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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87 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
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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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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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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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1answer
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Which IPv4 options must be copied on fragmentation and why?

In RFC 791 page 14 it says The copied flag indicates that this option is copied into all fragments on fragmentation. 0 = not copied 1 = copied If I understand correctly it is possible ...
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1answer
143 views

How to understand the Flags is IP_MF, what will happen?

For data packets whose length exceeds the MTU of the interface, fragmentation processing is required. The fields related to fragmentation in the IP header are as follows: Identification - Used to ...
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1answer
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Connectivity problems in a topology [closed]

I cannot identify any network problems in the following topology. https://i.imgur.com/eyUEzvz.jpg Any help in identifying problems would be appreciated, and I would be happy to work on them.
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1answer
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Scaling fragment offset

I studied that fragment offset has 13 bits. At transport layer segmentation is done considering the the MTU at lower layers (network layer, data link layer). Ethernet format says the maximum data ...
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1answer
82 views

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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1answer
141 views

Is OSPF router ID unique per area?

I found online that the router ID must be unique within the OSPF domain. But what exactly is an OSPF domain (an area?). Let's take the following topology: Can R1 and R5 have the same router ID, as ...
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3answers
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How to do subnetting on IPV6 for non nibble boundaries?

As I was reading this article on How to: calculating IPv6 subnets outside the nibble boundary https://blog.apnic.net/2018/08/10/how-to-calculating-ipv6-subnets-outside-the-nibble-boundary/ The author ...
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1answer
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Remote Host Neighbor Cache Entry State after Neighbor Solicitation request

When a Host A sends for the first time a NS request to another Host B, host B answers with a NA. In Host A Neighbor Cache, the state Entry for host B gets from INCOMPLETE to REACHABLE, when NA comes ...
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1answer
257 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 ...
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1answer
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What are the practical applications of Stop & Wait, Selective Repeat and Go Back N?

What are the practical applications when to use Stop and Wait, Selective Repeat, and Go Back N? What in real life protocols are implemented using these mechanisms?
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3answers
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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 ...
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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 ...
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1answer
450 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
47 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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3answers
103 views

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
187 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 ...
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0answers
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Why does TCP exit out of slow-start faster than expected? [closed]

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
24 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
287 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?
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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
230 views

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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2answers
221 views

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
100 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, ...
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1answer
179 views

IHL(Internet Header Length) field is 4 bit long and specifies the header length in 32 bit words. What does it mean?

I am trying to understand IPv4. I cannot understand
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2answers
1k views

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
1k views

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
211 views

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
148 views

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
98 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
76 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
100 views

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
494 views

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
222 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
51 views

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
2k 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
52 views

“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
61 views

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
330 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
64 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
63 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
676 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
149 views

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
57 views

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
33 views

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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1answer
66 views

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
646 views

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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