VPN Efficiency Optimization for Remote Work: Improving Speed and Stability

Why VPN Efficiency Optimization Matters for Remote Work

As telework has become established, business communications over VPN have surged, and complaints such as slow VPN speeds, frequent disconnections, and frozen video conferences have emerged across many organizations. Companies near Shinagawa have found that while VPN quality was not initially a concern at the start of telework adoption, increasing user counts and the shift to cloud services have led to growing VPN bandwidth congestion. VPN efficiency optimization is not merely about speed improvement — it is an initiative that simultaneously enhances employee productivity, reduces IT department incident response workload, and improves communication quality while maintaining security levels. This article provides practical VPN efficiency optimization techniques explained from a network engineer's perspective. We deliver immediately actionable measures for IT administrators who feel their VPN is too slow and executives considering telework environment improvements.

Optimal Split Tunneling Configuration While Maintaining Security

Split tunneling is the most immediately effective measure for VPN efficiency optimization. In full tunnel configurations that route all traffic through the VPN, cloud service communications for Microsoft 365 (Teams, OneDrive, SharePoint), Zoom, and Slack also transit through the VPN gateway, and it is not uncommon for 50 to 70 percent of bandwidth to be consumed by cloud-bound traffic. Switching to split tunneling routes only internal resource traffic through the VPN while cloud services are accessed directly from the endpoint, dramatically reducing VPN bandwidth consumption. In FortiGate, enable Split Tunnel and specify only internal subnets in the Routing Address. In Cisco AnyConnect, set the ASA's Split-Tunnel-Policy to tunnelspecified and define internal networks via ACL. From a security perspective, since traffic outside the VPN is unprotected in split tunnel environments, deploying EDR solutions like CrowdStrike Falcon or Microsoft Defender for Endpoint on all devices and protecting internet traffic with cloud proxies such as Zscaler Internet Access or Cisco Umbrella for defense-in-depth is recommended.

MTU Optimization to Prevent VPN Communication Fragmentation

Improper MTU (Maximum Transmission Unit) settings are a primary cause of VPN communication performance degradation. Standard Ethernet MTU is 1500 bytes, but VPN tunnels add encapsulation headers that reduce the effective MTU. IPsec VPN (ESP plus new IP header) adds approximately 58 bytes of overhead, while SSL VPN (TLS headers) adds roughly 40 to 80 bytes, causing packets that exceed the MTU to undergo fragmentation and reassembly processing. The general recommendation for VPN environments is to set the client-side MTU to 1400 bytes, reducing to 1392 bytes in PPPoE environments. On Windows, this can be configured from the command prompt with the command netsh interface ipv4 set subinterface with the VPN connection name, mtu of 1400, and store set to persistent. On FortiGate, optimize both the DTLS tunnel and tunnel IP pools via CLI under config vpn ssl settings, along with setting ssl-max-proto-ver to tls1-3 for protocol version optimization. Ensuring Path MTU Discovery works correctly by allowing ICMP Type 3 Code 4 (Fragmentation Needed) through firewalls along the path is also critical.

DNS Cache and Local DNS Configuration Optimization

DNS name resolution easily becomes a bottleneck in VPN environments, and proper DNS configuration contributes significantly to VPN efficiency. In full tunnel configurations, all DNS queries are sent through the VPN to the internal DNS server, meaning DNS response times directly affect web page load speeds. Implementing split DNS directs name resolution for internal domains such as *.company.local to the internal DNS server while using ISP DNS or public DNS services like Cloudflare at 1.1.1.1 or Google at 8.8.8.8 for all other internet domains. FortiGate enables per-domain DNS routing through the split-dns setting under config vpn ssl web portal. On the client side, leverage Windows DNS client caching and add A records for frequently accessed servers to the hosts file for faster name resolution. Windows allows cache status verification with ipconfig /displaydns and suffix search optimization through Set-DnsClientGlobalSetting with the appropriate SuffixSearchList. For large-scale environments, consider deploying DNS caching servers such as Unbound or dnsdist.

