Transport Layer Flashcards
(20 cards)
Transport Layer Responsibilities
*Tracking individual Conversations
*Segmenting Data and reassembling Segments
*add Header Information
*Identifying the Application
*Conversation Multiplexing
Hauptaufgaben von Transport Layer
*Garantie, dass Packet ankommt und korrekt reassambled wird
*Individuelle Verbindungen mittels Port unterscheiden
Characteristics of UDP
*Fast
*Low overhead (8 Bytes)
*no acknowledgement
*no resend of lost data
*delivers data as it arrives
Characteristics of TCP
*reliable
*aknowledeges data
*resends lost data
*delivers data in sequenced order
Transport Layer Protocols
*UDP (User Datagram Protocol)
*TCP (Transmission Control Protocol)
TCP is…
connection-oriented (3-way handshake)
UDP is…
connectionless
3-way handshake
*syn
*syn ack
*ack
4-way handshake
*fin
*ack
*fin
*ack
(terminates host and server sequence number thus 2+2)
What happens when you don’t terminate a session properly with fin ack fin ack
RAM overload
Can only provide TCP a reliable delivery?
No, can be implemented in the Application Layer
Data loss and retransmission methods
*Ack (all previous segemnts are ok, but resend from segment x on)
*SACK (Selective ACK, deliver segment x - y)
What is MSS?
*Maximum Segment Size
*max 1460 Bytes (1500 Bytes - 20 Bytes IPv4 Header - 20 Bytes TCP Header)
When will the Sliding Window as well as the MSS be defined?
3-way handshake
What happens with the Sliding Window?
When an ack message will be received, the window is adjusted to send further segments.
Port numbers are used to
deliver the data to the right application / service
TCP Flow Control allows
to request that the sending application reduces the rate of data flow
Size of TCP and UDP Header
*TCP = 20 Bytes
*UDP = 8 Bytes
Types of Ports and their ranges
*Well-known (0 - 1023)
*Registered (1024 - 49151)
*Private and or Dynamic Ports (49152 - 65535)
Primary benefits of segmenting?
*increased speed (allows multiplexing)
*increased efficiency (if a single segment fails, only this has to be resend)
