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Questions tagged [rfc]

For questions about or involving Request for Comments (RFC), where it is a type of publication from the Internet Engineering Task Force (IETF) and the Internet Society (ISOC), the principal technical development and standardisations for the Internet. For instance, you want to know what a specific RFC means or how you interpret it.

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Suggestion for Weights for Weighted Round Robin

I have looked over the book "End-to-End QoS Network Design" by Tim Szigeti et al. and RFC4594. The RFC proposes 14 Service class: I have a switch with simple QoS features. It has 14 egress queues on ...
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1answer
40 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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21 views

Missing Byte in RFC Packet Notation

In RFC4728 for Dynamic Source Routing (DSR), the route request option is described like this: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 ...
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1answer
42 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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3answers
2k views

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
37 views

Abstract service primitive

In SNMP RFC documents, often the concept of abstract service primitive (ASP) is used. What is ASP in fact ? I think it is also used in ISO OSI.
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0answers
1k views

Cisco BGP Graceful Restart behavior

In our environment we generally have ASR-1000X-2s everywhere peering via iBGP/eBGP. These routers have no redundant RPs, hence cannot keep forwarding traffic while the router reboots or crashes. As ...
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0answers
51 views

Processing received SACK information in case of reordering

I would like to understand how TCP receiver in established state should treat SACK information of out-of-order and fully within receive window segments, where rcv_nxt < seq_no < rvc_nxt + ...
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1answer
79 views

IPv6 source address selection: can the source address have a smaller scope than the destination address?

In RFC 6724 section 5 on "Source Address Selection" rule 2 says to "Prefer appropriate scope": If Scope(SA) < Scope(SB): If Scope(SA) < Scope(D), then prefer SB and otherwise prefer SA. ...
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1answer
49 views

GSM - RFC for GSM protocol [closed]

I'm working on OpenBTS source code and I need to know if there's any RFC documentation out there for GSM protocol to study? I googled it, but there's no specific RFC for GSM protocol itself. ...
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1answer
390 views

Is Per Vlan Spanning Tree or RPVST an open standard or can it only be implemented by Cisco?

I know there are some standards that are CISCO proprietary but have become open standards. CISCO has also updated the RFC to reflect this. So, is this also true for PVST? Does Juniper or other ...
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2answers
228 views

Using a Public AS Number Internally

We have BGP between our network and our customers networks and so far each connection uses private AS numbers (on our end we use a different AS number for each connection) We recently got a public AS ...
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1answer
3k views

What is the practical use of a /31 CIDR or 255.255.255.254?

With a /31 subnet, we are left with zero usable hosts. The /31 subnet only has two hosts - one for network and another for broadcast. I am wondering why would someone ever use this subnet.
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1answer
267 views

What are the component names of CIDR Prefix Notation?

What are the components of the IETF's CIDR Prefix Notation called? 172.16.0.0/16 contains two parts: 172.16.0.0 /16 In the RFC the entire term 172.16.0.0/16 is defined as the "Prefix Notation" for ...
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1answer
168 views

How do ICMP packets travel in a networks?

Questions: I'd like to know how ICMP packets travel in a network? Are they encapsulated within IP datagram? The RFC 792 doesn't explicitly states the layer of ICMP. Are ICMP messages sent using a ...
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1answer
150 views

Class A most significant bits '0' as in RFC1166 or older or '00' as suggested in RFC4632?

I was just reading RFC4632 "2. History and Problem Description" and I don't get the part about Class A with MSB '00'. That would in my understanding mean, there are actually only 64 available networks,...
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2answers
314 views

IPv6 in PPP - should be an Interface Identifier negotiated FOR both ends of a link? Clarification of RFC 5072 needed

I am trying to implement IPv6 in an existing VPN PPP software, but having hard time of understanding some of the RFC 5072 sections meaning. Namely, section 4.1. Assumption 1: PPP interfaces do not ...
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2answers
968 views

What MAC address do I use to generate a IPv6 Pseudo-Random Global ID

I am setting up a virtual lab environment in the cloud to experiment with IPv6 networks. Bear with me please, I'm new to networking and my grasp of the whole IPv6 subject is quite shaky. Please ...
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1answer
456 views

UDP checksum calculation on improperly padded packets

Suppose I'm receiving IPv4 UDP packets whose payload is less than 18 octets, so when they are transmitted over Ethernet they have some trailing padding. Between the packets' source and my receiver ...
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1answer
39 views

What are “Unicast identity tokens”?

