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Questions tagged [transport-protocol]

For questions about or in relation to the transport protocol or OSI layer 4. For instance the best-known transport protocol of TCP/IP is the Transmission Control Protocol (TCP).

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Of what layer is socket a concept?

In network layer, IP address is a concept. In transport layer, port is a concept. Is socket a concept of transport layer? If not, what is the corresponding concept to socket in transport layer? Of ...
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Do different IP addresses correspond to nonoverlapping sets of ports?

If a network interface has two different IP addresses 1 and 2 assigned to it. and the port numbers in (IP address 1, port number) and (IP address 2, port number) are the same number, does it mean the ...
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How do TCP connections work?

The TCP establishes a connection between the source and the destination. My questions are: What do we mean by end-to-end communication? What is the role of that connection?Couldn't reliability be ...
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How does a TCP segment fit into a smaller IP packet?

The IP protocol can handle fragmentation and it includes the fragmentation offset and identifier. I know this comes into play when your IP packet is too big for some specific network or link where the ...
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How does the transport layer tell UDP apart from TCP?

So I'm reading Computer Networking: A top down approach (where these images are from) and I was looking at the Transport layer. A generic segment in the transport layer has a pretty simple structure: ...
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How MPTCP closed connection?

how MPTCP connection with more than one subflow closed? what would happen to MPTCP connection if a client decide to close one of the subflows? it would be very kind of you if you explain it step by ...
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Understanding acknowledgement mechanism in sliding window protocol

I came across following problem: Node A sends packets to B through router R. The link A-R is instantaneous , but the R->B link transmits only 1 packet each second , one at a time . Assume A sends ...
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acknowledgment by TCP does not guarantee that the data has been delivered

In RFC 793 there is a part about the acknowledgment of TCP segments: When the TCP transmits a segment containing data, it puts a copy on a retransmission queue and starts a timer; when the ...
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How can a UDP Client and a packet sniffer run on the same machine?

In my understanding, if you have a UDP socket client that is bound to a particular port, then a second UDP client on the same machine can't bind to the same port. If this is the case, then how can a ...
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tcp connection and stream flow question

Could anyone explain the main principe of tcp flow when making a session ? I have take a tcp dump when i'm trying to browse a site. when I analyse the packet by wireshark, i have found many Three way ...
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Is it possible to implement virtual network based on MAC in IP instead of MAC in UDP?

We know that flannel use MAC in UDP to create a overlay network. My question is: UDP header only provides an extra port number fields, let's suppose that one physical machine only run one flanneld ...
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Question about output of 'lsof -i' and UDP being connectionless

I'v got a simple setup: Server (IP 10.0.0.33) listening on port 7770 using the command: $ netcat -lup 7770 And a client (IP 10.0.0.2) that communicates with the server using: $ nc -u 10.0.0.33 ...
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How does the Transport Layer construct the Pseudo-Header for TCP checksum?

THE TCP Psuedo Header needs sender and destination IP Address and protocol type. All of this informations is present in the network layer/IP header. Since the transport layer cannot access the data ...
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How could a response be sent to the requestor without requestor's address?

I'm reading this talking about the differences between two fire-and-forget message (for example, under UDP) and a request-response communication (for example, under TCP). I came across this: The ...
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Processing received SACK information in case of reordering

I would like to understand how TCP receiver in established state should treat SACK information of out-of-order and fully within receive window segments, where rcv_nxt < seq_no < rvc_nxt + ...
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Why is a TCP Socket identified by a 4 tuple?

Newbie to networking here. I'm reading the Computer Networking (3rd edition) book, and in section 3.2 they are discussing multiplexing / demultiplexing for both UDP and TCP. In the UDP protocol, a ...
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How can a TCP window size be allowed to be larger than the maximum size of an ethernet packet?

I know that TCP window sizes can be scaled to over 64KB, but looking at an ethernet packet datagram, such as this one: it looks like a layer 2 packet is limited in size to be much smaller than that. ...
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Questions about TCP packets

I am currently in college learning about networks, and I just wanted to make sure that I understood part of the TCP correctly. The question is "What does TCP use to reassemble packets in the correct ...
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Session ID vs Port number

How does the session ID differ from the port number? at the Application layer, Port Number Identifies the service, same for session layer. right? and these port numbers are assigned at Transport layer....
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How TCP and firewall handle security?

I'm a newbie in networking, still don't quite understand about security. Let's say a person A uses TCP to establish a TCP connection with a server. And there is a hacker B who is sniffing, so B ...
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Sender and Receiver timers in GBN, SR and TCP?

So basically for each of the GBN, SR and TCP's retransmission method, i have 2 question: 1.Is there a Timeout timer for EACH packet or one timeout timer for all of the packets? 2.Is there a ...
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Computer networking dwdm [closed]

Why do we use digital cross connects, which define permanent cross connect between source and destination in core network while the PSTN allocated circuits dynamically as both are types of circuit ...
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TCP close 2-way handshake with tcpdump package

Well, I got a pcap package that uses the tcpdump command. In this pcap, the TCP closes in 2-way handshake! Questions: In this picture, can anyone determine who initiated the signal to close the ...
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Why is ARQ (Automatic Repeat reQuest) named so?

