Tethering
Tethering is the process of sharing a mobile device's cellular data connection with another device, such as a laptop or tablet, typically through Wi-Fi hotspot, USB, or Bluetooth connections, effectively turning the smartphone into a portable modem.[1][2][3]
This functionality emerged prominently in the mid-2000s alongside the rise of smartphones and 3G networks, enabling greater mobility for internet access but often restricted by carriers seeking to monetize it separately from standard data plans.[4]
Key methods include Wi-Fi tethering, which creates a local hotspot for multiple devices; USB tethering, offering a wired, lower-latency connection ideal for single-device use; and Bluetooth tethering, which conserves battery but supports fewer simultaneous connections and lower speeds.[5][6]
While tethering facilitates on-the-go computing and has supported remote work and travel, it raises data consumption rapidly, potentially incurring overage fees, and drains the host device's battery significantly.[1][7]
Controversies persist as mobile carriers frequently detect and block unauthorized tethering via traffic analysis—distinguishing it from direct device usage through patterns like increased web protocol traffic—and enforce extra charges or plan requirements, prompting regulatory scrutiny over network openness and user rights.[8][9][10]
Definition and Fundamentals
Core Concept and Functionality
Tethering refers to the process by which a mobile device shares its active cellular data connection with one or more other devices, enabling internet access where direct cellular service is unavailable or insufficient on the client devices. This functionality positions the mobile device as an intermediary gateway, akin to a portable modem or router, routing inbound and outbound data packets between the cellular network and connected clients.[2][6] At its core, tethering operates through network sharing mechanisms that leverage the mobile device's existing data subscription, typically provided by a cellular carrier such as LTE or 5G networks. The tethered device performs address translation and traffic management to integrate client devices into the cellular IP address space, ensuring compatibility with standard internet protocols. Common connection methods include Wi-Fi hotspot creation for multiple wireless clients, USB tethering for direct wired links offering higher speeds and lower latency, and Bluetooth pairing for low-bandwidth, short-range sharing.[11][12] Functionally, tethering consumes the host device's data quota and battery resources proportionally to the connected traffic volume, with Wi-Fi hotspots supporting up to 10 or more simultaneous connections depending on hardware capabilities, while USB methods prioritize stability for single-device use. Carrier policies frequently meter or restrict tethering to prevent abuse of unlimited plans intended for personal device use, often enforcing detection via traffic pattern analysis or additional fees for explicit tethering add-ons.[13][14]Primary Methods of Implementation
Tethering primarily operates through three methods: Wi-Fi hotspot, USB tethering, and Bluetooth tethering, each leveraging the mobile device's cellular data connection to provide internet access to secondary devices.[3][2] Wi-Fi hotspot functionality enables the mobile device to create a local wireless access point, allowing multiple devices to connect simultaneously via standard Wi-Fi protocols such as 802.11. This method supports higher bandwidth, typically up to the limits of the device's cellular plan, but consumes significant battery power due to continuous radio transmission.[15][14] USB tethering establishes a wired connection between the mobile device and a host computer using a USB cable, configuring the phone as a network interface or modem on the host system. It offers stable, low-latency performance with speeds often exceeding wireless alternatives and minimal battery drain on the tethered device, as the USB connection can supply power. This approach is limited to a single host device and requires compatible USB drivers or built-in OS support.[16][2] Bluetooth tethering pairs the mobile device with another via Bluetooth PAN (Personal Area Network) profiles, routing data at lower speeds—typically under 3 Mbps—making it suitable for low-bandwidth tasks like email but inefficient for streaming or large downloads. It preserves more battery life than Wi-Fi due to Bluetooth's lower power profile and supports connections from multiple devices in theory, though practically limited by pairing constraints.[17][6]Historical Development
Origins in Early Mobile Computing
