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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23
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7answers
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Does UDP do anything at all?

It's my understanding that TCP has logic for ensuring reliable communication, but UDP just naively sends information along the channel set up for it using IP and things in lower layers. Does UDP ...
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0answers
10 views

How does Router identify RTP packet? [closed]

I am working on a VoIP application and tried to use protobuf for communication instead of a standard RTP packet format. I was reading about VOIP prioritization by routers and I am keen to know how ...
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2answers
42 views

Congestion control in transport and network layers in TCP/IP

Why do we need congestion control in BOTH the transport layer and network layer in TCP/IP model. Cant we be good enough with control in just one of the layers only? And how do they differ?
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2answers
93 views

What will happen if a server receives a duplicate SYN for an existing connection?

If a server receives a fresh SYN packet for a connection that is already established, what should it do? I have already seen What will happen at server side if it received 2 SYN packet from the same ...
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2answers
123 views

Is this UDP diagram wrong?

I was just wondering if anyone can tell me why all UDP diagrams I have seen list a request from the server to the client as the first point of communication? Take a look at the following diagram for ...
0
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1answer
24 views

How do I properly serialize a network packet [closed]

So I'm currently writing a program that is essentially just a server and a client. The idea is that I want them to be able to communicate with one and other by sending packets back and forth. And I'm ...
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2answers
31 views

what's the window size of TCP pipelined sending

We know that instead of send a packet and wait a RTT then send another(stop and wait), TCP use pipelined sending as picture below shows: so my question is, what's the maximum packets can be send in ...
0
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1answer
35 views

Sequence numbers and wrap around concept

I was reading an article about the topic and I came across this :"During connection establishment each party uses a Random number generator to create initial sequence number (ISN), which is ...
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2answers
29 views

how a transport-layer protocol can provide timing guarantees?

I'm reading a textbook which says: A transport-layer protocol can also provide timing guarantees. As with throughput guarantees, timing guarantees can come in many shapes and forms. An example ...
2
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1answer
60 views

Do both sides need to agree on MSS value?

By definition, The TCP Maximum Segment Size (MSS) is the maximum amount of data that a host is willing to accept in a single TCP/IPv4 datagram. And MSS is one of the parameters which is negotiated ...
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2answers
32 views

Two PC on the same LAN, communicating the same Server

Assume that we have 2 pc on the same LAN, local IP of pc1: 192.168.1.5 local IP of pc2: 192.168.1.6 Now suppose that both pc1 and pc2 wants to connect to a server on the internet, we all know that the ...
0
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1answer
63 views

TCP Handshaking Meaning of RST

I am trying to implement TCP handshaking but receive RST instead of ACK: No. Time Source Destination Protocol Length Info 62 24.622012890 192.168.0.147 ...
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2answers
267 views

Prevent TCP sequence prediction attack

Let's say an attacker gets the sequence number between me and my client. Now he continues the conversation with me and has changed the IP address. How do I prevent packages from being sent to ...
0
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1answer
24 views

Why we use IP address in sockets? [closed]

When a server want to create a socket, it will use a combination of its IP address and some well-known port, let us say 80. So, when a segment arrived, both the server IP and port 80 will be used to ...
0
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2answers
32 views

ICMP is a protocol working in the Network Layer. Why does it send few fields of the transport layer while reporting an error?

I was confused if ICMP is a network layer protocol why does it send transport layer fields in its error reporting messages.
0
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1answer
218 views

TCP Checksum Calculation

I recently started with networking and tcp/ip. The RFC 793 document tells the checksum is made of: pseudo header+tcp header+tcp payload+zeroes(if not divisible by 16). So I have to take 16bit ...
4
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1answer
72 views

Which exact bytes are transmitted while TCP zero window probing?

I read the post about TCP zero window probe and it seems that such a probing segments transmit some payload. But I can't figure out which exactly bytes are sent in probing segments? Is it one (or more)...
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2answers
137 views

Can TCP stand for “Transport Control Protocol”

I know it might sound like a silly question, but afaik TCP stands for transmission control protocol. However I found a couple of websites using the term Transport Control Protocol. So I was wondering ...
1
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1answer
47 views

How does triple handshake avoid establishing connection for duplicate packets(coming later down the line)

The idea behind triple handshake seems to be for duplicates to not cause issues. The way I understand it host sends a sequence x to server. Server acknowledges it and sends it's own sequence y. Host ...
1
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1answer
105 views

Do sequence and acknowledgment numbers treat 3-Way Handshake differently?

1- Just as the message ID that is assigned to each message in PAR, the "sequence number" is a means of providing reliability in a transfer of a byte stream. So sequence numbers are assigned to every ...
2
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1answer
68 views

Does UDP perform packet re-ordering at the destination?

User Datagram Protocol is a simpler message-based connectionless protocol. Connectionless protocols do not set up a dedicated end-to-end connection. Communication is achieved by transmitting ...
0
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1answer
81 views

Transport layer segmentation and Ip layer fragmentation [duplicate]

From the OSI Model's point of view: If we already have Ip fragmentation which happen due to the network limitation, why the transport layer provides the segmentation mechanism via TCP protocol? why ...
1
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1answer
72 views

TCP flow control active waiting

To perform flow control between a sender and a receiver during a TCP connection, the receiver includes in each packet to the sender, the size of available space ‘rwnd’ in its receiving buffer. This is ...
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4answers
159 views

How do networks protocols communicate with each other?

