CCNA Exploration Semester 1-Chapter 4 pot

Chapter 4 Transport Layer Overview  Explain the role of Transport Layer protocols and services in supporting communications across data networks  Analyze the application and operation of TCP mechanisms that support reliability  Analyze the application and operation of TCP 2  Analyze the application and operation of TCP mechanisms that support reassembly and manage data loss.  Analyze the operation of UDP to support communicate between two processes on end devices Transport Layer Overview Transport Layer TCP UDP 4  Transport Layer: Responsible for creating and maintaining a logical connection between the endpoints  What are the two protocols at the transport layer? TCP – Transmission Control Protocol UDP – User Datagram Protocol Transport Layer Role and Services  Major functions of the transport layer and the role it plays in data networks – Tracking the individual communication between applications on the source and destination hosts. – Segmenting data and managing each piece. – Reassembling the segments into streams of application 5 – Reassembling the segments into streams of application data. – Identifying the different applications TCP Header UDP Header What is the application PDU called? 6 Application Header + data or PDU: Segment PDU: Data What is the transport PDU called? Transport Layer www.cisco.com TCP Segment 7  Primary responsibilities: Tracking the individual communication between applications Who is the client? Which application? Which process? Identifying the different applications (HTTP, FTP, etc.) Segmenting data Managing each segment Reassembling the segments TCP Segment TCP Segment TCP Segment  What two protocols are at the Transport Layer? segment segment 8 TCP UDP  IP is a best-effort delivery service. What does that mean? No guarantees Best-effort service “Unreliable service”  TCP/UDP is responsible for extending IP’s delivery service between two end systems. TCP vs. UDP  TCP provides: Reliable delivery Error checking Flow control  UDP provides: Unreliable delivery No error checking No flow control Why would any application use UDP? What is the “cost” of all this reliability and flow control of TCP? Streaming media, real-time multiplayer games and voice over IP (VoIP) applications that do not require reliability mechanisms and may even be hindered by them. 9 Flow control Congestion control Ordered delivery Connection establishment Applications: HTTP FTP Telnet MSN messenger No flow control No congestion control No ordered delivery No connection establishment Applications DNS (usually) SMTP DHCP RTP (Real-Time Protocol) VoIP TCP TCP TCP HTTP HTTP FTP SMTP Cabrillo Web Server ISP’s 10  A single client may have multiple transport connections with multiple servers.  Notice that TCP is a connection-oriented service (two-way arrow) between the hosts, whereas UDP is a connectionless service (one-way arrow) . (later) TCP TCP TCP TCP UDP UDP ISP’s Email and FTP Server [...]... port of client) Source Port = 23 (telnet) 22 49 888 49 890 Same client to same server - Two different HTTP sessions Client: Same destination port Client: Different source ports to uniquely identify this web session 23 49 888 49 890 C:\Users\rigrazia>netstat -n Active Connections TCP or UDP Proto TCP TCP Source Port Local Address 192.168.1.101 :49 888 192.168.1.101 :49 890 C:\Users\rigrazia> Destination Port Foreign... 198.133.219.25:80 198.133.219.25:80 Source IP Connection State State TIME_WAIT TIME_WAIT Destination IP 24 192.168.1.101 Source Port 49 888 49 890 Destination Port 198.133.219.25 80 80 80 172.16.5.5 Source Port 49 888 www.cisco.com What makes each connection unique? How does the server know which source port 49 888 is who? Connection defined by the pair of numbers: Source IP address, Source port (From Client... Client: TCP source port Server: TCP destination port May also include the range of Registered Ports (Numbers 10 24 to 49 151) 18 Client Server Telnet 19 Client TCP Header 0 15 16 1028 16-bit Source Port Number 31 16-bit Destination Port Number 23 32-bit Sequence Number 32 bit Acknowledgement Number 4- bit Header Length 6-bit (Reserved) U A P R S F R C S S Y I G K H T N N 16-bit TCP Checksum 16-bit Window Size... (Numbers 10 24 to 49 151) Assigned to user processes or applications Non-common applications Client: TCP destination port Server: TCP source port May also be used as dynamic or private port (next) Well Known or Registered Port Number 17 Private/Dynamic Port Number Well Known or Registered Port Number Well Known or Registered Port Number Private/Dynamic Port Number Dynamic or Private Ports (Numbers 49 152 to 65535)... Number 14 http://www.iana.org/assignments/port-numbers The Internet Assigned Numbers Authority (IANA) assigns port numbers 15 Well Known or Registered Port Number Well Known Ports (Numbers 0 to 1023) Reserved for common services and applications Client: TCP destination port Server: TCP source port Well Known or Registered Port Number 16 Well Known or Registered Port Number Registered Ports (Numbers 10 24. ..Port Numbers: TCP and UDP UDP Header TCP Header 0 15 16 16-bit Source Port Number 31 16-bit Destination Port Number 32-bit Sequence Number 32 bit Acknowledgement Number 4- bit Header Length 6-bit (Reserved) U A P R S F R C S S Y I G K H T N N 16-bit TCP Checksum 16-bit Window Size HTTP is Port 80 16-bit Urgent Pointer Options (if any) Data (if any) Both TCP and UDP use... Port: 1028 (Dynamic Port assigned by client) Server 20 Server TCP Header 15 16 0 23 16-bit Source Port Number 31 16-bit Destination Port Number 1028 32-bit Sequence Number 32 bit Acknowledgement Number 4- bit Header Length 6-bit (Reserved) U A P R S F R C S S Y I G K H T N N 16-bit TCP Checksum 16-bit Window Size 16-bit Urgent Pointer Options (if any) Data for Telnet Data (if any) Client Server responds... UDP segment Receiver UDP adds 16 bit ‘words’ keeping a cumulative sum Adds 1’s (ones) complement If no errors are introduced into the segment, then the Total at the receiver will be 1111111111111111 34 UDP Checksum (FYI) 0 15 16 Client Server 31 16-bit Source Port Number 16-bit Destination Port Number 16-bit UDP Length 16-bit UDP Checksum Time Data (if any) Cumulative Sum: 1100101011001010 1s complement: . Port Number 17 Port Number Well Known or Registered Port Number  Registered Ports (Numbers 10 24 to 49 151) Assigned to user processes or applications. Non-common applications. Client: TCP destination. port Server: TCP destination port May also include the range of Registered Ports (Numbers 10 24 to 49 151) Well Known or Registered Port Number Private/Dynamic Port Number Well Known or Registered. information to the upper layers. 32 - bit Sequence Number 32 bit Acknowledgement Number 4- bit Header Length 6-bit (Reserved) U R G A C K P S H R S T S Y N F I N 16-bit Window