Tethering emerged in the late 1990s as mobile phones transitioned from analog voice services to digital networks supporting rudimentary data capabilities, allowing users to connect devices like laptops or personal digital assistants (PDAs) to cellular modems embedded in phones. Initial setups relied on physical connections such as serial cables or infrared ports to enable laptops to dial into cellular networks for internet access, often using software like Nokia PC Suite or Palm HotSync for synchronization and modem emulation. These methods provided slow, circuit-switched data rates typical of 2G GSM networks, around 9.6 kbps, primarily for email retrieval and basic web browsing by mobile professionals in environments lacking fixed-line infrastructure.[4] The commercialization of General Packet Radio Service (GPRS) in 2000-2001 revolutionized early tethering by introducing packet-switched data, offering "always-on" connectivity at theoretical speeds up to 114 kbps without tying up voice channels. This enabled more efficient sharing of cellular data with portable computers, such as Compaq iPaq PDAs or early Windows CE laptops, via USB or Bluetooth profiles like Dial-Up Networking (DUN). Devices like the Ericsson R380 (2000) and Nokia 9210 Communicator supported such configurations through proprietary software, bridging the gap between standalone cellular modems (e.g., PCMCIA cards) and integrated phone-based sharing.[18] By 2003-2005, as EDGE (Enhanced Data rates for GSM Evolution) extended GPRS speeds to 384 kbps, tethering gained traction in enterprise settings with smartphones like the Palm Treo 600 and BlackBerry 7230, which facilitated USB and Bluetooth connections to laptops running Windows XP or Palm OS. Verizon's 2005 promotion of high-speed EV-DO tethering on devices like the LG VX4400 exemplified vendor-supported implementations, though carrier restrictions on data usage often limited adoption. These developments addressed the mobility demands of early mobile computing, where laptops lacked built-in cellular radios, but required rigorous software configuration to route IP traffic through the phone's modem.[4]Expansion with Smartphone Ecosystems
The expansion of tethering accelerated with the proliferation of smartphones in the late 2000s, as devices like the original iPhone in 2007 and early Android phones integrated advanced cellular data capabilities with built-in sharing protocols, transforming mobile internet from a supplementary feature into a core ecosystem component. Prior to widespread smartphone adoption, tethering was limited to basic Bluetooth or USB connections on feature phones and PDAs, often requiring specialized hardware or software hacks, but smartphones enabled seamless Wi-Fi hotspots and reverse tethering, leveraging 3G networks for broader accessibility. This shift coincided with the rollout of high-speed mobile data, allowing users to share connections with laptops and tablets, effectively turning smartphones into portable routers.[4] Palm's Pre and Pixi devices, released in 2009 and 2010, marked early milestones by introducing native Wi-Fi hotspot functionality on smartphones, predating similar features in dominant platforms and highlighting the potential for ecosystem-wide connectivity. Android followed suit with Wi-Fi tethering in its Froyo (2.2) update in May 2010, enabling users to broadcast cellular data as a hotspot without additional hardware. Apple's iOS introduced Personal Hotspot on the Verizon iPhone 4 in February 2011, extending it broadly via iOS 4.3 in March 2011, which integrated USB, Bluetooth, and Wi-Fi sharing optimized for Apple ecosystems like MacBooks. These implementations spurred adoption, as smartphone sales surged—global shipments exceeded 1 billion units annually by 2013—driving tethering into everyday use for remote work and travel.[19][4][20] Carrier resistance initially hampered expansion, with operators like AT&T, Verizon, and T-Mobile imposing software blocks on unauthorized tethering apps in 2011 to preserve revenue from premium data plans and prevent erosion of fixed broadband subscriptions. These restrictions, often enforced through network detection of anomalous traffic patterns or OS-level interventions requested from Google, reflected economic incentives: unlimited smartphone plans subsidized lighter usage, while tethering enabled heavier, multi-device consumption. Regulatory pressure, including FCC scrutiny in 2011 and a 2012 settlement forcing Verizon to unblock tethering without extra fees for certain plans, compelled carriers to formalize support, integrating it into standard offerings by the mid-2010s.[21][22][23] By the early 2010s, tethering's embedding in smartphone ecosystems facilitated the growth of companion devices, such as tablets and wearables, which relied on phone-hosted networks for data offloading, reducing the need for separate cellular subscriptions. The advent of 4G LTE in 2010 further amplified this, with devices like the HTC Evo 4G supporting higher throughput for shared connections, contributing to a 6,000-fold increase in global mobile data traffic over the decade. Despite ongoing carrier caps—often limiting hotspot data to 5-50 GB monthly—tethering became a standard feature, underscoring smartphones' role as central hubs in personal networks.[19][24]Technical Mechanisms
Underlying Protocols and Network Sharing
