Questions tagged [protocol-theory]

For questions about network protocols published in a Standard or RFC. Do not use this tag merely because the question mentions a networking protocol in it. Questions with this tag *could* be closed if they do not explain why the question is relevant and important to answer; this is necessary to avoid issues with tangential / trivial questions or help vampires.

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Does an application implemented using services of layer n necessarily belong to layer n+1 and implement a protocol in layer n+1?

I was wondering what counts a protocol? When an arbitrary (software or hardware) application is implemented on top of the service of layer n in the Internet Protocol stack or the OSI model, does ...
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How many time can a Block Acknowledgement Request can be sent if no BA is received, in 802.11 networks?

If we consider a 802.11 ac network, how many time, at most, can a Block Acknowledgement Request be retransmitted if it is not received at first? I'm running simulations in the ns-3 simulator, and I ...
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Does the control packets flow into a router/switch through forwarding plane? [duplicate]

I know there are two platforms in any networking device separating the control packets from the traffic, which I call control plane and data plane. My question is, how does the control packets enter ...
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39 views

Networks theory: Layers, Services and Interfaces

I want to learn about computer networks from the bottom up. I don't really understand the nuances of networking layers, with books mentioning that layers provide services to layers above them, but the ...
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1answer
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Does the first TCP FIN packet (active close) goes with just only FIN bit set?

Suppose we have established TCP connection. The active close process assumes the FIN packet been sent to trigger TCP connection closing. But I can't figure out, is this first (active close) FIN packet ...
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Is there any other network protocol than tcp/udp that works with ports?

Do you know at least one protocol (any OSI layer) that, like tcp and udp, works with ports ? Thank you
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Question about the rebooting state of the DHCP protocol [closed]

Taking into account this diagram... I wonder if a device, after a reboot having a previous known configuration, uses it from the start even tho it's still asking to check if it can continue using ...
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1answer
40 views

Why is delayed segment prevention (TIME_WAIT) in TCP only done for one side?

One of the reasons for TIME_WAIT is to prevent old packets/duplicates, coming in late, to screw up subsequent connections on the same (src ip, src port, dst ip, dst port) quadruplet. That makes sense, ...
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ICMP distinguish error messages

Can a Internet Control Message Protocol when an error is sent can it tell which datagram that made the error?
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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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2answers
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How does the ARP table know to update if two hosts flop IP addreses?

When hosts on the same local network communicate, they manage their own ARP tables which translate between IP addresses and MAC addresses. Thus when computer A needs to send data to IP address ...
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ARP Router issue

I have a question when a Router receives ARP request to a host that dosen't exists on the forwarding table for that router does the. And this Router is not the next hop either will the Router continue ...
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2answers
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MAC address and unicast, multicast and broadcast

I'm very new to computer networking and I'm trying to figure out this dilemma about the Unicast, Multicast and Broadcast transmissions. I was told that MAC address are unique for each device and they ...
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What if my data contains nothing but Preambles and Start of Frame numbers?

Will that continually reset the receiving NIC or is there a sort of escape character that need to be used if my data contains nothing but alternating 1s and 0s in 7 byte blocks with start of frame ...
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2answers
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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
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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 ...
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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 ...
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1answer
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What are usecases for IPv6 link-scope anycast?

IPv6 Neighbor Advertisement messages have a flag called Override, see RFC4861. It toggles, whether the receiver of the message should remove other link-layer addresses for the same IPv6 target address ...
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1answer
94 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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119 views

Network Protocol vs Framework?

I've been a network engineer for almost 4 years now. I thought I understand what a network protocol means. but now I'm having doubts. For me, Ethernet is a protocol used at layer 2. there would be ...
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1answer
37 views

Why do hops before VPN server not reflect in traceroute?

I'm using a remote-site VPN (ProtoVPN). When I tracert to the IP address of the VPN server, the hops through my ISP and other intermediate hops before the VPN sever are shown. But when I tracert to ...
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How does mesh network handles seamless roaming?

When extending a WMN to a city-wide scale one of the problem it faces is seamless handoff. So, do I need to implement one of the ticket based authentication for it to work seamlessly or will IEEE 802....
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1answer
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what were the classless routing protocols used with VLSM when it was first introduced?

Since VSLM is supported only by classless routing protocols, if VSLM was introduced in 1987(RFC 1009) and all classless protocol(RIPv2 developed in 1993 , OSPF standardized in 1989 RFC 1131 ) cited ...
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1answer
109 views

How is the PPP protocol byte-oriented as well as bit-oriented?

Many articles considered PPP as a byte-oriented, and the others mention it as a bit-oriented. +----------+----------+----------+----------+------------ | Flag | Address | Control | ...
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1answer
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IPv6 SLAAC and Static DAD

I started learning about IPv6 and I wonder what happens when you mix SLAAC and static addresses in the same /64. My current understanding is as follows: Machine A with a statically configured ...
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2answers
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Why does Ethernet use EtherType field to determine what type of packet is in a frame instead of just looking at the packet header?

