Chapter 7 Intro to Routing & Switching. Upon completion of this chapter, you should be able to: ...
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Transcript of Chapter 7 Intro to Routing & Switching. Upon completion of this chapter, you should be able to: ...
TRANSPORT LAYER
Chapter 7
Intro to Routing & Switching
OBJECTIVES Upon completion of this chapter, you should be
able to: Explain the need for the transport layer. Identify the role of the transport layer as it provides
the end-to-end transfer of data between applications. Describe the role of two TCP/IP transport layer
protocols: TCP and UDP. Explain the key functions of the transport layer,
including reliability, port addressing, and segmentation.
Explain how TCP and UDP each handle key functions. Identify when it is appropriate to use TCP or UDP and
provide examples of applications that use each protocol.
LAYER 4 PROTOCOLS USED Each protocol does its’
own job IP addresses & routes
data Doesn’t say how it is
transported
Different applications use different protocols for transport of the data How data is
sent/exchanged
TCP or UDP
THE TRANSPORT LAYER
7.1.1
TRANSPORT LAYER INTRODUCTION What PDU?
Segments
Simply, the responsibilities: Ensures end-to-end delivery of data Establish a session between applications Segmenting the data Transport the data Handling the flow of data Reassembling the data Passing the data to the proper application Retransmit if necessary
TRANSPORT LAYER INTRODUCTION Protocols
TCP- most commonUDP
CONNECTION-ORIENTED PROTOCOL TCP Establish a connection 1st, then sends
data3-way handshakeSYN, SYN-ACK, ACK
CONNECTIONLESS PROTOCOL UDP No connection Doesn’t ensure error-free delivery Faster than TCP, more efficient for
quicker deliveryLive audio/video over Internet or VoIPTCP would bog it down; incomplete pics or
audio; pics wouldn’t coincide with audio
SEGMENTATION Large amounts of data broken into smaller
units Segments Also consider the MTU of the media 6000 byte message on a 1500 byte MTU
Ethernet 4 segments
Reassembled at destination
Sequencing Identifies the segments & helps is re-ordering
SEGMENTATION & REASSEMBLY Words split to send Dest. reassembles the words
Words may arrive out of orderSequence #’s help re-order into sentence
REVIEW- Q What is the PDU of the Transport Layer?
Segment What helps put a TCP segmented
message back in order at the destination?Sequence numbers
Which Layer 4 protocol could deliver data with errors or not be delivered at all?UDP
How is TCP able to establish a connection?3-way handshake
REVIEW- Q When sending a web page, which Layer
4 protocol would be used?TCP
In the same scenario as above, what would happen if the destination did not receive an ACK after sending data? It would re-send just that segment
Which layer 4 protocol is able to deliver data quickly?UDP
INTRODUCING TCP & UDP
7.1.2
TCP SUMMARY Connection-oriented Sends acknowledgements
Like tracking a FedEx delivery Breaks messages into small segments
If sender doesn’t get an ACK of message received, it retransmits
Only portion lost is resent On receiving host, TCP reassembles
data
FTP & HTTP are examples of protocols using TCP
TCP SEGMENT
TCP CONVERSATION
SEQUENCE #= 200SYN
SYN-ACK
SEQ#= 1450
ACK= 201
ACKSEQ#= 201ACK= 1451
TCP SLIDING WINDOW How much data it can receive
TCP END THE CONVERSATION
TCP SUMMARY Connection-oriented Guaranteed delivery 3-way handshake Segments & sequence # Acknowledgements Flow control Retransmission
Generates more traffic because of all this
REVIEW- Q What significance does the ACK# have?
It’s the next expected byte numberSequence # received PLUS 1
When a conversation is ready to end, nothing more is being sent, what flag gets sent?FIN
What are 2 protocols that use TCP?HTTP & FTP
Explain flow control.Adjusting the amount/flow of data being
sent/received
UDP
7.2.3
UDP Connectionless Used for faster transmissions Low overhead “Best effort delivery”
Regular mail / no guarantee of delivery No ACK or retransmission No error checking* Used for streaming audio, video, VoIP
DNS, DHCP, TFTP, VoIP, Gaming, SNMP are examples of protocols that use UDP
UDP HEADER
Source Port Destination Port
Length Checksum
Data
UDP INTERRUPTIONS
USE TCP OR UDP? TCP
HTTP IPFTPTelnetSMTP/POPDNS
UDPDHCPTFTPSNMPVoIP Internet TV/RadioDNS
COMPARING TCP & UDP
UDP TCP
Faster Best effort delivery No
acknowledgements No retransmit
Connectionless
Slower Segments Acknowledgements Retransmission Reassembles Connection-
oriented Flow control
ACTIVITY 1
ACTIVITY 2
REVIEW- Q
TCP-WHAT DO YOU REMEMBER? Which is connection-oriented?
