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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4
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1answer
4k views

Why do we need master/slave relationship to exchange DBD in OSPF?

I am confused with master and slave relationship in OSPF? Why ospf need the election for master and slave relationship to exchange DBD?
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1answer
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Will hosts do IP Fragmentation?

I heard routers alone do fragmentation. When a host is connected to the network with ethernet cable, how does it keep the MTU size as 1500? Will the host itself fragment and send only 1500 byte ...
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2answers
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Technical difference between a Collision and Broadcast Domain

Many people new to networking wonder what the technical differences between a broadcast domain and a collision domain are. Specifically: What criteria is used to know the boundaries of a collision ...
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2answers
7k views

ARP Replies can they be Broadcast

I have been informed by certain networking professionals that ARP replies can and sometimes actually are broadcast packets instead of unicast. If and when would you use a broadcast ARP reply?
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1answer
237 views

Can we break the Shannon capacity?

I have a friend working in wireless communications research. He told me that we can transmit more than one symbol in a given slot using one frequency (of course we can decode them at the receiver). ...
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4answers
43k views

NACK vs. ACK? When to use one over the other one?

Personally I don't even feel that there is a need for ACK. It's faster if we just send NACK(n) for the lost packets instead of sending an ACK for each received packet. So when/which situations would ...
9
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2answers
59k views

Maximum IPv4 header size

I know the IP header length is a minimum of 20 bytes and a maximum of 60 bytes. But why? Why is the IP header length limited to 60 bytes? Is there anybody here that can explain it to me? Thank you.
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2answers
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Role of SSAP and DSAP in Ethernet DIX frame format

I am well aware of Ethernet DIX format. But, the role of SSAP (Source Service Access Point) and DSAP (Destination Service Access Point) in IEEE802.3 Ethernet frame is confusing and always expressed ...
2
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1answer
375 views

Internet Protocol. Source Routing. RFC 791. Are the addresses in the Source Routing option 1-indexed?

I was reading pages 18-21 in RFC 791 about the Internet Protocol and in the sections on Loose Source and Record Route (LSRR), and Strict Source and Record Route (SSRR), and Record Route (RR) it says ...
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1answer
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Location Request (MT-LR and MO-LR) ASN.1 messages

I am unable to identify the 3GPP specification that gives me message structure in ASN format for MT-LR and MO-LR. Please let me know about this. I browsed through many RRLP, RRC, LTE, LPP documents ...
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2answers
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Implementing the TCP Authentication Option (TCP-AO)

Do any Cisco IOS/XE/XR systems support the updated TCP security option TCP-AO (option kind 29)? It'd be nice to be able to use it. It's defined in RFC 5925, and is meant to obsolete RFC 2385, "...
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3answers
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Reliablity vs unreliable service at IP and Link Layer

I am taking about the 5 layer model. It is well documented that TCP is a reliable service and IP is best-effort delivery and hence unreliable (ref RFC 792 - TCP). Also, the data link layer is '...
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2answers
370 views

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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2answers
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Differences and functions of type codes 0800 and 0806

What are the primary differences and functions (or applications) of type codes 0800 and 0806? Through my own research, I found the 0800 was related to the 0800 to the IP/Layer 3 of the OSI model. ...
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4answers
11k views

How Layer-2 data will be fragmented?

Got a doubt while studying about LLC layer. From Network layer I came to know that IP fragmentation will be done, For L4 TCP will segment the data. Here, the question is Protocols starting from Layer-...
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2answers
2k views

Regarding Route Poison in RIP protocol

I am having a big question regarding Poison reverse concept . Here from the picture The Link between A and T is broken . Now A sends a Triggered update to B and E immediately , and B , E sends the ...
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1answer
835 views

Any reason for rip maximum metric is 15?

I am always getting confused with the statement "Rip protocol maximum diamter is 15" i.e maximum mteric for a route is 15 and metric with 16 is considered as inavlid . Any reason for rip having ...
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3answers
10k views

Why don't switches rewrite mac-addresses?

Is there any particular reason why Ethernet switches don't change the MAC address of a packet? Is it for end host identification using the MAC address, or anything else?
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1answer
3k views

After TCP is established which BGP peer will send open message first?

After a Tcp connection is established between two bgp peers. which peer will send the open message first ? the active peer(which is initiating outbound connection) or the passive peer?(peer which is ...
12
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1answer
24k views

What is the difference between Ethernet II and 802.3 Ethernet?

Can anyone explain to me what is the difference between Ethernet, Ethernet-II and 802.3 Ethernet. I referred to a lot of books, they are in high level language. Can anyone explain to me in a simple ...
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2answers
17k views

Why is the ethernet payload fixed between 46 and 1500 bytes?

Can anyone explain why the ethernet payload size is fixed between 46 and 1500 bytes ? I read so many articles never get the clarification?
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1answer
503 views

What is meant by Jumbo frame ? what happen when a frame size is greater than the MTU size?

I know that the frames having size greater than the MTU size should be dropped . i.e, The Ethernet frame having size more than 1522 should be dropped . But my doubt here is what is Jumbo Frame ?
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1answer
1k views

Why can't we find Ethernet checksum in Wireshark?

I am having a small question regarding Ethernet Frame Header Length. As per my knowledge Ethernet Header size is 18 bytes without VLAN tag and 22 bytes if there is a VLAN tag. But in Wireshark ...
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1answer
377 views

Why do not we have checksum validation in the application Level (BGP , RIP)?

In BGP, TCP handles the checksum and BGP does not perform any checksum validation in the application level. How can we believe TCP must forward the data without errors? Similarly in RIP with UDP ...
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1answer
6k views

Why are there checksums for different OSI layers?

