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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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Why do I observe a 4-way TCP handshake instead of an expected 3-way when establishing a connection? [duplicate]

I'm doing a simple HTTP GET query on a localhost from curl to a local webserver. After I did a tcpdump I noticed these packets to be sent each time a request is done: 11:11:27.537300 IP 127.0.0.1....
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1answer
246 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 ...
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1answer
38 views

How to handle IPv6 Extension Header Options with action = 01

RFC 8200 section 4.2 states that if a node does not recognize an option type, that node must do some action depending on the 2 higher order bits of the option type. When the higher order bits are 01, ...
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2answers
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Do extension headers in IPv6 increase the header length

I was reading about IPv6. It says the header is of a fixed size i.e. 40 bytes, then how come is it able to accommodate extension headers. Doesn't this alter the size of headers. Please help, cant ...
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2answers
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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 ...
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Why does TCP exit out of slow-start faster than expected?

For context, I am testing a client-server TCP flow, where the client makes a request for a file, and the server sends the file using regular TCP streams. Both servers are using the "Cubic" ...
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1answer
17 views

Understandable/Implementable explanation of CSMA p - persistent

I have been trying to understand how the CSMA P-persistent method works, but haven't been able to understand how it's implemented. I have referred to a few textbooks and other sources, but all of them ...
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4answers
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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?
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0answers
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RPL: questions on routing mechanism

I'm studying RPL and two questions came to my mind: 1: Both in storing and non-storing modes, if a node wants to send a packet to another node via P2P communication paradigm, then how does the ...
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3answers
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Why do all the intermediary routers need to run iBGP without tunneling?

I'm trying to understand the configuration behind iBGP - I understand you can run full mesh to prevent loops, run confederation or route reflectors, if you don't want full mesh, else run tunneling ...
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0answers
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Are MAC command frames in IEEE802.15.4 used in real aplications?

I am reading about MAC command frames in IEEE802.15.4-2006 because I need to understand the relationship between these frames and Mesh Link Establishment (MLE) frames in the Thread Protocol. It seems ...
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2answers
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Does an IP address with host part zero's represent a network, or a network interface in a network?

If the host part of a IPv4 address is all zero (e.g. 192.168.1.0 in a network with mask 255.255.255.0), does the address represent the network, or a network interface in the network? Thanks.
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1answer
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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, ...
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1answer
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2answers
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Why do IPv6 unique local addresses have to have a /48 prefix?

According to RFC 4193, unique local addresses will always have a prefix of FD00::/8.. but according to Wikipedia: The block fd00::/8 is defined for /48 prefixes, formed by setting the forty least-...
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3answers
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Are the IPv6 address space and IPv4 address space completely disjoint?

Tanenbaum's Computer Networks says Finally, IPv4 addresses can be written as a pair of colons and an old dotted decimal number, for example: ::192.31.20.46 Does it mean the IPv4 address space ...
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1answer
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EIGRP unequal load balancing, variance command

Is correct to say that the value inserted in the variance command, lets say the value of "2" on a route that has a cost of, lets say "100", will unequally load balance all routes up to a cost of 200 ? ...
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1answer
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How is SampleRTT measured once every RTT, without measuring every segment?

According to the RFC, SampleRTT is measured once every RTT. My text: Computer Networking: A top-down approach (6ed By: Kurose & Ross) also states, that: Instead of measuring a SampleRTT for ...
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1answer
80 views

EIGRP Auto-summary

One more question about EIGRP, EIGRP auto-summary what is the impact on the network ? i was reading about but it was not clear for me. And why is it a good Cisco practice to be disabled ? I am ...
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1answer
35 views

EIGRP metric claculation

I have a question regarding the EIGRP metric system. so if K1 is the Bandwidth and formula is : (K1 * BW + ((K2 * BW) / (256 - LOAD)) + K3 * DELAY ) * (K5 / (RELIABILITY + K4) Whats is BW and ...
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2answers
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Why is VPN not a protocol?

Is VPN a layer 3 concept? says "VPN is not a protocol". Is VPN an application instead? Why is VPN not a protocol? How can I tell if something is a protocol or not? Thanks.
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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
69 views

Does IEEE 802.11 allow soft-combining?

Out of purely theoretical curiosity, I was wondering whether the IEEE specification for WIFI allows for ARQ with soft-combining. I found a number of publications describing the benefits of soft-...
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2answers
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How does a router know it's received an OLSR message?

So I'm working on my own routing protocol based on a alternative to IP, called ILNP, and I'm having trouble understanding how a router differentiates control packets and data packets for OLSR. The IP ...
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1answer
49 views

What are the five flag bits in OSPF Hello packet that specify optional capabilities?

