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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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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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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Is a DHCP offer packet a broadcast or unicast?

DHCP OFFER is a layer3 broadcast because the server don't know client Ip, but server knows the client mac address. So how it would be the broadcast? If anyone ask me about this? how should I answer? ...
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1answer
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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
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Which part of IP header indicate net mask?

In IP header , Only the destination ip address and source ip address is indicated . How does a traveling packet know the network section of destination ip address in CIDR notation ? Thanks
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1answer
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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
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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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4answers
133 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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1answer
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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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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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Why is the U/L bit inversed in EUI64?

This inversion is bijective, so I can't figure out what is it's use.
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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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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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4answers
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The reason why TCP sends consecutive ACKs all together

While analyzing Wireshark capturing, I noticed that the sender or the receiver sometimes sends a bunch of consecutive ACKs together as oppose to what I have learned. I learned that for every packet ...
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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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Question on ARP

Given the above diagram, is it correct to say that the ARP cache table in PC A contains the IP-MAC addresses for PC B and the router, while the ARP cache table in PC B contains the IP-MAC addresses ...
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4answers
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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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2answers
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What is the election process of Router ID in OSPF?

I am a little confused on the process OSPF uses to select the Router ID. Is following correct for the selection of the router ID in OSPF? Manual configuration Highest IP address on a loopback ...
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1answer
68 views

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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3answers
3k views

TCP - Urgent flag, when is it needed?

I understand the meaning of this field, and how it is used. But I can't find an example for when it is needed, I read that it is used in Telnet, why? When do I need this flag?
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0answers
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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
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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
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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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1answer
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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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2answers
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What are the differences between tunneling and regular encapsulation?

What are the difference between tunneling (https://en.wikipedia.org/wiki/Tunneling_protocol) and regular encapsulation (e.g. TCP/UDP over IP, HTTP/SSH over TCP)? Is TCP/UDP over IP considered ...
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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
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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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5answers
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Why was the MTU size for ethernet frames calculated as 1500 bytes?

Is there any specific calculation that that was done to arrive at this number, and what were the factors that were taken into consideration for that calculation.
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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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9answers
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Why do we need a 3-way handshake? Why not just 2-way?

The TCP 3-way handshake works like this: Client ------SYN-----> Server Client <---ACK/SYN---- Server Client ------ACK-----> Server Why not just this? Client ------SYN-----> Server ...
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2answers
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What is the benefit of sending some data uncoded in a 10GBASE-T PHY frame?

For 10GBASE-T / IEEE 802.3ae the Physical Coding Sublayer is extended with a low-density parity-check (LDPC) code. IEEE 802.3™-2012 55.1.3.1 Physical Coding Sublayer (PCS): The 3259 bits are ...
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1answer
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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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1answer
44 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 ...
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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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1answer
82 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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0answers
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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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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
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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
245 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
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Why is the Ethernet Connection Symmetric?

I know that cable connection (DSL) is asymmetric, there is a certain bandwidth on the channel, and for a better user experience, they allocate a bigger portion to the downstream. I suppose Ethernet ...
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2answers
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What is the reason for the different order of the Source and Destination in a L2 header?

A TCP/UDP header (Layer 4) lists the Source Port, then the Destination Port: An IP header (Layer 3) lists the Source IP, then the Destination IP: An Ethernet header (L2) and a WiFi Header (L2) lists ...
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1answer
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Why Internet protocol is divided in rows?

In simple words, why IP packet is divided in rows each one is 32 bit in length? For example this attached image shows the IP packet has 32 bit in the first row then another 32 bit and so on. Is it ...
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3answers
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Which first eight bytes of the IP datagram are included in ICMP message?

The definition of ICMP message says that it has a type, a code and the first 8 bytes of IP datagram causing error. Question: Which first eight bytes of IP datagram are included in the ICMP datagram? ...
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1answer
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Multiaccess link shows two Designated Routers in Area 0

I have four Cumulus routers set up with a single ethernet connection from r3 -> r1 -> r2 - r4. From r1, show ip ospf neighbor displays the following: **Neighbor ID Pri State Dead Time ...
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2answers
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Why the first octet of a MAC address always end with a binary 0?

I stumbled upon a piece of code on GitHub: https://github.com/adeverteuil/bash-ula-generator/blob/master/gen-ula.sh # Generate an EUI64 from the MAC address # as described in RFC 3513 # https://tools....
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2answers
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How to advertise a classless network in RIPv2?

In OSPF and EIGRP we can advertise specific networks only using wildcard masks. For example, if a router has networks 10.0.10.0/24 and 10.0.20.0/24, we can choose to advertise only 10.0.10.0/24 by ...

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