I was reading an introduction to IPv6 which talks about the depletion of IPv4 addresses. I came across the following line: As noted in RFC 5735 a number of address blocks are reserved for users ...
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2answers
300 views

Why VPWS service - MPLS has a two ethernet frame headers?

I am trying to understand VPWS services, and going through RFC 4448, Encapsulation Methods for Transport of Ethernet over MPLS Networks. Here is the packet capture: Why there is a need for again ...
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3answers
168 views

VXLAN Protocol introduction

[RFC 7348] about VXLAN in the introduction says: Data centers are often required to host multiple tenants, each with their own isolated network domain. Since it is not economical to realize ...
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1answer
240 views

Does an EIM-NAT work across both UDP and TCP?

I've read RFC 4787, 5382 and 5128 and I just need a bit of clarification. Assume a NAT has Endpoint Independent Mapping behavior for both UDP and TCP. Although I understand that if a machine would ...
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1answer
213 views

What kind of clock is used in tcp timestamps

Most modern computers have atleast 3 to 4 clocks in their motherboards to do different kind of operations. For example in my HP motherboard I got 4 clocks. First One 14.31818Mhz used for CPU and ...
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3answers
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Where can I use the IPv6 documentation prefix

We are currently building a networking course with a practical part where students have to configure a small network in a virtual environment. However, we are not sure what ipv6 prefixes we can use ...
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5answers
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Is “IPv10” a joke or a serious RFC draft?

Internet Protocol version 10 (IPv10) Specification The name is funny (IPv4 + IPv6 == IPv10), but the actual proposal looks strange (one more packet format to battle incompatibility between packet ...
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2answers
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UDP Sessions and Ephemeral Port Selection

I would like to ask community to help me finding answers to the following questions: According to RFC 6056 an operating system should pseudo-randomly select ephemeral ports for each transport layer ...
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1answer
604 views

Where is the maximum packet size for TCP identified as 65,535?

In doing online searches, the value "65,535" is often referenced as the maximum packet size for TCP. Where is this stated? I ask because RFC 793 states, in relation to the "Maximum Segment Size" ...
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1answer
52 views

In inter-domain routing, what methods can I used to specify the set of the ASes that will be traversed?

In RFC 4655, Page 5, the author wrote, "...the path of an inter-AS TE LSP may be computed using a PCE-based path computation model in some ASes, whereas the set of traversed ASes may be specified by ...
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2answers
725 views

How does the ipv4 option “record route” work?

As written in the RFC 791 this option is useful to record the addresses of the routers that an ip datagram goes through. I'm sending an ip datagram with an ICMP echo message, i've set the option type ...
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1answer
113 views

Doubt on handling mutable fields in IP header when computing digest or authentication data

I read RFC 4302, IP Authentication Header, Section 3.3.3, Integrity Check Value Calculation. In page 13, it is mentioned that the fields which are mutable during transit, like TTL or hop count, are ...
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1answer
123 views

“RFC7474 : cross-protocol replay attack”, what is it?

can someone please tell me what the "cross-protocol replay attack for protocols sharing common keys" refers to in the RFC7474? Indeed, in the case of an extern attacker, he does not know any of the ...
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1answer
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Why does Neighbor Discovery Protocol have to monitor upper-layer protocols?

While reading the RFC of NDP I wondered, why it is necessary to monitor upper layer traffic in order to know if a neighbor is reachable, e.g. a TCP ACK. I do get the IPv6 packet anyway, so I know it'...
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1answer
128 views

What does “end site” mean?

I see that many IETF RFC documents use "end site" term. However I cannot find exact definition of an "end site". Does anybody have a reasonable explanation of what is an "end site"? In particular I ...
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1answer
4k views

Why is the minimum MTU of a IPv4 packet 68 bytes?