What are the five flag bits in OSPF Hello packet that specify optional capabilities? This may be a textbook question and probably less important.
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1answer
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“Stop-And-Wait” or “Stop-And-Wait ARQ”?

I was reading about noisy and noiseless channels. Under "noiseless channels", it listed "stop-and-wait", and under "noisy channel", it listed "stop-and-wait ARQ". I was wondering what the difference ...
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1answer
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IPv4 only host on a dual stack environment

I am looking into migrating to IPv6 at my company. Our plan is to dual-stack everything for now, however, we have a couple of local servers that are IPv4 capable only. The rest of our network will be ...
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1answer
123 views

What is max speed of WiFi Direct (P2P)?

I'm looking for information on what kind of speeds theoretically can devices connected through WiFI Direct achieve, assuming all devices support WiFi ac?
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1answer
36 views

Where is the block which caused IPV4 client can not access IPV6 Server

I read many documents which are saying if you are in IPV4 network then you can not access IPV6 network, for example when I was at home I can not access some IPV6 website, such as:ipv6test.google.com. ...
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1answer
40 views

How to extract transfer rates from a beacon frame (or WLAN_BSS_ENTRY)?

How can I extract the transfer rates (actually I only need the maximum value) from a WLAN_BSS_ENTRY structure (obtained by WlanGetNetworkBssList)? The value wlanRateSet (WLAN_RATE_SET) seems pretty ...
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1answer
367 views

Will the packet be dropped when the number of hops equals to default TTL?

From my understanding, the default TTL represents the maximum number of hops allowed such that the packet may reach the host. NTP Documentation Archive: ttl - This option is used only with ...
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1answer
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To what address does ARP reply in the presence of MAC masquerading

The ARP packet has a duplicate of the sender/destination hardware address. Theoretically, you could have a case where a device sent Layer2: From AA:BB:CC:DD:EE:FF To FF:FF:FF:FF:FF:FF Layer3: ARP ...
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1answer
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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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1answer
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Multiaccess link show two Designated Routers in area 0

I have 4 cumulus routers setup 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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1answer
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Do the intermediate nodes learn a MAC address in ARP?

my doubt is about the ARP protocol. I know the procedure: if a host wants to know the MAC address of another sends a broadcast frame and the destination answers with its MAC. However, if an ...
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2answers
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Link Local Address using in NDP (IPv6)

How is using of link local address in NDP. We can discover neighbor by using global address. So why we need link local address in NDP?
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3answers
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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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1answer
58 views

A new version of RIPv2 using different keys for each router

There's a problem in a textbook that is really stumping me. How would you enhance the RIPv2 protocol to provide a (more) secure and scalable schema for distributing the updates? Describe the ...
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1answer
322 views

TCP errors explain

Could anyone explain these errors: TCP ACKed unseen segment TCP Dup ACK TCP Previous segment not captured TCP Out-Of-Order TCP Retransmission
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2answers
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NAT Translation Table Port Number

I had a practice question about a NAT-enabled router with outside address 24.34.112.235 and inside network 192.168.1/24 and three inside hosts .1, .2 and .3. The three hosts all open two connections ...
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2answers
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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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1answer
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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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1answer
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Lost Ethertype in encrypted MACsec frames

MACsec uses an Ethertype of 88E5. This presents an obvious problem when encrypting frames which already have, or should have, another Ethertype. This RedHat blog, for example, states "[MACsec] can ...
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1answer
43 views

Quagga router advertisement messages are wrong after an address change

I have a problem with Quagga OSPFv3 implementation. I have a Mininet topology with a host connected to a router. I assigned an IPv6 address to the router interface. And I enabled IPv6 ...
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0answers
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Simulating TCP/IP Illustrated Test Network [closed]

I just recently bought TCP/IP Illustrated volume 1 first edition for cheap and I see that they reference a test network throughout the book that looks like the following Now I'm not the sharpest tool ...
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1answer
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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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2answers
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What Cisco will discard TTL=1 packets for own interface?

There have been a number of questions about router behaviour with IPv4 packets with TTL=1 and apparently contradictory answers. This question is not about what should a host or router do, it is a ...
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1answer
93 views

Why is retransmission delayed when the RTO is long?

I am new to networking and learning about TCP Timer Management and read this in my textbook: "If the value of time-out (RTO) is too small then unnecessary re-transmission will take place. If time-out ...
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1answer
47 views

Why are the Address and Control fields constant in PPP protocol?

I saw that address and control fields are constant in PPP protocol. What is the need for even having a field that has constant value in it if we had not have this field then wouldn't it have saved ...
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2answers
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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 ...