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Questions tagged [rfc]

A Request for Comments (RFC) is a publication of the Internet Engineering Task Force (IETF) and the Internet Society, the principal technical development and standards-setting bodies for the Internet.

3
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1answer
56 views

Should I reject mail to test domains?

RFC6761 states about example domains (such as example.com): Application software SHOULD NOT recognize example names as special and SHOULD use example names as they would other domain names. ...
3
votes
1answer
62 views

TLS Implementation/RFC interpretation

Does the Server Hello break the RFC? There seems to be contradiction in RFC. A customer claims our device (Citrix Netscaler) returns Extension (ec_point_formats: EC point format: uncompressed) when ...
0
votes
1answer
45 views

Is it possible DNS packet contains more than one SOA resource record

I've read RFC 1034 and RFC 1035 to learn about DNS protocol standards. I'm searching to find a limit occurring of SOA resource records. I'm aware that A, AAAA, CNAME, NS, MX, TXT RRs have no limit. ...
2
votes
0answers
86 views

LDAPS Microsoft Active Directory Multiple Certificates RFC6125

We have an Microsoft Active Directory Domain with a large pool of domain controllers (DC) that are are setup with LDAP. These are all setup with LDAPS and uses Certificate Services via a template to ...
0
votes
0answers
27 views

Is there any IETF / RFC standard defined for hosts file encoding?

While going through the accepted answer for hosts file ignored, how to troubleshoot?, I observed the statement "The hosts file should encoded in ANSI or UTF-8 without BOM". As I personally faced ...
2
votes
1answer
396 views

Which characters/values are allowed to use in DNS?

While I was looking on RFCs of DNS because of implementation to check underscore in CNAME records, I found this interesting discussion and RFC with interesting point: https://www.ietf.org/mail-...
1
vote
1answer
67 views

Which side of this SMTP conversation is correct?

I have an odd scenario with two mail servers communicating with one another and need help determining which one is behaving correctly. It's a little complicated to explain, so I think a SMTP ...
-1
votes
1answer
174 views

Can a non-authoritative name server give any response it likes to?

Our domain registrar allows us to either make use of our own DNS servers or to use theirs (configuring DNS entries in their web interface); I suppose this is a common situation. We have opted to set ...
0
votes
1answer
328 views

Special characters in mail (address) headers and RFC2047 encoding

I have some unexpected handling of RFC2047 "From" headers on Exim. (Actual addresses have been changed, the original display name contained non-ASCII characters) For this "From" header: From: =?iso-...
1
vote
1answer
132 views

Why IPs from the Private Address Space would be reachable through public network, and what customers can do about it?

Scenario: I have a customer running a Win7 Pro and an OpenVPN client; this workstation is used from one of their employees to send remote cmds to the (Windows) OpenVPN server, both using psexec and ...
-1
votes
1answer
6k views

Yahoo Mail: “No mx record found for domain”

Yahoo's Mail servers are refusing to deliver messages to the mail server for a domain I manage. It complains that there is no MX record for the domain. According to my understanding for many years, ...
0
votes
1answer
286 views

Email format RFCs

I know there are lots of RFCs that changed how an email can be made. However, most of the RFCs don't apply to for example outlook. First of all, what are RFCs exactly? And why don't for example ...
1
vote
1answer
3k views

Rejected emails: Messages with multiple addresses in From: header are not accepted - gsmtp

We host a service which can send emails on behalf of client businesses to end users. These emails must appear to be from the client business, even though they are generated from within our system. We ...
0
votes
1answer
57 views

To-Recipient Required in Email?

I would like to know if a "To"-Recipient is required in an e-mail per definition or if all recipients could be Bcc or Cc. RFC5322 states The only required header fields are the origination date ...
3
votes
2answers
70 views

why can the Sender field not be easily configured?

To clarify this and this explanation for Sender:: In brief, From: in the message indicates the mailbox of whoever wrote the message, Sender: indicates the entity which sent a message on behalf ...
14
votes
2answers
1k views

What's the point of repeating an email address in “The Envelope” and the “The Header”?

I learned that both the FROM address and the TO address is repeated in a hidden element called the "envelope", and then repeated again in the "body". Question Why isn't the envelope data copied into ...
1
vote
1answer
56 views

Does a ccTLD/gTLD give out response from cache (or use cache)?

