TCP Sliding Window: Purpose & Beginner's Guide

Transmission Control Protocol (TCP), a core protocol of the Internet protocol suite, ensures reliable data delivery between applications. Efficient data management is handled by TCP's sliding window, and its operation is crucial for network performance. The **purpose of the TCP sliding window** is primarily to control the flow of data, preventing a fast sender from overwhelming a slow receiver. Wireshark, a popular network protocol analyzer, allows administrators to observe the sliding window mechanism in action, providing insights into how TCP manages data flow and acknowledges received packets. Network congestion, a common issue, is effectively managed through adjustments to the window size, optimizing throughput without causing data loss.

At the heart of the internet's ability to seamlessly deliver everything from cat videos to critical financial transactions lies the Transmission Control Protocol, or TCP. This protocol acts as the unsung hero, ensuring that the data you send and receive arrives intact and in the correct order.

TCP's importance stems from the inherent nature of the Internet Protocol (IP), the foundation upon which the internet is built. While IP excels at efficiently routing data packets across vast networks, it does not guarantee delivery or the order in which those packets arrive.

The Inherent Unreliability of IP

IP's design focuses on speed and adaptability. Packets may take different routes to their destination, and some may even be lost along the way. This "best-effort" delivery system works well for real-time applications where occasional data loss is acceptable.

But it falls short when reliability is paramount. Imagine downloading a software update where a few corrupted packets could render the entire file unusable. This is where TCP steps in.

TCP: Adding Reliability to the Internet

TCP sits atop IP, providing a layer of reliability that transforms the internet from a potentially chaotic data stream into a dependable communication network.

It achieves this reliability through a series of mechanisms, including error detection, retransmission of lost packets, and ordering of data segments.

TCP and IP: A Symbiotic Relationship

TCP and IP work in tandem, forming the backbone of most internet applications. IP provides the addressing and routing, while TCP ensures the reliable transport of data between applications.

TCP essentially turns IP's "best-effort" delivery into a guaranteed, ordered stream of data.

This crucial feature enables applications to function reliably, regardless of the underlying network conditions. TCP handles the complexities of network communication, allowing applications to focus on their core functionality. The magic of TCP is what makes the Internet as useful as it is today.

Unveiling the TCP Sliding Window: A Dynamic Approach to Data Transfer

At the heart of the internet's ability to seamlessly deliver everything from cat videos to critical financial transactions lies the Transmission Control Protocol, or TCP. This protocol acts as the unsung hero, ensuring that the data you send and receive arrives intact and in the correct order.

TCP's importance stems from the inherent nature of the internet itself. Packets can be lost, duplicated, or arrive out of order due to the decentralized nature of IP routing. This is where the TCP sliding window mechanism comes into play.

The TCP sliding window is a dynamic, sophisticated mechanism that provides both flow control and reliable data transfer. It's not a static entity, but rather a constantly adjusting window of data that the sender is permitted to transmit. Understanding this window is crucial to understanding how TCP achieves its reliability guarantees.

Defining the Sliding Window

Imagine a pipeline through which data flows. The sliding window defines how much data can be "in flight" at any given moment, without overwhelming the receiver. It's a dynamic agreement between sender and receiver about the amount of unacknowledged data that is allowed. This window "slides" forward as data is acknowledged, permitting the transmission of new data.

The Three Pillars of the Sliding Window

The sliding window fulfills three primary purposes that are essential for reliable communication: preventing receiver overload, enabling efficient data transmission, and ensuring reliable data delivery.

Preventing Receiver Overload: A Matter of Capacity

One of the most important functions of the sliding window is to prevent the receiver from being overwhelmed with data. Each receiver has a finite amount of buffer space and processing power. The sliding window allows the receiver to dynamically advertise its capacity to the sender.

If the receiver is busy, it can shrink the window size, signaling to the sender to slow down the transmission rate. This dynamic adjustment ensures that the receiver never gets more data than it can handle.

Efficient Data Transmission: Sending Without Waiting

Waiting for an acknowledgment (ACK) for every single packet would be incredibly inefficient. The sliding window allows the sender to transmit multiple segments of data without waiting for individual ACKs. The window size determines how many segments can be "in flight" simultaneously.

This parallel transmission dramatically increases efficiency and throughput. The sender continues sending data until the window is full, at which point it waits for ACKs to open up the window again.

