Tag: ip

DNS over TCP

April 23, 2023 / Jordan / 0 Comments

We recently ran into a problem where a DNS query was failing because the response was too large. The maximum size of a DNS response that can be sent over UDP (User Datagram Protocol) is 512 bytes. This is because the original DNS protocol was designed to fit within a single UDP datagram of this size. However, modern DNS implementations often support an extension called EDNS0 (Extension Mechanisms for DNS 0) that allows for larger DNS messages. The problem that we ran into was that our platform didn’t support DNS over TCP!

If a DNS response exceeds the 512-byte limit, the DNS server will set the “truncated” (TC) bit in the response message header and indicate that the client should retry the request using TCP (Transmission Control Protocol). TCP is a reliable, connection-oriented protocol that can handle larger data payloads than UDP.

In practice, most DNS queries and responses fit within the 512-byte limit, and TCP is rarely used for DNS traffic. However, certain DNS applications, such as DNSSEC (DNS Security Extensions) and large DNS zone transfers, may require the use of TCP due to the size of the response data.

Types of DNS records

April 11, 2023 / Jordan / 0 Comments

There are several types of DNS (Domain Name System) records, each serving a different purpose. Here are some of the most common types:

A (Address) Record: This record maps a domain name to an IPv4 address.
AAAA (IPv6 Address) Record: This record maps a domain name to an IPv6 address.
CNAME (Canonical Name) Record: This record creates an alias for an existing domain name, allowing it to be accessed under a different name.
MX (Mail Exchange) Record: This record specifies the mail server responsible for accepting email messages for a particular domain.
TXT (Text) Record: This record allows for the addition of arbitrary text to a domain name. It is often used for domain verification, spam prevention, and other administrative purposes.
NS (Name Server) Record: This record identifies the authoritative name servers for a particular domain.
SRV (Service) Record: This record specifies the location of a service, such as a SIP or XMPP server, on a domain.
SOA (Start of Authority) Record: This record provides information about the domain name, such as the primary name server, the email address of the domain administrator, and the domain’s serial number.

These records are essential for the functioning of the DNS system and are used by various internet services to provide functionality such as email delivery, web browsing, and other network communication protocols.

CIDR Notation

April 1, 2023 / Jordan / 0 Comments

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and subnet mask. It is used to express the number of bits that make up the network portion of the IP address. CIDR notation is written using a forward slash (/) followed by the number of bits in the network portion of the address. For example, a CIDR notation of /24 means that the first 24 bits of the IP address are the network portion, and the remaining bits are the host portion.

There are several common CIDR subnet notations, each of which represents a different range of IP addresses:

/32: This notation represents a single IPv4 address. It is often used to specify a particular host on a network.

/24: This notation represents a Class C network with 256 addresses. It is often used in small-to-medium-sized networks.

/16: This notation represents a Class B network with 65,536 addresses. It is often used in larger networks.

/8: This notation represents a Class A network with 16,777,216 addresses. It is typically used for very large networks.

/0: This notation represents the entire IPv4 address space. It is rarely used in practice, as it allows any IP address to be used.

CIDR notation is also used for IPv6 addresses. The same principles apply, but the notation uses a colon instead of a period to separate the parts of the address. For example, a CIDR notation of /64 means that the first 64 bits of the IPv6 address are the network portion. IPv6 addresses typically use larger subnet sizes than IPv4 addresses, as the address space is much larger.

What is the difference between IPv4 and IPv6?

March 15, 2023 / Jordan / 0 Comments

IPv4 (Internet Protocol version 4) and IPv6 (Internet Protocol version 6) are two different versions of the Internet Protocol used to identify devices on a network. Here are some of the key differences between IPv4 and IPv6:

Address size: IPv4 uses 32-bit addresses, which allows for about 4.3 billion unique addresses. IPv6 uses 128-bit addresses, which allows for a virtually unlimited number of unique addresses.
Address format: IPv4 addresses are typically written in dotted decimal notation (e.g., 192.168.1.1). IPv6 addresses are written in hexadecimal notation and use colons to separate the different segments (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).
Address allocation: IPv4 addresses are allocated to organizations in large blocks, which can lead to address space fragmentation and inefficient use of resources. IPv6 addresses are allocated in much larger blocks, which helps to prevent fragmentation and ensures more efficient use of address space.
Header size: IPv6 headers are larger than IPv4 headers, which allows for more advanced features and better security.
Security: IPv6 includes features such as IPsec (Internet Protocol Security) as a standard part of the protocol, while IPv4 requires additional configurations for secure communication.

Overall, IPv6 was designed to address the limitations of IPv4, particularly with regard to address space, and to provide a more efficient, scalable, and secure protocol for the future of the Internet. However, the adoption of IPv6 has been slow due to the significant effort required to transition to the new protocol.

What is RWHOIS?

March 1, 2023 / Jordan / 0 Comments

rwhois (also known as Referral Whois) is a protocol used to obtain registration information about IP addresses and other Internet resources. It is a distributed database system that allows network administrators to query multiple databases to obtain information about an IP address or domain name. rwhois is similar to the traditional Whois protocol, but it allows for greater flexibility in managing large and complex networks. It enables the delegation of the management of network resources to other organizations, allowing for more efficient use of resources and better management of network security. rwhois servers are typically operated by Internet service providers (ISPs), regional registries, or other organizations that manage large IP address blocks. They maintain information about IP address assignments, network topology, and other important network information. Overall, rwhois is an important tool for network administrators who need to manage large and complex networks. It provides a way to quickly obtain information about network resources, enabling faster troubleshooting and more efficient resource management.