LearningByTweeting
@hci_go
I'm a CS student at University of Trento. I'm using Twitter to check the level of my studies for the coming exams #network #java #softEng #cybersec #compilers
The cause n1 of #congestion is no space resource through the #network: #segments lost, higher #traffic, more congestion. 2 algorithm to manage #cwnd: #slowStart, #congestionAvoidance. SS increases cwnd at each RTT of a 2factor, while CA increases of 1 MSS at each cycle of cwnd.
RTO is calculated with formula: SRTT+4RTT. These parameters are generated from the behavior of the #net and the actual value of previous RTT. If segment has not been acknowledged after 1 RTO than the transmitter will wait for 2 RTO. The min RTO is 200 ms and the max RTO is 60sec
How to start connection? SYN(portA,portB,ISN-A); SYN(portB,portA,ISN-B,ACK). MSS defaut:1500Bytes. Depends on MTU IP & Datalink protocol. Gentle closure (FIN,ACKFIN x 2) substituted by RST (resources immediately released) to avoid #DoS attacks. RTO depends on the RTT estimation.
#TCPheader: #sourcePort, #destinationPort, #sequenceNumber, #acknowledge number, header length, reserved #bits, bit for settings(URG,ACK,PSH,RST,FIN,SYNC), receiver window->window_scale, checksum, urgent pointer. Min 20Bytes, TCP without #windowScale can be neck bone of Internet
Flow control implemented using #ACK indicating the available space of #receiver window. When #transmitter window is bigger than #bottleneck, #data stored in #buffers, so #RTT gets higher and #throughput gets lower. #PDU from 20Bytes #HEADER to #MSS derived from superior levels.
Performance of #Window protocol is measured by (LengthPacket/TransmissionRate) / RoundTripTime+(LengthPacket/TransmissionRate). Stop&Wait is non-performing when RTT is dominating the use function. Pipelining in #TCP is better: trasmission speed is DimensionTrasmissionWindow/RTT.
Flow is uniquely identified by 5-uple: source&destination port, s&d IP address, transport protocol. #UDP format identifies s&d port, length, checksum (like bit-equality, majorityBit). Transfer window is quantity of #PDU which transmitter can send before receiving #ACK after #RTT.
#TransportLayer used 4 creating means for logical communication between network layer & application processes through #sockets on ports. Main #protocols are #TCP & #UDP: first connection-oriented w/ #congestion control, while UDP is #stateless. Public services on port under 1024.
Today it's #transport layer's day for my study path. #Networks #TCP #UDP
That's all for today. Now it's @DataCamp time with the new course "Python Data Science Toolbox (Part2)". See ya! #python #DataScience
#FTP is File Transfer Protocol. Used to transfer files with best-effort approach. The goal isn't to reduce #latency, but guarantee that file arrives. The Out Of Band approach is used with #port21 for connection control and #port20 for data connection. FTP is #statefull #protocol
#VoIP is a #multimedia #application service based on IP connectivity through an end-to-end service. Differently from the traditional telephone #network, with the #Internet the intelligence is no longer INSIDE the network but at its boundaries: VoIP is one example of this concept.
#DNS is huge distributed database implemented with tree-hierarchy structure of so called DNS-servers. It's goal is translating the host name with #IP address. The Resource Record has standard format with name,value,type (A, NS, CNAME, MX),ttl. Requests are iterative or recursive.
I'll try to tweet in english and/or in italian every day. 3 tweet relate to key concepts for each course.
I'll tweet some notes regarding the courses I'm currently studying: #network #java #SoftwareEngineering #CyberSecurity #FormalLanguagesCompilers
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