View source for Classless Inter-Domain Routing (CIDR)

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## Classless Inter-Domain Routing (CIDR)

'''Classless Inter-Domain Routing (CIDR)''' is a networking technique that significantly improved the efficiency of routing on the internet. While seemingly distant from the world of [[binary options trading]], understanding CIDR is crucial for traders operating in automated systems, utilizing Virtual Private Servers (VPS), or analyzing data feeds from various geographical locations. This article will explain CIDR in detail, its history, how it works, and its relevance to the binary options trader.

=== Historical Context: The Rise of IP Addressing and Routing ===

In the early days of the internet, the original IP addressing scheme, known as [[Classful Networking]], divided IP addresses into five classes (A, B, C, D, and E). Each class had a fixed network size. Class A networks were very large, Class B were medium-sized, and Class C were small. This system worked reasonably well when the internet was small. However, as the internet grew exponentially in the 1990s, this system became unsustainable. 

The key problem was IP address exhaustion. The allocation of addresses was inefficient. Organizations were often assigned large blocks of addresses (e.g., a Class B or C network) even if they only needed a small fraction of them. This wasted valuable IP address space. Furthermore, the size of routing tables – the tables routers use to determine the best path for data – grew dramatically, slowing down routing performance. Every router had to store information about every network, even if it didn’t directly connect to it. This scalability issue threatened the future of the internet.

=== Introducing CIDR: A More Efficient Solution ===

CIDR, introduced in 1993, was designed to address these problems. It abandoned the rigid classful network boundaries and introduced a more flexible system based on variable-length subnet masking (VLSM). The fundamental change was the introduction of a new notation for IP addresses:  '''IP address/prefix length'''.

*   '''IP Address:''' The standard IPv4 address, consisting of four octets (numbers between 0 and 255) separated by dots (e.g., 192.168.1.1).
*   '''Prefix Length:''' A number between 0 and 32 that indicates the number of bits in the IP address that represent the network portion.  The remaining bits represent the host portion.

For example, 192.168.1.0/24 represents a network where the first 24 bits (192.168.1) identify the network, and the remaining 8 bits (the last octet, 0-255) identify the hosts within that network.

=== How CIDR Works: Subnet Masking and Address Aggregation ===

The prefix length effectively defines the [[subnet mask]]. The subnet mask is a 32-bit number that, when combined with an IP address using a bitwise AND operation, reveals the network address. 

Let's break down an example:

*   IP Address: 192.168.1.10
*   CIDR Notation: 192.168.1.0/24

The /24 means the subnet mask is 255.255.255.0.  In binary:

*   IP Address: 11000000.10101000.00000001.00001010
*   Subnet Mask: 11111111.11111111.11111111.00000000

Performing a bitwise AND operation results in the network address: 11000000.10101000.00000001.00000000 which is 192.168.1.0.

CIDR’s true power lies in its ability to perform '''address aggregation''', also known as '''supernetting'''.  Instead of advertising individual networks, ISPs can advertise larger blocks of addresses. This drastically reduces the size of routing tables. For example, instead of advertising 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24, an ISP could advertise 192.168.0.0/22, which encompasses all three networks. This significantly simplifies routing and improves performance.

=== CIDR Notation and Network Sizes ===

Here’s a table showing common CIDR notations and the corresponding network and host sizes:

{| class="wikitable"
|+ CIDR Notation | Network Size | Host Size |
|-| /8 | 16,777,216 | 254 |
|-| /16 | 65,536 | 254 |
|-| /24 | 256 | 254 |
|-| /27 | 32 | 30 |
|-| /30 | 4 | 2 |
|}

Note: The host size is calculated by subtracting 2 addresses (the network address and the broadcast address) from the total number of possible host addresses.