We know that before sending information, TCP has to establish a connection with another host. So, does the request from TCP get encapsulated by lower levels of stack protocols or is it just sent ...
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2answers
329 views

Sequence numbers of segments in three way handshakes of TCP connection establishment or termination

I was trying to understand TCP connection establishment and termination steps from Forouzan's book. In third step of three way handshake of connection establishment, it says following The client ...
0
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1answer
22 views

Question on windowing and determing connection speed

Hi i'm just learning computer networks and i have learned about windowing in tcp And my question is does we determine connection speed using windowing? I mean computer know the number of packets and ...
3
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1answer
406 views

When TCP sender window shrinks?

I was learning TCP from Forouzan's book. It explains sender side window as follows: In that it defines size of receiver window as follows: rwnd = receiver buffer size - number of bytes waiting to ...
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1answer
96 views

ports and security

I'm thinking about how the "port" operates for the network connections and tried reading the CCNA cert. guide to understand the details, however, I need to clarify doubts: does occupying all the TCP/...
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1answer
59 views

Finding MSS for a remote connection that uses tunnelling

I'm working on a codebase where we're trying to test network health by verifying if we can ping the remote site having payload = MSS without any packet fragmentation (using -df flag). Typically, for ...
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0answers
44 views

why we need to make the size of our burst 2 times the product of bandwidth and delay? [duplicate]

A textbook which says: The bandwidth-delay product defines the number of bits that can fill the link. This measurement is important if we need to send data in bursts and wait for the acknowledgment ...
0
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1answer
47 views

How is port 80 associated with application port?

I'm new to networking, just a question on port numbers. We know that port 80 is for HTTP. But if I want to access a web application whose web server handles http requests, normally I type below url ...
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1answer
47 views

What's the word of a Transmission Control Protocol port in the Wireshark captured package?

What's the meaning of the dict there? why the port have the paraphrase? you see the Destination port 39578 (39578) do not have.
0
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1answer
107 views

How does browser decide which destination port to use?

Suppose I have a Vanilla machine and this is the first time I am connecting it to Internet. There is no Cache at any level. I access a website through browser by typing example.com (no http//: or ...
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1answer
58 views

How TCP find the correct application?

I am learning how TCP and application communicate with each other. I am not sure if my understanding is correct, I will use below example to illustrate my understanding and want to ask some questions. ...
3
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2answers
64 views

Overload PAT Question

Learning details of NAT PAT. I understand basics wherein the PAT router incorporates a source port to ID the private address computer communicating out on the public address, enabling the public ...
1
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1answer
281 views

Why server cannot send data in TCP three-way handshaking?

In the three-way handshaking, only from the ACK packet we can send data. Why cannot the server send data with SYN-ACK packet? I understated why a client cannot send data to a server (preventing, for ...
2
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3answers
459 views

What's the use of an acknowledgement number without the ACK flag set?

Isn't it redundant if the ACK flag in the header isn't also on? Do you ever mix an acknowledgement with a normal message - send data and acknowledge a message in the same TCP segment? I feel like ...
8
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6answers
4k views

Could IPv6 make NAT / port numbers redundant?

From what I can tell, each process could get its own IP address, with loads of IP's to spare. What would the drawbacks be? Essentially, your host would become a router and each process is a host (in ...
1
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1answer
472 views

TCP Three Way Handshake?

I have the following query about the tcp handshake. To establish a connection the server must send a packet with SYN flag to 1 Then the server replies with a SYN,ACK flag to 1 , and afterwards the ...
2
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1answer
141 views

Why does TCP need segments if the network layer automatically breaks things up into fragments?

I'm trying to better understand the difference between IP fragments and TCP segments (https://www.shubhsblog.com/tech/difference-ip-fragmentation-tcp-segmentation.html) and there's one thing I'm not ...
2
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2answers
190 views

If an old FIN is delivered, will TCP terminate the new connection?

Two programs use a TCP connection (3-way handshake) to open, communicate, terminate the connection and open a new connection. If a FIN message sent to shut down the first connection is duplicated and ...
5
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4answers
5k views

Can anyone explain to me the difference between the PSH and URG flags in TCP segment?

According to me when PSH flag is set, it indicates that data will have to be sent immediately to the wire and on receiving side the data has to be pushed to the application immediately. When URG flag ...
4
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4answers
292 views

WAN encapsulation

I am having some trouble understanding why does a WAN link need encapsulation, such as MPLS or frame relay? Is it merely to encrypt the info from one LAN to another LAN across the internet?
4
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1answer
113 views

Is an RST only segment ever legitimate?

Is a TCP segment with RST but no ACK ever legitimately encountered today? While some kernels emit such an RST when a SYN segment is sent "illegitimately" from themselves (e.g., nmap half-syn, scapy, ...
0
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0answers
21 views

Does Selective Repeat (SR) ARQ protocol, retransmit all currently unacknowledged segments in the window, or just the base?

I've read several conflicting resources, from text books and different slides, where some even seem to contradict themselves through examples. When an SR ARQ packet is lost, and the timer expires is ...
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1answer
202 views

TCP - correlation between ACKs and receive window

EDIT: I think i get it now. So a simple sliding window mechanism basically assumes the correctly received data is processed immediately. Therefore an acknowledgement implies the data was received AND ...
1
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1answer
320 views

TCP or UDP for Stop & Wait / Go Back N

I'm creating server/client classes for "Stop & Wait" and "Go Back N" (variant of sliding window) protocols, though I'm unsure on whether I should pursue TCP or UDP. From my current understanding I ...
2
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1answer
117 views

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 ...
0
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1answer
21 views

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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1answer
673 views

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 ...