According to RFC791: Every internet module must be able to forward a datagram of 68 octets without further fragmentation. This is because an internet header may be up to 60 octets, and the minimum ...
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2answers
934 views

How does the TCP/IP stack handle UDP checksum errors?

RFC 2460, Internet Protocol, Version 6 (IPv6) Specification, Section 8.1 Upper-Layer Checksums, states the UDP checksum is mandatory and any IPv6 receivers must discard UDP packets containing a zero ...
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1answer
211 views

Understanding RFC6598 (CGN)

I'm having a discussion with an ISP whether or not we should receive traffic from 100.64.0.0/10 on our firewall. The way I see it we should only receive traffic from their NAT device and not directly ...
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2answers
657 views

Can a subnet mask contain zeros between ones? [duplicate]

In theory, can a subnet mask have zeros between ones (e.g. 255.255.0.248) or it need to be strictly 1's followed by 0's? As stated in RFC 950, there is only an "example" to interpret an IP as <...
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2answers
285 views

Should all sent segments be requeued after a TCP retransmission timeout expires?

I am developing a TCP implementation and could not find a clarification to this in the relevant RFCs (793, 1122, 5681, 6298). When the retransmission timer expires, the first segment which has once ...
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6answers
12k views

IPv4 Segment 100.64.0.0/10

I recently got to know that IP segment 100.64.0.0/10 has been reserved by IANA for 'Shared Address Space'. My question is: Can I use the IP Segment 100.64.0.0/10 as a private range in my network (...
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3answers
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Should a router use SLAAC for IPv6 address assignment?

I am a little confused by the following 2 RFCs relating to IPv6: RFC 4862 (IPv6 Stateless Address Autoconfiguration) RFC 7084 (IPv6 CE Router Requirements) RFC 4862 states: The autoconfiguration ...
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1answer
60 views

sleeping computer on gigabit ethernet kills multicast performance

Problem: any sleeping computer on a gigabit network causes all multicast traffic to drop to 10Mbps. Solution: provide customers with managed gigabit switches and train them to configure the switches ...
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Why is an empty TCP segment at right edge of receive window not acceptable?

The TCPv4 specification (RFC 793) classifies a received segment as unacceptable if it has zero length, a sequence number equal to RCV.NXT+RCV.WND while the receive window is not zero (second row in ...
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2answers
422 views

OSPF Point-To-Point Question

I've consulted the spec https://www.ietf.org/rfc/rfc2328.txt and have googled to the end of the internet but I'm confused on OSPF Point-To-Point. If I have the following: Link State ID: 4.4.4.4 ...
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2answers
343 views

Two IPv6 global unicast addresses on the same interface (stateless and stateful)

Can I assign two global unicast address to the same interface, one obtained via stateful addressing (DHCPv6) and the other one via SLAAC (eui-64)? According to the RFC-4862: Both stateless address ...
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2answers
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BGP RFC https://www.ietf.org/rfc/rfc4271.txt says from Idle a node can go to Active. Wikipedia says it can't

Which one do I trust ? :-) RFC: Idle state: Initially, the BGP peer FSM is in the Idle state. Hereafter, the BGP peer FSM will be shortened to BGP FSM. In this state, BGP ...
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2answers
50 views

Dr election in partial lan connectivity

Suppose we have three routers R1 R2 and R3 with full mesh connectivity in OSPF broadcast network (LAN). R1 becomes DR. R2 BDR and R3 is forming adjacency with both of them. Now let router r4 be ...
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1answer
521 views

For a TCP session, when is the first time an RTT measurement is sampled?

I am trying to understand the RTO mechanism. I have read RFC 6298, but it does not specify when the first RTT measurement is made. Consider the following packet exchange Client -----Syn-----> Server ...
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2answers
3k views

Why are there 3 ranges of private IPv4 addresses?

Why are there three separate ranges of private IPv4 addresses of different sizes? Why not just reserve the largest (10.0.0.0 - 10.255.255.255) range and let people create /16 or /24 (or whatever) ...
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2answers
264 views

IS-IS multi-area

It is well known that an IS-IS L1 router chooses the nearest L1/L2 router to route inter-area traffic, if there is no route leaking as defined in RFC 2966. However, providing that there is no route ...