TCP TCP establishes a connection or a ________
with the destination.Session
Why is TCP reliable?Sends acknowledgments of receiving &
retransmits missing data Explain flow control for TCP.
Regulates the flow of data Protocols used?
HTTP, SMTP, Telnet, FTP
UDP-WHAT DO YOU REMEMBER? Speed?
Fast Connection or connectionless?
Connectionless Reliability?
UnreliableNo ACK or retransmission
Flow control?None
Protocols used:DNS, VoIP, Video Stream, SNMP
TRACKING THE CONVO You have many conversations at the
same timeWebEmailDHCPVoIPVideo streaming
Transport Layer tracks each one
MANY CONVOS, ONE STREAM All of those conversations come out as
one stream of dataExample: your streaming video coming in
does not take up the entire connection
Multiplexing (sending) Demultiplexing (receiving)
This is what it does…………………………………
PASS DATA TO APPLICATION Sends data to proper application
Your many conversations: Web goes to web browser Email goes to email program DHCP goes to IP config VoIP goes to VoIP software Video streaming goes to media player
Each protocol has a port # In the segment to direct to the correct
application
PORT NUMBERS All the conversations need to be tracked
Port Number in each segmentHelps identify what service the message is
for Web request, email, DHCP, etc.
Protocols identified by port numbers
PORT # EXAMPLE
PORT # & COMMUNICATION Each message sent, has a source &
destination port number Source Port
Randomly generated & placed into segmentTracks incoming segment
Destination PortUsed to pass data to proper application at
destination
REVIEW- Q
PORT NUMBERS 1-65,535 Well-known ports
1- 1023Common applications
Registered ports1024- 49,151Can be source or destination portsUsed for specific applications like IM
Private ports49,152 & above For source ports
IMPORTANT PORT #’S Destination- tells about service
requested20 & 21- FTP23- Telnet25- SMTP53- DNS (BOTH TCP & UDP)67 & 68- DHCP69- TFTP80- HTTP110- POP3161- SNMP443- HTTPS
SOCKETS
The combo of the source & destination IP AND the source & destination port number is known as a socket. 192.168.1.7:80
CHECK IT! Check your active connections
Unexplained ones could be threats! C:\> netstat
ACTIVITY 7.1.2.11 Drag each description to TCP or UDP
REVIEW-
REVIEW-
SENDING A MESSAGE Web Server to client (you)
Application data broken into TCP segments Each segment has a header w/ source & dest
portsSegment encapsulates HTTP & HTML dataEncapsulates into a packet w/ IP header
IP header has source & dest IP addresses IP Packet sent to Ethernet protocol
Encapsulates into frame header & trailer Source & destination MAC AND error checking
Bits encoded onto the media
RECEIVING THE MESSAGE Last process in reverse
Bits received by NIC & decoded Destination MAC recognized
Ethernet header & trailer removed Source & dest MAC removed
IP header removed Source & dest IP removed
TCP header removed Source & dest ports removed
Web page data passed to HTTP & browserTCP segment received, reassembled, &
page displays
ACTIVITY 192.168.5.101
80 or TCP or UDP
01-5A-FF-65-80-DC
1100101101000010
DHCP or POP3 or HTTP
REVIEW- 4Q
REVIEW- 3Q
REVIEW & STUDY Complete the study guide handout
Take the quiz on netacad.com
Jeopardy review
SUMMARYIn this chapter, you learned: The role of the Transport layer is to provide three
main functions: multiplexing, segmentation and reassembly, and error checking.
These functions are necessary in order to address issues in quality of service and security on networks.
Knowing how TCP and UDP operate and which popular applications use each protocol will allow the implementation of quality of service and build more reliable networks.
Ports provide a “tunnel” for data to get from the Transport layer to the appropriate application at the destination.
TRANSPORT LAYER
Chapter 7
Intro to Routing & Switching