and wait for other segments
for reassembly by sequence.
TCP and UDP header
 TCP header
2 bits
2
4
4
4
6
6
2
2
2
3
1
Source
port
Dest.
Port
Seq
Number
Ack
Number
Offset
Reserved
Flags
Window
Size
Chec
k sum
Urgent
Options
PAD
 UDP header
2
Source
Port
2
Dest Port
2
Length
2
Checksum
Port number
Application may use multiple port numbers in
the same time. A unique port number is
needed for each TCP or UDP connection.
Such port numbers are dynamic port number. A
host can dynamic allocate 1024 (2^10) to
65,535 (2^16) port numbers
Uses of port number
Type of port
Dynamic
Range of port Purpose
number value
49,152Allocated by client for each
65,535
new application process
Well-known
0-1023
Registered
1024-49,151
For high privilege
processes, used so that all
clients know the correct
port number
Equivalent to Well-known
port, but for nonprivileged
application process.
Well-known ports
Port number
20
21
23
25
53
69
80
110
161
520
Protocol
TCP
TCP
TCP
TCP
TCP, UDP
UDP
TCP
TCP
UDP
UDP
Application
FTP data
FTP Control
Telnet
SMTP
DNS
TFTP
HTTP (web)
POP3
SNMP
RIP
Application layer
In DoD model, application layer, application
protocols define the format of the data being
transferred (such as binary or ASCII text);
encryption and the rules for transferring data.
In ISO/OSI model, application layer is only
responsible for application interface. Encryption
is in Presentation layer which is also responsible
for data representation. Session layer is to
combine message communication between
hosts.
DNS (Domain Name Service)
 Tranlate between Full Qualified Domain
Name and IP address.
Domain name is in human language such as
www.cisco.com and IP address is in the
numbering format.
Top level domain could be in 3 categories:
1. Tradition: .com, .net, .edu, .gov, .mil, .org
2. Country code: ck, uk, jp, pl, ru, etc, etc.
3. New released: .info, .aero, .museum,
.name, .coop, .biz, .pro.
HTTP (Hypertext Transfer Protocol)
 Application layer protocol
 Distribute, collaborate and retrieve inter-linked resource from
web pages
 Default port is 80 (*could use different port)
 Typical requests:
 Head: asks for the meta-information
 Get: requests a representation of the specified resource.
 Post: submit data to be processed
 Put: Uploads a representation of the specified resource.
 Delete: Deletes the specified resource.
 Trace: echoes back the received request
 Options: returns the HTTP methods that the server supports for
specified URL
HTTPS (Hypertext Transfer Protocol Secure) (Optional)
HTTPS is a combination of the HTTP and a
network security protocol
HTTPS has also been known as "Hypertext
Transfer Protocol over Secure Socket Layer",
but now HTTPS may be secured by the
Transport Layer Security (TLS) instead of
Secure Sockets Layer (SSL) protocol.
An https: URL may specify a TCP port. If it
does not, the connection uses port 443
(unsecured HTTP typically uses port 80)
HTML, DHTML and XML (Optional)
 HTML (HyperText Markup Language): the
predominant markup language for Web pages.
 DHTML (Dynamic HyperText Markup Language): is
a collection of technologies used together to create
interactive and animated web sites by using a
combination of a static markup language (such as
HTML), a client-side scripting language (such as
JavaScript), a presentation definition language
(such as CSS), and the Document Object Model.
 XML (Extensible Markup Language): is a generalpurpose specification for creating custom markup
languages. It can perfectly present shared
structured data.
Sample code of HTML (optional)
Sample html code:
<!DOCTYPE html>
<html>
<head>
<title>Title bar display</title>
</head>
<body>
<p>Hello This is my page!!</p>
</body>
</html>
Web server (optional)
The web server is to
Host web pages
Answer HTTP requests
Logging clients visits
Offer authentication if it is required
Bandwidth throttling
Could be running on Windows IIS or
Unix/Linux system
Web client and browser (optional)
Web clients are using browser to display and
interact with text, images, videos, music, games and
other information typically located on a Web page at
a Web site on the World Wide Web or a local area
network.
Typical browsers:
Internet Explorer,
Opera,
Mozilla Firefox,
Safari,
Avant Browser
Maxthon,
AOL Explorer
E-Mail protocols: SMTP, POP3 and IMAP
 SMTP (Simple Mail Transfer Protocol) is an Internet
standard for electronic mail (e-mail) transmission
across Internet Protocol (IP) networks.
 POP3 (Post Office Protocol version 3) is an
application-layer Internet standard protocol used by
local e-mail clients to retrieve e-mail from a remote
server over a TCP/IP connection.