QoS Settings and Traffic Prioritization for Stable Video Conferencing

QoS (Quality of Service) settings are a critical measure for ensuring video conferencing and IP telephony quality in bandwidth-constrained VPN environments. Configuring traffic shaping on the VPN gateway to assign high priority to real-time communications (voice and video) while setting bulk data transfers like file transfers and backups to low priority enables efficient allocation of limited bandwidth. FortiGate allows creating per-application shaping rules under config firewall shaping-policy, setting guaranteed bandwidth for Microsoft Teams and Zoom traffic. Cisco ASA uses policy-map and class-map to define traffic classes, with the priority command assigning highest-priority bandwidth to voice traffic. Leveraging DSCP (Differentiated Services Code Point) marking to tag packets within the VPN tunnel with priority values enables priority handling by network devices along the path. One IT company in Shinagawa dramatically reduced Teams video conferencing freezes from over 20 per week to only 2 to 3 per month after implementing QoS settings.

VPN Protocol Tuning: WireGuard vs OpenVPN Speed Comparison

VPN protocol selection and configuration significantly impact communication speeds. OpenVPN is the most widely used open-source VPN, but since it runs in user space, it tends to deliver lower throughput compared to WireGuard, which operates in kernel space. Actual benchmarks on identical environments (1 Gbps connection, same server) show WireGuard achieving 800 to 950 Mbps versus 200 to 400 Mbps for OpenVPN (UDP, AES-256-GCM), with WireGuard recording 2 to 4 times higher throughput. WireGuard's codebase is approximately 4,000 lines, making security auditing significantly easier compared to IPsec at over 400,000 lines and OpenVPN at over 100,000 lines. On the other hand, OpenVPN can communicate over TCP port 443, offering superior traversal in strict firewall environments, with years of operational track record and robust enterprise support. When considering integration with FortiGate or Cisco products, optimizing existing SSL VPN/IPsec VPN infrastructure through FortiGate DTLS mode activation or IPsec VPN IKEv2 optimization is more practical than adding WireGuard as a separate layer. For new deployments considering open-source VPN, WireGuard is a compelling choice from speed and simplicity perspectives.

Bandwidth Management and SD-WAN Integration for VPN Optimization

SD-WAN (Software-Defined Wide Area Network) is a technology that logically integrates multiple WAN connections including fiber, LTE, and cable to automatically select the optimal path based on the application. Combining VPN environments with SD-WAN enables advanced controls such as automatic failover to LTE when the primary connection fails, direct internet breakout for Microsoft 365 traffic, and automatic routing of real-time communications to connections with the lowest jitter and latency. FortiGate's SD-WAN feature uses Performance SLA to continuously monitor WAN connection quality, automatically switching paths based on packet loss rate, latency, and jitter thresholds. Cisco Meraki MX and VeloCloud (VMware SD-WAN) also have proven track records as SD-WAN solutions for SMBs. Regarding deployment costs, FortiGate's SD-WAN feature is included in the UTM license at no additional charge, while dedicated SD-WAN solutions incur monthly operating costs of approximately 30,000 to 100,000 yen. Multiple companies in the Shinagawa and Ota areas have dramatically improved VPN communication stability by combining dual WAN configurations with fiber and mobile connections through SD-WAN.

VPN Connection Monitoring Tools and Troubleshooting Methods

Continuous VPN efficiency optimization requires connection state visibility and early problem detection. FortiGate's FortiAnalyzer provides unified dashboard management of VPN connection logs, traffic volumes, and authentication events, enabling bandwidth usage trend analysis and peak-hour identification. For open-source monitoring, PRTG Network Monitor (free for up to 100 sensors) or Zabbix can perform SNMP monitoring of VPN gateways, providing real-time monitoring of CPU utilization, concurrent connections, and interface traffic. When troubleshooting VPN speed issues, first measure non-VPN speeds using speedtest.net as a baseline, then measure VPN speeds with iperf3 to identify the difference. If packet loss is the cause, use mtr (My TraceRoute) to investigate the path to the VPN gateway, and for fragmentation issues, use ping with the do-not-fragment flag and a 1400-byte payload to the VPN gateway IP to confirm MTU problems. One company in Shinagawa reduced their average VPN incident detection time from 30 minutes to 3 minutes after implementing Zabbix monitoring, significantly reducing the impact duration of outages.