Reliable Data Delivery: Order and Loss Prevention

The sliding window works in conjunction with sequence numbers to ensure reliable data delivery. Each segment of data is assigned a unique sequence number. The receiver uses these sequence numbers to reassemble the data stream in the correct order, even if segments arrive out of sequence.

Furthermore, the sliding window enables the detection and retransmission of lost packets. If an acknowledgment for a particular segment is not received within a reasonable time, the sender assumes the segment was lost and retransmits it. This ensures lossless data reception.

Anatomy of the Sliding Window: Key Components and Mechanisms

[Unveiling the TCP Sliding Window: A Dynamic Approach to Data Transfer At the heart of the internet's ability to seamlessly deliver everything from cat videos to critical financial transactions lies the Transmission Control Protocol, or TCP. This protocol acts as the unsung hero, ensuring that the data you send and receive arrives intact and in the...]

To truly appreciate the sliding window's elegance, we must dissect its core components. These elements work in concert, orchestrating the flow of data and providing the reliability we've come to expect from the internet. Let's explore the key players: window size, acknowledgments, sequence numbers, retransmission, and buffering.

Window Size: The Receiver's Capacity

The window size is arguably the most fundamental aspect of the sliding window mechanism. It represents the amount of data (in bytes) that the receiver is currently prepared to accept. Think of it as the receiver's buffer capacity, advertised to the sender.

The receiver broadcasts its window size to the sender in the TCP header of its acknowledgment packets. This is crucial information, giving the sender a clear indication of how much data it can transmit without overwhelming the recipient.

Dynamic Adjustment: Adapting to Changing Conditions

Importantly, the window size is not static. It dynamically adjusts throughout the connection, reflecting the receiver's current processing capabilities.

If the receiver is busy, it can shrink the window size, signaling the sender to slow down. Conversely, if the receiver has ample resources, it can increase the window size, allowing for faster data transfer. This adaptive behavior is key to efficient and reliable communication.

Acknowledgments (ACKs): Confirming Receipt

Acknowledgments, or ACKs, play a vital role in confirming successful data delivery. When the receiver successfully receives a TCP segment, it sends an ACK back to the sender, indicating that the data has arrived safely.

The ACK contains the sequence number of the next expected byte, effectively acknowledging all previous bytes.

Cumulative Acknowledgments: Boosting Efficiency

TCP uses cumulative acknowledgments, meaning a single ACK can acknowledge multiple segments. This significantly improves efficiency by reducing the number of ACK packets required. Instead of acknowledging each segment individually, the receiver can acknowledge a range of segments with a single ACK.

Sequence Numbers: Maintaining Order

Sequence numbers are the backbone of TCP's reliability. Each byte of data transmitted is assigned a unique sequence number. These numbers guarantee that packets arrive at the destination in the intended order, even if they take different routes across the network.

If packets arrive out of order, the receiver uses the sequence numbers to reassemble them correctly before delivering the data to the application layer.

Detecting Lost Packets: Identifying Gaps

Sequence numbers also help detect lost packets. If the sender doesn't receive an ACK for a particular sequence number within a reasonable timeframe, it assumes the packet has been lost and needs to be retransmitted.

Retransmission: Ensuring Delivery

The retransmission mechanism is TCP's safety net. It ensures that data is eventually delivered, even if packets are lost or corrupted in transit. When a sender doesn't receive an ACK for a segment, it retransmits that segment after a timeout period.

Timeout Mechanisms: Balancing Speed and Reliability

The timeout period is dynamically calculated, typically based on the estimated round-trip time (RTT) between the sender and receiver. Setting the timeout too short can lead to unnecessary retransmissions, while setting it too long can delay recovery from packet loss.

Buffering: Holding Data in Transit

Buffering is essential on both the sending and receiving sides. The sender buffers data until it's acknowledged, allowing for retransmission if necessary. The receiver buffers data as it arrives, potentially out of order, until it can be reassembled and delivered to the application.

The Relationship Between Buffering and Window Size

The receiver's buffer size directly impacts the window size it advertises. A larger buffer allows the receiver to advertise a larger window, enabling the sender to transmit more data without waiting for acknowledgments. This relationship between buffering and window size is critical for achieving high throughput.

