Wednesday, February 10, 2016

CCNAv1 Chapter 7 Notes - Transport Layer

Transport Layer Chapter 7       
Role: Establishes a temporary connection called a session between two applications and delivers data between them.
  • It is the link between the application layer and the lower layers.
  • Provides a method of delivering data across the network in a way that ensures the data can be reassembled at the receiving end.
  • Primary Protocols for this layer are TCP and UDP.
    • TCP
      • Reliable
      • Gets acknowledgements.
    • UDP
      • “Best Effort”
      • Fast
      • Doesn’t get acknowledgements.

Segments need to be segmented and reassembled at the other end. The mechanism used is called ‘Header info’.
Application that generated the segment is identified via a port number.

Multiplexing: Multiple conversations (packets) that interweave with each other.



TCP
UDP
  • Connection Oriented (Session)

  • Reliable Delivery / Flow Control

  • Ordered Data Reconstruction

  • Stateful Protocol
           (Keeps track of conversations in a session      through acknowledgments)

  • 20 bytes of overhead per segment
  • Connectionless

  • Unreliable

  • No Acknowledgements

  • 8 bytes of overhead per segment


Port Addressing (Sockets) (Example)
  • 192.168.1.5:80 (HTTP)
  • 192.168.1.5:21 (FTP)
  • 192.168.1.5:23 (Telnet)

‘Well Known Ports’ Port #’s: 0 - 1023 Reserved for Applications
‘Registered Ports’ Port #’s: 1024-49151 Assigned to Applications
‘Private Ports’ Port #’s: 49152-68535 Assigned dynamically as needed.


11/5 - Review of previous quizzes; chapter 7 & 7.2
  • What term is used to describe the interleaving of data from multiple users in the same network?
    • Multiplexing
  • What is used by the transport layer to identify an app or service?
    • Port
  • What TCP header field specifies the # of segments that can be accepted before an ack is required?
    • Window Size
  • Which TCP control bit is set to on to terminate a TCP connection.
    • 3 way handshake
  • What two flags in the TCP header are used to establish connectivity?
    • SYN + ACK
        • A -> SYN
        • B -> SYN/ACK
        • A -> ACK
Protocols
  • Window Size Telnet  = TCP
    • .TCP DHCP = UDP
  • Connectionless TFTP = UDP
    • UDP FTP = TCP
  • Port Number HTTP = TCP
    • .BOTH
  • Best for VOIP
    • .UDP
  • 3-Way Handshake
    • TCP
  • Checksum
    • BOTH

Socket - IP Address and Port
Multiplexing - Conversation between multiple
Port #’s - Used for applications to identify conversation.
Window Size -
UDP/TCP
Ack - Acknowledges a message from another system
Syn -  Synchronize
Fin - “Done”, no more info to send to other.

How many steps does it take to set up a connection?
-- 3 Steps:
1: SYN ----> 2: ← SYN, ACK 3: ACK ---->
Sequence # (Seq #) { TCP Header
Acknowledgement (Ack#)
Confirm Receipt of Data

TFTP -> Sending Data -> 1st packet lost? This packet is what? UDP

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