The question is exactly the same as the title says. Does the ccTLD/gTLD (and root servers come into the scenario automatically i presume) use cache? And what type of response it supplies? I know ...
1
vote
1answer
192 views

Debate with Microsoft on RFC 1918 when setting up a VPN to Azure

Microsoft has a technology called "point to site" VPN. (reference1, reference2) I have the following internal class "A" networks defined on premise: 10.2.0.0/16 10.4.0.0/16 10.40.0.0/16 10.20.0.0/...
1
vote
1answer
493 views

What is the format of the NAME field in the DNS answer section?

The NAME field is not detailed completely in RFC 1035 section 4.1.3. I want to understand this field (programmatically) for the ANSWER message type and I searched these resources (datasheet) for that....
4
votes
2answers
4k views

Why isn't net.ipv4.tcp_rfc1337 enabled by default?

The tcp_rfc1337 setting seems to have a solution for TIME-WAIT Assassination. The first problem is that old duplicate data may be accepted erroneously in new connections, leading to the sent data ...
1
vote
1answer
1k views

Creating a RFC 1123 compliant date for HTTP header creation on the CLI

I'm trying to create a HTTP 1/1 compliant date header using standard unix date(1) in order to post this to a RESTful server using curl or similar. Any ideas what format to pass to date(1) to get this ...
0
votes
0answers
38 views

IMAP woes when moving to new Exchange

We've recently moved to a semi-outsourced Exchange farm, replacing our internal one. An application I've been asked to help troubleshoot uses IMAP to download some emails from the Exchange servers in ...
10
votes
2answers
1k views

RFC that requires DNS servers to respond to unknown domain requests

My domain registrar and DNS provide currently ignores DNS requests to unknown domains. By ignore I mean black-holes and never responds which causes my DNS clients and resolver libraries to retry, ...
44
votes
2answers
2k views

Which RFCs should be cited as internet standards?

It's extremely common for RFCs to be cited in support of opinions (including Serverfault Q&A's), but the average IT employee has a very poor understanding in regards to which RFCs define standards ...
1
vote
1answer
552 views

Sendmail support of empty group addresses (AKA list syntax)

E-mail group addresses such as undisclosed-recipients:; or a group:<u1@example.net>,<u@x.example.net>; are valid forms of addressing according to RFC 5322, see for instance the ...
-1
votes
2answers
25 views

Is RFC1035s definition of a <domain-name> wrong?

[RFC1035] defines <domain-name> as <domain-name> is a domain name represented as a series of labels, and terminated by a label with zero length. This means a <domain-name> must be ...
18
votes
2answers
2k views

Why is RFC 7505 (Null MX) necessary?

IETF RFC 7505 describes MX records for a domain/host that explicitly should not receive email. This is accomplished by pointing the MX at the Domain Name System root. For example, nomail.example.com. ...
1
vote
2answers
284 views

Is smart hosting to an A record a violation of RFC-5321 section 1?

I have a sendmail server configured to smarthost to a downstream resource. The configuration is currently: define(`SMART_HOST',`relay:[vip.example.local]')dnl Since it's sending the A record for ...
1
vote
1answer
1k views

ICMP replies - ingress or egress interface (e.g. from a traceroute)

When a traceroute is initiated and receives an ICMP reply from the nodes, which interface should the be replying be from according to RFC 1812. they are actually replying from ingress (where they ...
31
votes
1answer
6k views

How does the DNS protocol switch from UDP to TCP?

Before anyone asks: I've seen When do DNS queries use TCP instead of UDP? and it doesn't answer my question. All I keep hearing is "if the answer is too long, DNS will use TCP". This does not explain ...
1
vote
1answer
429 views

Is Strict-Transport-Security HTTP header name case-sensitive?

I'm digging into the HTTP Strict-Transport-Security specification, https://tools.ietf.org/html/rfc6797 It specifies the syntax of the header like this: Strict-Transport-Security: max-age=15768000 ; ...
1
vote
0answers
216 views

Unable to get structured data in logged messages even after adding mmpstrucdata and mmrfc5424addhmac?(RFC5424)

I am trying to log messages with structured data . But it is showing null value for structured data. I am working with rsyslog 8.9.0.Can someone tell me either i need to load some module or modify ...
-1
votes
1answer
340 views

Apache set max Content-Range

The Question: Client asks for: Range:bytes=0- Server responds with: Content-Length:8396748 Content-Range:bytes 0-8396747/8396748 I want to limit that Content-Range to 1MB chunks so the server ...
3
votes
0answers
2k views

Does a ping to 127.0.0.1 hit the network card? Which RFC / standard states that? [closed]

I recently did an exam where one of the questions stated that you can run ping 127.0.0.1 on a computer to verify if its network card is working. I have already read on multiple sources that this ...
5
votes
3answers
143 views

What to do if one doesn't want to receive email bounces?