Flow Control: Preventing Receiver Overwhelm

Building upon the mechanics of the sliding window, a critical function emerges: flow control. This mechanism is the guardian of the receiver, preventing it from being overwhelmed by a torrent of data it cannot process.

Flow control ensures smooth, efficient communication by regulating the rate at which the sender transmits data. The sliding window plays a pivotal role in achieving this balance.

The Receiver's Capacity as the Limiting Factor

The core principle of flow control revolves around the receiver's ability to manage incoming data. Every device has limitations in terms of processing power, memory, and buffer space.

If the sender transmits data faster than the receiver can handle it, packets can be dropped, leading to retransmissions and reduced efficiency. The sliding window mechanism mitigates this issue by enabling the receiver to dynamically communicate its capacity to the sender.

How the Sliding Window Enables Flow Control

The receiver advertises its receive window to the sender, essentially indicating how much free buffer space it has available. This window size dictates the maximum amount of data the sender can transmit without receiving an acknowledgment.

The sender must respect the receiver's advertised window size and avoid exceeding it. This creates a self-regulating system where the receiver maintains control over the flow of data.

If the receiver becomes congested, it can reduce its advertised window size, effectively slowing down the sender. Conversely, if the receiver has ample capacity, it can increase the window size, allowing the sender to transmit more data.

Zero Window Advertisements: Pausing Transmission

In extreme cases, the receiver may become completely overwhelmed and advertise a zero window. This signals the sender to cease transmission immediately.

The sender will then periodically probe the receiver to check if the window size has increased. This probing mechanism prevents a complete deadlock and allows the connection to resume when the receiver is ready.

The Benefits of Effective Flow Control

Flow control provides several significant advantages:

• Prevents Data Loss: By ensuring the receiver is not overwhelmed, it minimizes packet drops due to buffer overflow.

• Improves Efficiency: Reduced retransmissions lead to higher throughput and better overall network performance.

• Ensures Stability: It helps maintain a stable and predictable communication environment, especially under heavy load.

In conclusion, flow control, as implemented by the TCP sliding window, is an essential mechanism for ensuring reliable and efficient data transfer. It empowers the receiver to dictate the pace of communication, preventing overload and maintaining a stable connection.

Congestion Control (Brief Overview): Avoiding Network Overload

While the sliding window primarily manages flow control between a sender and receiver, another crucial mechanism operates to protect the network as a whole: congestion control.

It's tempting to think of these as interchangeable, but their focus differs significantly. Congestion control's purpose is to prevent network overload, a scenario where too many packets compete for limited bandwidth, leading to packet loss and significant performance degradation.

This section offers a brief overview of congestion control, acknowledging its vital role without delving into the intricate details of its algorithms. A full exploration of congestion control algorithms and techniques merits its own dedicated discussion, well beyond the scope of this current exploration.

What is Network Congestion?

Network congestion occurs when the demand for network resources exceeds the available capacity. Picture a highway during rush hour: too many cars attempting to use the same road leads to slowdowns and gridlock.

Similarly, in a network, when the volume of data being transmitted surpasses the network's ability to handle it, congestion arises. This can manifest as:

• Increased packet loss: Routers become overwhelmed and start dropping packets.

• Increased latency: Packets experience longer delays as they queue up at congested routers.

• Reduced throughput: The overall rate of successful data transfer decreases.

The Role of Congestion Control

Congestion control mechanisms aim to prevent or mitigate these issues by regulating the amount of data injected into the network.

Unlike flow control, which focuses on the receiver's capacity, congestion control considers the entire network's ability to handle traffic.

It's a collaborative effort, with senders adjusting their transmission rates based on feedback from the network.

Congestion Control Algorithms

Several congestion control algorithms exist, each employing different strategies for detecting and responding to congestion. Some prominent examples include:

• TCP Reno: One of the earliest and most widely deployed congestion control algorithms. It relies on packet loss as an indicator of congestion.

• TCP NewReno: An improvement over Reno, designed to handle multiple packet losses within a single round-trip time more efficiently.

• TCP CUBIC: A more aggressive algorithm designed for high-bandwidth networks. It uses a cubic function to adjust the congestion window.

• TCP BBR (Bottleneck Bandwidth and Round-trip propagation time): A more recent algorithm that attempts to directly estimate the bottleneck bandwidth and round-trip time of the network path.