I'm studying for some networking concepts and have learned that a receiving host looks at an Ethernet frame's header to determine what protocol being used by the packet. It makes me wonder though, ...
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1answer
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IPv4 maximum datagram size

The IPv4 datagram consists of two parts:the header length and the payload. The maximum header size is 60 bytes and minimum is 20 bytes. The maximum size of the data can be 65515 bytes. So why the ...
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Why do i see only UDP and not QUIC during capture in wireshark? [duplicate]

During packet sniffing in wireshark i dont see any QUIC or GQUIC packets only UDP
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1answer
350 views

Is TCP slow start supposed to be enabled for VoIP SIP?

TCP slow start mechanism generally is pretty useful in most cases. But it is not so good and reasonable for short-lived TCP connections. Hence the question: Should TCP slow start be used with SIP-over-...
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1answer
59 views

Unexpected bytes in AS_PATH BGP attribute

I am parsing out the ASNs from several AS_PATHS. A majority of the attributes I encounter look like this one: [64, 1, 1, 0, 64, 2, 10, 2, 2, 0, 0, 23, 169, 0, 0, 50, 156, 64, 3, 4, 200, 40, 162, 202]...
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1answer
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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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1answer
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Why must host A continue to transmit after host b sends runt frame post collision on ethernet? (CSMA/CD)

Trying to understand example from computer networks: a systems approach ... -Host A sends Host B a frame at time t; Packet arrives at B at time t + d; (d = one link latency) Instant before frame ...
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1answer
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Do DR-Other router forwards Type 2 LSA received by DR?

In the Diagram below when R1 is newly added to Network Topology R1 and R2 become neighbors and exchange Type 1 LSA from R2, R3, R4. But how R1 knows Network LSA created by the DR in LAN(subnet 1). ...
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1answer
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How can MLDv2 work according to the RFCs 3810 and 4606?

When IPv6 Stateless Address Autoconfiguration is happening, an interface/node has to join the all-nodes multicast address and the solicited-node multicast address AFTER forming a "tentative" ...
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1answer
1k views

Worst-case efficiency of PPP escaping mechanism

Will transferring over PPP data stream containing only reserved bytes 0x7E, 0xFF, 0x03 reduce bandwidth by 50% because of escaping? Then it seems to be very stupid if not say moronic. Such poor ...
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4answers
3k views

Difference between :: and ::1

I am confused about following netstat output. There are two kind of local ports. The first is: [::]8100 The second is: [::1]8100 I know that [::1] is a loopback address for IPv6. My question is: ...
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1answer
49 views

in 802.11, when must a station go to the “random fall back slot” mechanism?

i've been reading Michael Gast's 2005 book on 802.11, and he talks about how each station, after it has seized a channel and finished transmitting, will then have its NAV timer expire (along with all ...
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3answers
9k views

Why does the IPv6 header not include a checksum?

It is stated in Wikipedia that an IPv6 header does not include a checksum. What are the reasons that were behind this decision?
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1answer
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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 ...
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1answer
127 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 ...
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802.11 vs MACA protocol RTS/CTS [duplicate]

im in serious doubts about how diferent are the 802.11 and the MACA protocols I can´t find a simple explanation on the internet on how these are different when it comes to their RTS/CTS parts. Are ...
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3answers
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Why can a host with a single NIC and on two networks have 2 IP adresses?

I understand that an IP adress refers to a NIC and not to a host, therefore a single host can have as many IP adresses as NICs. But Tannenbaum says: It really refers to a network interface, so if ...
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6answers
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What happens with a ping when it enters a network? Is the router the one answering with a reply?

What happens with a ping when it enters a network? Does the router redirects it to one of the devices on the network, or it sends the reply itself? Device a1 from network A, with public IP adress P1 ...
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2answers
60 views

What is VRRP used for?

I want to understand VRRP, but most resources online use complex examples that are fairly hard to understand. I want to understand the big picture. What problem does VRRP(Virtual Router Redundancy ...
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1answer
52 views

What will be the behaviour of TCP in a case when application layer is changed to send small packets

Assume I have an application layer protocol that segments the packet itself. So if it has 100 MBytes of data, then it will divide the data into 10000 segments and send each segment individually to TCP....
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1answer
56 views

Routing protocol comparisons (with Linux) [closed]

I am doing some thesis about comparison of routing protocols, most notably how (how good, how fast) they react to changes in the underlying network. Not sure if this makes any sense, but too late to ...
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3answers
360 views

Why is DHCP client able to accept DHCP Offer packet?

I am seeing a DHCP packet flow, which consists of at least 4 packets: Discovery Offer Request ACK With the discovery packet, client tries to find DHCP server. Since client does not know his own IP ...
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4answers
167 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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4answers
124 views

Why not put unicast address in IPv6 packet containing NDP neighbor solicitation instead of solicited-node multicast address?

This is a follow-up question to Why is the NDP Neighbor Solicitation message sent to the solicited-node address?. Summary: say I would send an IPv6 packet and put the unicast address of the host I ...
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1answer
134 views

Why Do We Use STP (Spanning Tree Protocol) or RSTP (Rapid Spanning Tree Protocol) When Packets are Not Routed Optimally?

I am new to networking so this probably a naive question. I've been reading up on the spanning tree protocol and understand why it's necessary in a network (it prevents loops) and I understand that ...

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