=== Relevance to Binary Options Trading ===

While CIDR doesn't directly impact the price of a binary option, it has several critical implications for traders, particularly those engaged in automated trading or relying on external data sources:

1.  '''VPS Selection:''' When choosing a [[Virtual Private Server (VPS)]] for automated trading, understanding CIDR can help you assess the server’s network configuration and potential for reliable connectivity.  A VPS provider with well-managed CIDR blocks is less likely to experience routing issues that could disrupt your trading algorithms.

2.  '''Data Feed Location:''' Many binary options brokers and data providers serve their feeds from specific geographical locations. Knowing the CIDR block associated with these locations can help you optimize your connection for minimal latency.  Proximity to the data source significantly impacts execution speed.  See also [[latency arbitrage]].

3.  '''IP Blocking and Geo-Restrictions:''' Brokers sometimes implement IP-based restrictions to limit access from certain regions or to block potentially fraudulent activity. Understanding CIDR allows you to determine if your IP address falls within a blocked range.

4.  '''Automated Trading Systems:'''  Complex trading systems often rely on multiple external APIs and data feeds. Properly configuring network settings, including CIDR masks, is essential for ensuring seamless communication between these components.

5.  '''Security:'''  Understanding CIDR is crucial for configuring firewalls and access control lists (ACLs) to protect your trading systems from unauthorized access.  You can use CIDR notation to define specific IP address ranges that are allowed or denied access.

6. '''API Integration:''' When integrating with broker APIs, you may need to whitelist specific IP addresses or CIDR blocks to ensure your system can connect.

7. '''Network Monitoring:''' For advanced traders, monitoring network traffic and identifying potential routing issues can provide valuable insights into the performance of their trading systems. CIDR provides a means of efficiently categorizing and analyzing network traffic.

=== Advanced CIDR Concepts ===

*   **Variable Length Subnet Masking (VLSM):**  Allows for the creation of subnets of different sizes within a larger network. This maximizes IP address utilization.
*   **Supernetting (Route Aggregation):** Combining multiple networks into a single, larger network to reduce routing table size.
*   **Classless Inter-Domain Routing (CIDR) Blocks:**  ISPs are assigned blocks of IP addresses based on CIDR notation. These blocks are then further subdivided and allocated to customers.
*   **Route Filters:**  Used to control the flow of routing information and prevent the propagation of invalid or unwanted routes.

=== Tools for Working with CIDR ===

Several online tools and command-line utilities can help you work with CIDR notation:

*   **CIDR Calculators:**  Online tools that allow you to convert between CIDR notation, subnet masks, network addresses, and host ranges. (e.g., [https://www.subnet-calculator.com/](https://www.subnet-calculator.com/))
*   **ipcalc:** A command-line utility for performing CIDR calculations on Linux and macOS systems.
*   **Network Scanners:** Tools like Nmap can be used to scan networks and identify IP address ranges and subnet masks.

=== CIDR and IPv6 ===

While CIDR primarily addresses the limitations of IPv4, the principles of variable-length subnet masking and address aggregation are also applicable to [[IPv6]]. IPv6 has a vastly larger address space, but efficient address allocation and routing are still important.

=== Further Learning ===

*   [[TCP/IP Model]]: The fundamental networking model that underpins the internet.
*   [[Subnetting]]: The process of dividing a network into smaller subnets.
*   [[DNS (Domain Name System)]]: Translates domain names into IP addresses.
*   [[Firewalls]]: Network security devices that control access to your systems.
*   [[Volatility Trading]]: Strategies using price fluctuations.
*   [[Technical Analysis]]: Using patterns for trading.
*   [[Volume Analysis]]: Trading based on trading volume.
*   [[Risk Management]]: Protecting your capital.
*   [[Binary Options Strategies]]: Different trading approaches.
*   [[Broker Selection]]: Choosing a reputable broker.
*   [[Automated Trading]]: Using software for trading.
*   [[Scalping]]: Short-term trading strategies.



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**Обоснование:** CIDR - это концепция, используемая в сетевых технологиях, которая может быть частью обучения в области торговли, особенно высокочастотной торговли или алгоритмической торговли, где понима]]