Client-Side Optimization: Device Settings and Network Environment Improvements

VPN efficiency optimization is important not only on the server side but also on the client (device) side. First, in Windows network adapter settings, set the VPN adapter's receive window auto-tuning level to normal to optimize TCP receive buffer sizes. If unnecessary background communications such as Windows Update, OneDrive sync, and cloud backups are consuming VPN bandwidth, adjust synchronization schedules during business hours or configure split tunneling to route these communications outside the VPN. For unstable home Wi-Fi, consider switching to wired LAN, moving to the 5 GHz Wi-Fi band, or upgrading to a Wi-Fi 6 router at approximately 5,000 to 15,000 yen. VPN client versions also matter — updating to the latest versions such as FortiClient 7.x or Cisco Secure Client 5.x applies performance improvements including DTLS support and TLS 1.3 compatibility. In the Shinagawa, Meguro, and Setagaya areas, apartment-type fiber connections frequently experience bandwidth degradation during evening hours, leading more companies to consider providing mobile routers for teleworking employees.

Measuring VPN Optimization Results and Establishing a PDCA Cycle

To maximize the effectiveness of VPN efficiency measures, quantitative measurement and PDCA cycle establishment are essential. KPIs to regularly measure include VPN download and upload speeds in Mbps, average VPN connection latency in milliseconds, monthly VPN incident count, video conferencing quality scores measured through tools like Microsoft Teams Call Quality Dashboard, and help desk ticket counts for VPN-related issues. Compiling these metrics into monthly reports and comparing pre- and post-implementation results enables objective evaluation of which measures delivered what level of improvement. For example, demonstrating that split tunneling reduced VPN bandwidth usage by 60 percent, MTU optimization improved large file transfer speeds by 40 percent, and QoS settings improved video conferencing quality scores from 3.2 to 4.5 provides concrete numbers for executive reporting and securing approval for additional investment. Within the PDCA cycle, quarterly analysis of VPN environment usage patterns and continuous identification and remediation of new bottlenecks ensures sustained quality improvement in telework environments.

Telework Environment Improvement Case Studies from Companies Near Shinagawa

Here are real-world VPN efficiency optimization case studies from companies in the Shinagawa area. An IT company in Shinagawa with 40 employees migrated from full tunnel to split tunnel and enabled FortiGate DTLS mode, resulting in a threefold average improvement in VPN communication speeds and significantly better Teams video quality. A manufacturing company in Ota with 25 employees implemented VPN gateway MTU optimization and QoS settings, reducing CAD data transfer time from 15 minutes to 5 minutes and improving design department productivity. A consulting firm in Meguro with 15 employees deployed WireGuard with SD-WAN via FortiGate's built-in feature for dual WAN configuration, reducing VPN disconnections from over 10 per month to less than 1. The common thread across these cases is that problems were quantified first, followed by implementation of appropriately combined measures. Similar improvement results can be expected for companies in Minato, Shibuya, and Setagaya as well.

VPN Efficiency and Telework Improvement Consulting — Contact Oflight Inc.

Oflight Inc., based in Shinagawa, provides comprehensive VPN efficiency optimization and telework environment improvement support for companies across Minato, Shibuya, Setagaya, Meguro, Ota, and the greater Tokyo area. From VPN speed measurement and analysis to split tunnel configuration, MTU optimization, QoS settings, and SD-WAN deployment, we propose optimal improvement measures tailored to each client's environment. We optimize existing FortiGate, Cisco, and Palo Alto environments and also offer cost-efficient solutions leveraging open-source VPN options like WireGuard and SoftEther. If your organization is struggling with telework communication quality or considering a VPN environment review, please contact us for a complimentary initial assessment. We will diagnose your current VPN environment and provide improvement projections along with specific recommended measures.