Tethering relies on standard networking protocols to share a mobile device's cellular or other upstream internet connection with client devices, functioning as a gateway or router. The primary mechanisms involve Network Address Translation (NAT) for multiplexing traffic from multiple clients through the device's single upstream IP address, and Dynamic Host Configuration Protocol (DHCP) for dynamically assigning private IP addresses (typically in the 192.168.x.x or 10.x.x.x ranges) to connected clients within a local subnet.[25][26] These protocols ensure isolation of the local network from the upstream provider while enabling outbound internet access, without employing advanced routing protocols such as RIP, as the setup emulates a simple access point-to-WAN bridge.[27] For Wi-Fi-based tethering, the mobile device configures itself as a wireless access point using IEEE 802.11 standards, broadcasting an SSID for clients to join. Upon connection, the device runs a DHCP server to lease IPv4 (and optionally IPv6) addresses to clients, often defaulting to a /24 subnet like 192.168.43.0/24, configurable on some platforms via advanced settings.[28][29] NAT masquerades client traffic, rewriting source IPs to the device's cellular interface IP for upstream forwarding, while handling return packets via connection tracking.[26][30] This setup supports dual-stack IPv4/IPv6 where available, with eBPF-based offloading possible on modern implementations for efficiency.[25] USB tethering employs USB-over-IP protocols to present the mobile device as an Ethernet adapter to the host computer. The predominant protocol is RNDIS (Remote Network Driver Interface Specification), a Microsoft-developed standard that encapsulates Ethernet frames over USB, allowing the host to treat the connection as a standard network interface without additional drivers on supported OSes.[31] Alternatives include CDC-ECM (Communications Device Class - Ethernet Control Model) or CDC-NCM for higher speeds, which similarly enable IP traffic tunneling via USB 2.0 or higher, with the mobile device providing DHCP or static IP configuration to the host.[32] No NAT is typically required on the host side, as the mobile device routes traffic directly.[33] Bluetooth tethering utilizes the Personal Area Network (PAN) profile under Bluetooth specifications, creating a wireless personal area network (WPAN) for IP sharing. Ethernet packets are encapsulated using BNEP (Bluetooth Network Encapsulation Protocol), enabling Layer 3 transport over Bluetooth links, with the mobile device acting as a network access point (NAP) or group ad-hoc network (GN) role.[34][35] An older alternative is the Dial-Up Networking (DUN) profile for PPP-based access, though PAN/BNEP predominates for Ethernet-like efficiency; DHCP and NAT operate similarly to Wi-Fi tethering to manage client IPs and upstream sharing.[36] These methods prioritize low-bandwidth scenarios due to Bluetooth's inherent speed limits compared to Wi-Fi or USB.[37]Hardware and Software Requirements
Tethering necessitates a source device, typically a smartphone, with an integrated cellular modem supporting data connectivity via technologies such as HSPA, LTE, or 5G, along with an active SIM card and data plan.[3] The hardware must include interfaces for sharing: a Wi-Fi chipset compatible with access point (AP) mode for wireless hotspots, a USB port (e.g., USB 2.0 or USB-C) for wired tethering, or a Bluetooth radio supporting the Personal Area Network (PAN) profile for Bluetooth tethering.[38][39] For optimal performance, especially in high-throughput scenarios, devices benefit from hardware offload capabilities that enable direct IP packet forwarding between the cellular modem and sharing interface, bypassing the main CPU to reduce latency and power consumption.[38] Without such features, software-based implementations like eBPF tethering offload in Android 11 or later can mitigate bottlenecks by optimizing packet processing in kernel space.[25] Client devices require corresponding hardware—Wi-Fi/Bluetooth receivers or USB host ports—and software drivers to recognize the tethered connection, such as USB networking drivers on PCs.[40] Software requirements center on operating system support for network address translation (NAT), Dynamic Host Configuration Protocol (DHCP) server functionality, and firewall rules to manage shared traffic securely.[25] On Android devices, tethering is natively available on most models running Android 2.2 or later, configurable via settings for Wi-Fi, USB, or Bluetooth methods, though carrier restrictions may apply.[3] Similarly, iOS devices support hotspot features from iOS 4.3 onward, but implementation details vary by platform. Advanced setups, like Ethernet tethering via USB adapters, demand additional hardware compatibility and OS-level recognition of the peripheral.[41] Battery life and thermal management are critical considerations, as tethering increases power draw; devices without efficient hardware acceleration may experience rapid depletion during prolonged use.[42]Platform-Specific Support
Android Implementation
