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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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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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
67 views

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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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
48 views

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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2answers
50 views

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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1answer
59 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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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
343 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
57 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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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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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
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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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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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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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7k 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
77 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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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
55 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
51 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
55 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
222 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
129 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
97 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
109 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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1answer
78 views

STP Convergence: How does a port initially in blocking state know it needs to change to a designated port?

I am attempting to gain a better understanding of how STP converges when certain state changes occur that affect the STP topology. In this scenario (see below) Switch A (SwA) is the root switch with ...
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1answer
132 views

Why do Designated Ports in STP still send BPDUs if the otherside of the link is blocking?

Is there a particular reason for a Designated Port to continue sending out BPDUs after convergence has occurred on a link where the other side is in a STP blocking state? I get the idea of a ...
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1answer
88 views

Confusion about IANA “Protocol Numbers” registery

In the IANA registery for "Protocol Numbers", there listed 2 IP protocol versions: IPv4 at #4 and IPv6 at #41. Their "protocol" column says IPv[46] Encapsulation, and "reference" column points to 2 ...
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2answers
97 views

Which port determines the protocol?

If we have a common protocol port on both ends.. say source point is 443 and destination port is 80 (hypothetical situation, I know this combination of ports probably makes no sense).. how do we ...
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1answer
57 views

Function of the P-bit flag in an IPv6 multicast

Currently I'm trying to learn (common) things about IPv6 and started with the address format and the address scopes. Finally I reached the multicast part where my problem with the definiton of the ...
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2answers
122 views

Is the first address in an IPv6 subnet assignable?

I am working in a lab and have configured a series of /125 subnets between routers. Lets ignore the best practice for this discussion of using /64 for everything. When I assign fd00:f9a8:ffff::257 to ...
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1answer
35 views

OSPF: What's the consequence of two nssa area translator router

If NSSA area has 2 ABR, then usually one of them will be elected to be translator by router id. But what if I have 2 translator routers and both translate the message simultaneously? How to route in ...
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2answers
291 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 ...
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1answer
60 views

Is TCP aware of MAC adress

lets say I would like to make connection between client and server on port 80. Is 3 way handshake aware of server MAC address? I mean: client send SYN data packet to specific IP:port and MAC. In ...
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1answer
64 views

Is there any fixed version of CSMA/CA?

I was trying to understand exact algorithm for Carrier Sense Multiple Access / Collision Avoidance mechanism from Forouzan's book. The book gives very detail explanation of topics. However explanation ...
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2answers
191 views

What is the difference between connect and active states of BGP?

What is the significance of having two different states in FSM when both try to establish TCP Connection?
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1answer
339 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
93 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
54 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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1answer
186 views

Can communication to broadcast 224.0.0.1 be made to reach hosts outside of the local subnet?

I been asked the question if it is possible for an a IP host to use multicast to address 224.0.0.1 in order to reach (and get a response from) another host which is not on the local network segment ...
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1answer
75 views

what are Hardware size and protocol size in ARP header? Attached image

While working on packet capture for a simple scan, just had a look at packet capture and want to know what does hardware size and protocol size means in a ARP header?
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1answer
78 views

When IP header of length 22bytes is there then how padding will work?

My base IPv4 header of 20bytes + 2bytes i used for Options making it 22bytes means 176bits so padding will add 16 Zeroes to make it multiple of 32? is this correct way to understand? Boundary of ...
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1answer
30 views

Why do we need EIGRP AS numbers when we have EIGRP RID?

I understand that the EIGRP routers need to have the same AS number to peer with each other. But why can't we just use EIGRP Router ID?

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