These algorithms typically involve:

1. Monitoring network conditions: Observing packet loss, round-trip time, or other metrics.
2. Adjusting the congestion window: Modifying the amount of data the sender can have in transit at any given time.

Why Not a Deep Dive?

The world of congestion control is vast and complex, encompassing numerous algorithms, variations, and ongoing research.

Diving into the intricacies of each algorithm, their performance characteristics, and their interactions with different network environments would require a separate, in-depth treatment.

This brief overview serves to highlight the importance of congestion control as a complementary mechanism to flow control, both essential for reliable and efficient data transfer over the Internet.

For those interested in a more thorough understanding, abundant resources are available, including RFCs, academic papers, and online tutorials. This introduction, however, should sufficiently set the stage for understanding its general function.

[Congestion Control (Brief Overview): Avoiding Network Overload While the sliding window primarily manages flow control between a sender and receiver, another crucial mechanism operates to protect the network as a whole: congestion control. It's tempting to think of these as interchangeable, but their focus differs significantly. Congestion control'...]

Performance Impact: Factors Influencing Sliding Window Efficiency

The TCP sliding window mechanism, while fundamental to reliable data transfer, isn't immune to performance bottlenecks. Its efficiency is intertwined with several factors that can either enhance or degrade its operation. Let's delve into the critical elements influencing the sliding window's performance.

The Pervasive Influence of Round-Trip Time (RTT)

Round-Trip Time (RTT), the time it takes for a packet to travel from the sender to the receiver and back, is a paramount factor affecting TCP performance. A higher RTT directly translates to a longer wait time for acknowledgments. This, in turn, affects how quickly the sending rate can be adapted.

When the RTT is high, the sender remains idle for extended periods while awaiting confirmation of sent data. This underutilizes the available network bandwidth and reduces overall throughput.

Estimating RTT and Setting Retransmission Timeouts

TCP employs sophisticated algorithms, such as Jacobson's algorithm and its derivatives (e.g., TCP Vegas), to estimate RTT dynamically. These algorithms use past RTT samples to predict the current RTT, adapting to fluctuations in network conditions.

The RTT estimate is crucial for setting the retransmission timeout (RTO). The RTO determines how long a sender waits before retransmitting a packet that hasn't been acknowledged. Setting the RTO too low leads to unnecessary retransmissions, increasing network congestion and further reducing performance. Setting it too high causes excessive delays when packets are truly lost.

A well-tuned RTO, based on an accurate RTT estimate, is vital for efficient TCP operation.

Throughput Limitations: The Interplay of Window Size, RTT, and Network Capacity

Throughput, the rate at which data is successfully transferred, is a key performance indicator for any network connection. The TCP sliding window directly impacts throughput. The maximum achievable throughput is often limited by the window size and the RTT, following the formula:

Throughput ≤ Window Size / RTT

This equation highlights the direct relationship between window size, RTT, and achievable throughput. If the window size is small or the RTT is high, the throughput will be limited. Network capacity, of course, acts as a ceiling, beyond which throughput cannot increase regardless of window size or RTT.

In practice, the smallest value among receiver advertised window, congestion window and network capacity becomes the bottleneck.

Optimizing throughput requires careful consideration of these three factors:

• Increasing the window size,
• Reducing RTT, and
• Ensuring sufficient network capacity.

TCP Window Scale Option: Breaking the 64KB Barrier

Historically, the TCP window size was limited to 16 bits, resulting in a maximum window size of 65,535 bytes (64KB). This limitation became a significant bottleneck for high-bandwidth networks. The TCP Window Scale Option (RFC 1323) addresses this limitation.

The Window Scale Option allows the sender and receiver to negotiate a scaling factor that multiplies the advertised window size. This effectively increases the maximum window size to several gigabytes.

By enabling larger window sizes, the Window Scale Option significantly improves throughput on high-bandwidth, high-latency networks.

Without the Window Scale Option, high-bandwidth connections with long RTTs would be severely underutilized.

SACK (Selective Acknowledgment): Enhancing Retransmission Efficiency

Traditional TCP acknowledgments are cumulative, meaning that an ACK confirms receipt of all data up to a specific sequence number. If a packet is lost, the receiver only acknowledges the last contiguous byte received, even if subsequent packets have arrived successfully.

This can lead to multiple retransmissions of packets that have already been received, a phenomenon known as "retransmission ambiguity."