Can anyone clarify the question "why we need checksum in both layer-2 and layer-3 of OSI layer", Layer-2 would encapsulate the rest of OSI layers into a single unit. If Layer-2 has a checksum, ...
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1answer
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Does TCP Cwnd keep increasing if transfer is limited by Rwnd?

I'm trying to understand what happens to the TCP Congestion Window (Cwnd) if the transfer rate is limited by the Receive Window (Rwnd). I know that the transfer rate is the minimum of Rwnd and Cwnd. I ...
33
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2answers
89k views

What is the actual size of an Ethernet MTU

I think I might be getting confused with terminology surrounding MTU. This definition from Wendell Odom's CCNA book on MTU: The IEEE 802.3 specification limits the data portion of the 802.3 frame ...
0
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1answer
721 views

TCP/IP Header compression

I'm reading RFC 1144 and I'm trying to figure out how the TCP/IP header compression works. As I understand it, the sender only sends a couple of fields that are likely to be changed. If the packet ...
6
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1answer
3k views

Wireshark TCP and window size

Can please someone explain me on the below screenshot why host 192.168.1.200 on packet 9 sends an ACK for the packets 6 - 7 - 8? The total packet size does not correspond to the window size agreed. If ...
5
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1answer
511 views

Can 2 peering LSR generate same Label to same or different prefix and distribute among them?

Scope of the MPLS labels are within a router or within a interface right ?. So which means the peering neighbor LSR router can generate label values of its own.So say with below mpls topology. |LSR1|-...
12
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2answers
3k views

Detecting different Ethernet frames

How can someone distinguish between different packets in the Ethernet protocol? It has no "length" field/area as higher-level protocols use to do so. Because this protocol has handling in both the ...
7
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3answers
13k views

What to use as ARP request Target Hardware Address?

When sending ARP request, what must be filled in the target hardware address (THA)? This technet blog post says it is to be filled with zeros (0.0.0.0) -although doesn't look like a MAC address!, and ...
8
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1answer
645 views

Is ADSL's UDP packet forwarding rate strictly linear to packet size?

Suppose an ADSL2 Annex A device had a upload speed of 300kbps; tested using a TCP connection. Now suppose I want to send 8-byte UDP keep-alive packets at the maximum possible rate*. Would the ...
9
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1answer
9k views

What is “1 Erlang” for network data traffic?

I understand (or at least I believe I do) the concept of Erlang load unit when it is applied to voice communications. Voice communications occur in real-time and measured against real-time, so ...
3
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1answer
1k views

Difference between RREQ ID and DestSeqNum in RREQ packet of AODV protocol?

What is the difference between RREQ ID and Destination Sequence number (DestSeqNum) in RREQ packet of AODV protocol? DestSeqNum in RREQ packet is used for a reverse route maintaining and should be ...
13
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4answers
17k views

MTU and Fragmentation

Consider the following: NAS with 10G interface connected to 10G interface on switch. Client computers connected to switch via gigabit Ethernet. Will there be any gain in performance if MTU size is ...
25
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5answers
58k views

Why is 4096 the max value for VLANs

The Tag Protocol Identifier is set to 16 bits. In the CCNA certification it is said that it's not possible to have more than 4096 VLANs. 4096 in binary is 1000000000000000. Since 16 bits are allocated ...
2
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5answers
298 views

Need Clarification Regarding VPN and Routing

I have my topology as follows ... ---------------------- | | | LAN-1 | | (192.168.2.0/24) | | | | | | | -----...
5
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1answer
974 views

IGMP snooping in iptv

Host1 wants to join Multicast group as IGMPv3 include (G,S). The same group and source Host2 send as Exclude(G,S) report. what process done in switch?
4
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2answers
534 views

IGMP snooping (Bridge operation)

What is Meant by RFC 4541 when it says... 4) All non-IPv4 multicast packets should continue to be flooded out to all remaining ports in the forwarding state as per normal IEEE bridging operations.
3
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1answer
822 views

Destination node sequence number increment policy

I read the following from RFC 3561 - AODV, page 11: A destination node increments its own sequence number in two circumstances: - Immediately before a node originates a route discovery, it MUST ...
4
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2answers
4k views

AODV sequence numbers and loop prevention

I am learning about the AODV (ad-hoc on-demand distance vector) protocol. I saw a "sequence number" with a value like "A 46"; however, I don't understand why incrementing this sequence number can ...
5
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3answers
2k views

Importance of encoding data to signal

We all know that there are various encoding schemes to encode data like Manchester Encoding, before sending it. But why is there a need to encode the data to a signal? Why can't we just transmit the ...
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5answers
5k views

Why do we still use Ethernet?

There's no doubt the vast majority of Ethernet frames are transporting IP packets. I know there are various other protocols that can be transported over Ethernet as well, but those can be transported ...
10
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5answers
5k views

Packet sizes in a TCP stream

I'm network traffic and wish to divide each TCP session into a series of requests and responses (the protocols I'm working with all work that way, like HTTP or SSL). I had a simple assumption (...
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4answers
8k views

Can DHCP Server determine client's OS? [closed]

Is it possible for the DHCP Server to determine the client operating system? I'm working on a monitoring tool for gateways on local networks that is web-based and would like to be able to somehow ...
38
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5answers
35k views

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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4answers
17k views

How many TCP/IP layers are involved when I am pinging my router and my PC?

How many TCP/IP layers are involved when I am pinging my router and my PC? My router : ping 192.168.1.1 My PC : ping 127.0.0.1 My PC : Ping 192.168.1.10 I need to know how the data is transferred ...
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4answers
2k views

How can I formulate the communication latency in TCP/IP?

I have difficulty in deriving a mathematical model/equation to estimate the round trip latency between two nodes communicating using TCP/IP. The nodes are exchanging data based on HTTP protocol. In ...

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