I can't make sense of a naming for Automatic Repeat reQuest. The idea is that ARQ is a method for transmitting data without negative ACKs, so standard ARQ flow is: Sender sends a packet If sender ...
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Error control in Transport Layer vs Data Link Layer

I understand that under the TCP/IP Protocol Suite, error control, flow control and other such services are provided by both, the Transport Layer and the Data Link Layer. My doubt is specific to error ...
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TCP's three-way handshake and Denial of Service attack

Hi I'm a newbie in networking, still confused with the relationship between three-way handshake and Denial of Service attack. As we know that if the client does not send an ACK to complete the third ...
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TCP Fast Retransmit and duplicated acknowledgements Ask

Hi I read an Textbook(Computer Networking : a top-down approach / James F. Kurose, Keith W. Ross.) describes the process of TCP's Fast Retransmit, basically TCP retransmits the lost paclet when it ...
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Send TCP request to closed port, In which layer will the request be discarded

Client send TCP packet to server to a closed port, ie 80. In which layer will the sync packet be discarded? I guess for Client, the request will timeout, for server it should discard the request ...
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Relationship between TCP window size and TCP congestion control

Am I correct that TCP receive window(which is a send window for the sender) has nothing to do with TCP CUBIC congestion control? TCP receive window is solely a property of TCP flow control?
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How is tcp/ip implemented

Well, first of all I am new to networking. And I have studied the layered structure of tcp/ip protocol stack. I know that the layered structure is an abstract model, but I didn't know how the ...
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1answer
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How do data packets travel without merging?

I have been very interested in networking for quite a while, and I have been wondering this question. I've been thinking about this in complete binary, meaning how does a 0 of a data packet not get ...
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Selective Repeat protocol's window size

Hi I'm a newbie to networking, I can understand the differences between Go-Back-N and Selective Repeat protocol on transport layer.I'm confused with Selective Repeat, I know receiver might not be able ...
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Does 1-byte transmission for probe segment operate based on Timeout?

I wonder what ACK number would be if the receive buffer of receiver side is full. For example, Consider a case that sender transmits a segment whose SEQ is 800, and 100 bytes size. Because the receive ...
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Can you vlan tag and assign a priorty (0-7) to SCP traffic

My question is in relation to the file transfer protocol SCP. I have a local time sensitive network built. In time sensitive network you can give priority to traffic by vlan tagging and assigning ...
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Port Numbers related doubt

Assume we have two browsers (Chrome and Firefox) running simultaneously, and both are requesting a web page. Lets assume Chrome is requesting www.facebook.com, and Firefox is requesting www.youtube....
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TCP Vegas: formula for expected number of backlogged packets

While reading Issues in TCP Vegas by Richard J. La, Jean Walrand and Venkat Anantharam (available online here), I stumbled across the following sentence (Part 3 - Rerouting, page 4): When the ...
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Can I run a VPN faster than internet using custom router + optimized protocol other than TCP/IP?

If I make a VPN using a custom, optimized hardware router, running a customized routing protocol much more efficient than TCP/IP, put it in place of the router my ISP gave me, then is it possible to ...
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Simplest explanation of ports, sockets, processes [closed]

Can anyone explain the simplest definition of what ports, sockets and processes are and what is the relationship between all 3. Thanks in advance.
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Is a TCP server limited to 65535 clients?

One might think that this places a hard limit on the number of clients that a single computer/application can maintain. One could be overseeing a web server, and be required to ensure that it can ...
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What is the difference between TCP/IP protocol and TCP model?

We know that there are two models OSI and TCP model. But TCP/IP protocol is different from TCP model as this protocol used in both OSI as well as TCP model. So why the two are named the same is ...
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Does the OSI model support connectionless communication in the transport layer? [closed]

In section 7.4.4.1.2 of ISO/IEC 7498-1:1994(E) it begins with: In connectionless-mode, the Transport Layer provides the following functions to support connectionless-mode transmission: But many ...
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TCP streams/connections

I want to ask how TCP creates streams (and what exactly is a stream). In Wireshark for example, I see multiple streams to one server and I can not understand how/when TCP creates this streams from the ...
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How does the UDP Checksum tell me if my data has changed?

currently I am having a Computer Networking cours and I am reading "Computer Networking a Top-Down Approach" At this point I am reading the Transport Layer part. And I have read about the checksum ...
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Are there any transport layer protocol without the concept of port?

Are there any transport layer protocol that does not have the concept of ports? If so what do they use instead? Also how does NAT work for such protocols?
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Link-state Protocol coverage

During a networking-lecture I was told about the Link-State and Distance Vector protocol. Also we were told about Autonomous Systems and the BGP protocol. Our lecturer told us that with the Link-...
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Why do open ports give no response in networking?

Nmap places ports in open|filtered state when it is unable to determine whether a port is open or filtered. This occurs for scan types in which open ports give no response. The lack of response could ...
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How sliding window protocols handle duplicate packets caused by extreme network delays?

Let's say there is a network that sometimes delivers data with extreme delays. And there is a protocol that uses a "sliding window" algorithm for tracking packets acknowledgement. And imagine such a ...
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What's the difference between port number and protocol number?

Can someone explain it clearly. I know that port numbers are used by applications to differentiate which services you have requested, and routing protocols use protocol numbers in TCP header.
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Is rerouting possible in UDP?

So I am trying to understand routing for TCP and UDP segments. I have a couple of things that I am confused about: In TCP, is there any specification on how many packets would be dropped before a ...
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UDP Sessions and Ephemeral Port Selection

I would like to ask community to help me finding answers to the following questions: According to RFC 6056 an operating system should pseudo-randomly select ephemeral ports for each transport layer ...