Selective Acknowledgment (SACK), defined in RFC 2018, allows the receiver to acknowledge non-contiguous blocks of data that have been received. This helps the sender precisely identify which packets are missing and need retransmission, avoiding unnecessary retransmissions.

SACK significantly improves TCP performance, especially in environments with high packet loss. By reducing retransmission ambiguity, SACK allows TCP to recover from packet loss more quickly and efficiently, leading to higher overall throughput.

TCP Standards: The Foundation of TCP Protocol

While the sliding window primarily manages flow control between a sender and receiver, another crucial aspect underpins the entire TCP edifice: the standards that define its operation. It's tempting to think of TCP as a monolithic entity, but its behavior is precisely defined and meticulously documented in a series of Request for Comments (RFCs). These RFCs serve as the authoritative source for understanding the protocol's inner workings and ensuring interoperability across different implementations.

Understanding these standards, especially core RFCs, is crucial for anyone working with network protocols, debugging network issues, or designing network applications.

The Importance of RFCs

RFCs are not just dry technical documents; they are the foundation upon which the entire TCP ecosystem is built. They provide a common language and a set of rules that allow different devices and software to communicate effectively. Without these standards, the Internet as we know it would not be possible.

RFCs ensure interoperability. Without a standardized specification, different implementations of TCP would likely be incompatible, leading to communication breakdowns.

They provide a definitive reference. When questions arise about TCP's behavior, the RFCs provide the ultimate source of truth.

They evolve with the technology. As the Internet evolves, so too does TCP. New RFCs are published to address new challenges and improve performance.

Core RFCs: A Closer Look

Several RFCs are particularly important for understanding TCP. Let's examine some of the foundational ones:

RFC 793: The Original TCP Specification

Published in 1981, RFC 793, titled "Transmission Control Protocol," represents the original definition of TCP. It lays out the fundamental concepts, including connection establishment (the three-way handshake), data transfer, reliable delivery using sequence numbers and acknowledgments, and connection termination.

RFC 793 introduced the core concepts still relevant today, describing the TCP header format, state transition diagram, and the procedures for handling various error conditions.

It's important to remember that while subsequent RFCs have updated and expanded upon RFC 793, this document remains the bedrock of the protocol.

RFC 1122: Requirements for Internet Hosts - Communication Layers

RFC 1122, published in 1989, is titled "Requirements for Internet Hosts - Communication Layers." This document clarifies and expands upon the requirements for TCP implementations, addressing ambiguities and providing more specific guidance.

It is an essential companion to RFC 793, detailing aspects like reliable retransmission procedures, addressing issues around minimum retransmission timeout (RTO), and persistent connections.

RFC 1122 aims to promote more robust and interoperable TCP implementations by clarifying requirements for Internet hosts. It is not just about TCP but also touches upon other protocols like IP and ARP, providing a comprehensive overview of communication layers.

RFC 1323: TCP Extensions for High Performance

As network speeds increased, the original TCP specifications became a bottleneck. RFC 1323, published in 1992 and titled "TCP Extensions for High Performance," addresses this issue by introducing the TCP Window Scale Option.

This extension allows TCP to use window sizes larger than the original 65,535-byte limit, which became a constraint on high-bandwidth networks.

Without window scaling, TCP throughput would be severely limited on fast networks with high latency. RFC 1323 also introduced TCP timestamps, which are used for round-trip time (RTT) measurement and Protection Against Wrapped Sequence numbers (PAWS).

Navigating the RFC Landscape

The world of RFCs can be daunting. Here are a few tips for navigating this landscape:

• Start with the core RFCs. Focus on RFC 793, RFC 1122, and RFC 1323 to build a solid foundation.
• Use the RFC index. The RFC Editor website provides a comprehensive index of all RFCs, allowing you to search by keyword or topic.
• Consult online resources. Many websites and online communities offer explanations and tutorials on TCP and RFCs.
• Understand the "obsoletes" and "updates" relationships. Newer RFCs often obsolete or update older ones. Pay attention to these relationships to ensure you're consulting the most current information.

The TCP standards, as defined in the RFCs, are not just theoretical documents; they are the practical blueprints that guide the implementation and operation of the Internet's most important transport protocol. By understanding these standards, you gain a deeper appreciation for the complexities of network communication and the importance of open standards in ensuring a reliable and interoperable Internet.