 Internet Message Access Protocol (commonly
known as IMAP or IMAP4, and previously called
Internet Mail Access Protocol, Interactive Mail
Access Protocol and Interim Mail Access Protocol
is an application layer Internet protocol operating
on port 143 that allows a local client to access email on a remote server.
Email access (optional)
Web mail (hotmail, yahoo, gmail, and
exchange web access)
Outlook
Outlook express
Telnet
Blackberry (BIS and BES)
Many freeware: courier, Eudora, Foxmail,
Opera Mail, Window Live Mail, etc, etc.
telnet smtp.example.com 25 (optional)
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S: 220 smtp.example.com ESMTP Postfix
C: HELO relay.example.org
S: 250 Hello relay.example.org, I am glad to meet you
C: MAIL FROM:<[email protected]>
S: 250 Ok
C: RCPT TO:<[email protected]>
S: 250 Ok
C: DATA
S: 354 End data with <CR><LF>.<CR><LF>
C: From: "Bob Example" <[email protected]>
C: To: Alice Example <[email protected]>
C: Date: Tue, 15 Jan 2008 16:02:43 -0500
C: Subject: Test message
C:
C: Hello Alice.
C: This is a test message with 5 headers and 4 lines in the body.
C: Your friend,
C: Bob
C: .
S: 250 Ok: queued as 12345
C: QUIT
S: 221 Bye
{The server closes the connection}
File transfer application protocols
HTML can also be used to transfer files
TFTP: is faster and using UDP port 69
FTP: support authentication and using TCP
port 20 and 21
FTP (TFTP) server hosts the files and
documents in a structured directory tree.
Client uses various programs to get, upload files
and documents. The programs could be
SmartFTP, FileZilla, CuteFTP, WISE-FTP, etc,
etc.
Telnet
 Telnet is a network protocol used on the Internet or
local area networks
 The term telnet also refers to software which
implements the client part of the protocol. Telnet
clients are available for virtually all computer
platforms. (Start  Run “cmd”  telnet /?)
 The client-server protocol is using TCP port 23 by
default. And it does not encrypt any data sent over
the connection (including the password). Thus, all
information can be captured by network sniffer.
SSH (optional)
Secure Shell or SSH is a network protocol
that allows data to be exchanged using a
secure channel between two networked
devices.
SSH was designed as a replacement for
TELNET which is an insecure remote
shells and transfer password in clear text
format.
SNMP (Simple Network Management Protocol)
An SNMP-managed network consists of three
key components:
Managed devices (a computer or a network
host such as router and switch)
Agents (software running in the managed
devices)
Network-management station (central
management work station in which
application server is executed)
It is possible to configure a Cisco router as a
SNMP server
What is the Network address of
172.16.132.70/20?
Another Example of Network Address
172.16.4.35/27
Host Address
Binary Host
Address
Binary Subnet
Mask
Binary
Network
Address
Network
Address
172.
16.
4.
35
10101100 00010000 00000100 00100011
11111111
11111111
11111111 11100000
10101100 00010000 00000100 0010000
172.
16.
4.
32
Private IP address
Just to remember
Certain blocks are reserves as private IP address used in company /
organization internal networks. More computers could have “unique” IP
address in IPV4.
Class Range of IP
address
Range of
Network number
Default network
mask
Total number
of networks
1
A
10.0.0.0 –
10.255.255.255
10.0.0.0 –
10.0.0.0
/8 (255.0.0.0)
B
172.16.0.0 –
172.31.255.255
172.16.0.0 –
172.31.255.255
/12 (255.240.0.0) 16
C
192.168.0.0 –
192.168.0.0 –
/16 (255.255.0.0) 256
192.168.255.255 192.168.255.255
Thus, it is possible for many companies / organizations using same
network address internally. (For instance, 10.10.10.10 could be used for
computer Tom in company Apple and by computer Jerry in company
Boss) But, again, the potential duplicated addresses are used internally.
Class B table
# of bit
borrowed
Subnet Mask
# of Usable
Subnets
# of available
Hosts
.11000000.00000000
255.255.192.0
4
16,382
.11100000.00000000
255.255.224.0
8
8,190
.11110000.00000000
255.255.240.0
16
4,094
.11111000.00000000
255.255.248.0
32
2046
.11111100.00000000
255.255.252.0
64
1022
.11111110.00000000
255.255.254.0
128
510
.11111111.00000000
255.255.255.0
256
254
.11111111.10000000
255.255.255.128
512
126
.11111111.11000000
255.255.255.192
1024
62
.11111111.11100000
255.255.255.224
2048
30
.11111111.11110000
255.255.255.240
4096
14
.11111111.11111000
255.255.255.248
8192
6
.11111111.11111100
255.255.255.252
16384
2