Background—the standards RFC 5321 §4.5.5 states: All other types of messages (i.e., any message which is not required by a Standards-Track RFC to have a null reverse-path) SHOULD be sent with ...
4
votes
1answer
1k views

Replacing an MX record with a CNAME that doesn't match the hostname

Today we have 5 companies that all use Google for email services example1.com. 3w IN MX 10 mail.Google.com. example2.com. 3w IN MX 10 mail.Google.com. example3.com....
0
votes
1answer
31 views

RFC5321 “receiver should check […] reply code” (why?)

In SMTP commands are sent by the sender and responses which all begin with a numeric code are sent by the receiver. but then there's this bit: RFC5321 sec4.2 Whenever possible, a receiver- SMTP ...
2
votes
0answers
1k views

Why does RFC 2181 disallow MX record with a CNAME exchange?

According to RFC 2181 http://tools.ietf.org/html/rfc2181#section-10.3 10.3. MX and NS records The domain name used as the value of a NS resource record, or part of the value of a MX ...
0
votes
1answer
215 views

Different throughput Ethernet-Wireless Wireless-Ethernet

I've built an open source implementation of RFC2544 to test IPv4 network devices. One of the first devices I tested is a wireless router D-Link 2640B. In order to measure its performance I use a ...
8
votes
1answer
371 views

Is there an official limit to nameserver indirection?

Glue records are typically unavailable if a domain and its nameserver don't share a TLD, and technically aren't required if they don't share the same second-level domain, which could lead to extra ...
1
vote
1answer
3k views

What does this SAP error mean? recv104 NiIReadrecv nixxi.cp5087

I have an SAP BI Portal system and an SAP BW system. In the Visual Administrator of the BI Portal, section 'JCo RFC Provider' I have created some RFC listeners. In the SAP BW system (in transaction ...
1
vote
1answer
909 views

How to exclude LAN traffic from IPSEC policy

I am trying to replace a Firewall/VPN appliance (Snapgear SG300) with another (Mikrotik RB951G-2HnD). My current router works, but, for the new mikrotik router, when I add the phase 2 tunnel, I can ...
1
vote
0answers
301 views

IPv6 and AdvManagedFlag

RA messages have AdvManagedFlag. If this flag is ON then host "should use stateful autoconfiguration to obtain addresses" (RFC 2462). But RA messages are processing by the kernel. How do we know that ...
8
votes
7answers
1k views

Best choice of private addresses for a “device area network”

I'm building an appliance consisting of several subdevices connected by ethernet inside the appliance. The appliance will connect to the customer network. The customer network can be using private ...
20
votes
2answers
8k views

SMTP allows for multiple FROM addresses in the RFC. Was this ever useful, why does this exist?

SMTP allows for multiple FROM addresses on the body (not the envelope) according to the RFCs. Has this feature ever been used for a legitimate purpose? Is it safe to discard messages that have ...
0
votes
1answer
1k views

Qmail / Zend Mail - RFC 5322 compliant

My company is getting spammed by itself, or rather by it's Qmail, we've got a few automated processes sending out e-mails with Qmail and Zend Mail. I'm not a expert in either of these, (I know ...
4
votes
2answers
145 views

In SMTP, how does one choose between “Accept than Bounce” vs “Bounce at the edge”?

There seems to be a variety of implementations of SMTP that either immediately reject a message, and others that do an accept, then bounce the message. Operationally, the accept-than-bounce is a ...
4
votes
1answer
1k views

What encoding is used for non English languages in an email subject?

I'm writing a specification that essentially requires ASCII characters in an email message. I do recall that an email message can have a subject encoded in a foreign language, however I don't know ...
18
votes
2answers
1k views

RFC 1918 address on open internet?

In trying to diagnose a failover problem with my Cisco ASA 5520 firewalls, I ran a traceroute to www.btfl.com and, much to my surprise, some of the hops came back as RFC 1918 addresses. Just to be ...
16
votes
4answers
37k views

Legitimate reasons SMTP “MAIL FROM:” will not match “From:” Header in DATA

Is there ever a legitimate reason for the SMTP “MAIL FROM:” field to not match the “From:” field in the DATA section of a message, besides mailing lists? From https://stackoverflow.com/questions/...