Practical Analysis: Tools for Observing TCP in Action

[TCP Standards: The Foundation of TCP Protocol While the sliding window primarily manages flow control between a sender and receiver, another crucial aspect underpins the entire TCP edifice: the standards that define its operation. It's tempting to think of TCP as a monolithic entity, but its behavior is precisely defined and meticulously documented... ]

Understanding the theoretical underpinnings of TCP, especially the sliding window mechanism, is essential. However, truly mastering TCP requires practical experience—seeing it in action.

Fortunately, several powerful tools are available to dissect TCP traffic, allowing you to observe its nuances and debug issues effectively. These tools enable you to peek behind the curtain and witness the intricate dance of packets, acknowledgments, and window adjustments that constitute a TCP connection.

Wireshark: Your Window into Network Traffic

When it comes to network analysis, Wireshark reigns supreme. This free and open-source packet analyzer has become the de facto standard for network professionals and enthusiasts alike.

Wireshark's popularity stems from its powerful features, user-friendly interface, and extensive community support. It allows you to capture network traffic in real-time and analyze it with unparalleled granularity.

Capturing and Filtering TCP Traffic with Wireshark

Wireshark can capture traffic from a variety of network interfaces, including Ethernet, Wi-Fi, and loopback interfaces.

Once you've started a capture, Wireshark displays a live stream of packets, each meticulously dissected and presented in a hierarchical format.

To focus on TCP traffic, you can use Wireshark's powerful filtering capabilities. Simply enter "tcp" in the filter bar to display only TCP packets.

You can further refine your filters to target specific IP addresses, port numbers, or even specific TCP flags. For example, tcp.port == 80 will filter for TCP traffic on port 80 (typically HTTP).

Analyzing TCP Segments: A Deep Dive

Once you've filtered for TCP traffic, Wireshark allows you to examine individual TCP segments in detail.

Selecting a TCP segment reveals a wealth of information, including source and destination ports, sequence numbers, acknowledgment numbers, window size, and TCP flags.

This detailed view allows you to trace the flow of data, observe acknowledgments, and identify potential problems such as retransmissions or window updates.

Interpreting TCP Flags: SYN, ACK, FIN, and More

TCP flags are single-bit fields within the TCP header that signal specific events or states in the connection lifecycle.

Understanding these flags is crucial for interpreting TCP behavior. Key flags include:

• SYN (Synchronization): Used to initiate a TCP connection.
• ACK (Acknowledgment): Acknowledges the receipt of data.
• FIN (Finish): Signals the end of a connection.
• RST (Reset): Abruptly terminates a connection.
• PSH (Push): Indicates that the data should be delivered to the application immediately.
• URG (Urgent): Signals the presence of urgent data.

By analyzing the sequence of TCP flags, you can reconstruct the state of a connection and identify potential issues such as connection resets or failed handshakes.

Observing the Sliding Window in Action

Wireshark provides valuable insights into the dynamics of the TCP sliding window.

By examining the window size field in TCP headers, you can observe how the receiver advertises its available buffer space to the sender.

You can also track the sequence and acknowledgment numbers to understand how the sender and receiver are coordinating data transfer.

Analyzing the changes in window size over time can reveal how the receiver is managing flow control and preventing overload. Retransmissions, also easily identified in Wireshark, are clear indicators of packet loss and potential network issues.

Practical Applications of Wireshark in TCP Analysis

Wireshark is an indispensable tool for a wide range of TCP-related tasks, including:

• Troubleshooting network performance issues: Identifying bottlenecks and latency problems.
• Debugging application connectivity problems: Pinpointing issues with TCP handshakes or data transfer.
• Analyzing network security: Detecting malicious traffic patterns or vulnerabilities.
• Learning about TCP internals: Gaining a deeper understanding of how TCP works by observing it in action.

By mastering Wireshark, you gain the ability to diagnose and resolve a wide range of network issues, making it an essential skill for anyone working with TCP-based applications or networks.

So, that's the TCP sliding window in a nutshell! Hopefully, you now have a better grasp of how it works its magic to make sure data gets from point A to point B reliably and efficiently. Remember, the whole purpose of the TCP sliding window is to control the flow of data, preventing overwhelming the receiver and ensuring smooth communication. Happy networking!