Android's tethering functionality is provided through the Tethering module in the Android Open Source Project (AOSP), which enables sharing of the mobile data or Wi-Fi connection with client devices via Wi-Fi, USB, Bluetooth, or Ethernet.[25] The system supports both IPv4 (with NAT and DHCP) and IPv6 (with SLAAC) protocols, with traffic forwarded between upstream (e.g., cellular) and downstream (tethered) interfaces using iptables rules for masquerading and routing.[43][25] USB tethering was introduced in Android 2.2 Froyo, released in May 2010, alongside initial Wi-Fi hotspot support, allowing devices to share connections without third-party apps on compatible hardware.[44] Upon activation, the Android device exposes a virtual network interface to the host using the Remote Network Driver Interface Specification (RNDIS) protocol over USB, enabling the host to receive an IP address via DHCP from the phone's netd daemon, typically in the 192.168.42.0/24 subnet.[33] This method provides stable, low-latency sharing but requires USB debugging disabled and compatible drivers on the host OS, such as Windows or Linux kernels with CDC Ethernet support.[45] Wi-Fi tethering operates by configuring the device's Wi-Fi chipset as a software access point (Soft AP), managed through the WifiManager API for settings like SSID, WPA2/WPA3 security, maximum clients (often 8-10, device-dependent), channel selection via Automatic Channel Selection (ACS), and client allow/block lists.[46] The IpServer component provisions downstream interfaces with dnsmasq for DHCP (defaulting to 192.168.43.0/24), while upstream traffic undergoes NAT via iptables chains like natctrl_tether and filter FORWARD.[25] Bluetooth tethering, also available since early versions, uses the Bluetooth PAN profile to form an ad-hoc network, pairing the devices before enabling reverse tethering mode on the Android side for lower-bandwidth scenarios like legacy device connectivity.[25] The ConnectivityService oversees tethering states, interface pairing, and provisioning checks, including carrier-specific entitlements via the TetheringManager API since Android 8.0.[43] Recent enhancements include eBPF offloading for kernel-bypassed packet processing (Android 11+), reducing CPU overhead for high-throughput scenarios like IPv6 downloads, and split tunneling via VpnService.Builder#excludeRoute (Android 13+), allowing selective routing of tethered traffic.[25] Data usage is tracked by the framework for tethered pairs returned by ConnectivityService.getTetheredIfacePairs(), aiding in billing and policy enforcement, though OEMs and carriers may overlay restrictions like app-based provisioning or hidden plan requirements.[43] Activation occurs via Settings > Network & Internet > Hotspot & tethering, with callbacks like TetheringEventCallback providing IP and state updates for apps.[47][46]iOS Implementation
Apple's iOS implements tethering via the Personal Hotspot feature, available on iPhone and iPad models with cellular capability, allowing users to share their active cellular data connection with compatible devices.[48] This functionality requires an eligible carrier plan that explicitly supports hotspot usage, as carriers control activation through SIM provisioning or account settings.[49] Without such support, the Personal Hotspot option remains disabled in iOS settings, reflecting carrier-imposed restrictions rather than inherent software limitations.[50] To activate Personal Hotspot, users access the Settings app, navigate to the Personal Hotspot submenu under Cellular (or Mobile Data), and toggle the feature on, which generates a Wi-Fi network name and password by default.[48] iOS supports three primary tethering methods: Wi-Fi for wireless access point sharing, USB for direct wired connection to computers, and Bluetooth for paired device networking.[51] Wi-Fi tethering configures the iOS device as a soft access point using the integrated Wi-Fi chipset, supporting up to five simultaneous connections with WPA3-Personal encryption for security, which provides forward secrecy and protection against brute-force attacks on the passphrase.[52] USB tethering activates automatically upon connecting a compatible cable to a host device like a Mac or Windows PC, bypassing wireless overhead for lower latency and reduced battery drain, while presenting as a network interface without additional driver installation on macOS.[53] Bluetooth tethering involves pairing the devices first via Bluetooth settings, followed by selecting the iOS device as the internet source on the client, though it offers lower throughput suitable only for low-bandwidth tasks due to protocol inefficiencies.[17] For seamless integration within Apple's ecosystem, iOS incorporates Instant Hotspot, leveraging Bluetooth Low Energy (BLE) and iCloud authentication to enable passwordless connections from nearby signed-in Apple devices, such as Macs or other iOS/iPadOS hardware, without broadcasting the hotspot publicly.[54] This uses cryptographic keys derived from the user's iCloud account for mutual authentication, ensuring only authorized devices join while maintaining end-to-end encryption for data transit.[54] However, cross-platform connectivity to non-Apple devices requires manual entry of the Wi-Fi credentials, and all tethered traffic routes through the iOS device's cellular modem, applying network address translation (NAT) and DHCP services internally to manage client IP assignments from a private subnet.[51] Carrier detection of tethered usage often relies on traffic analysis, such as decremented Time-to-Live (TTL) values in IP packets indicating routing hops beyond the mobile device, enabling enforcement of plan-specific data caps or throttling for hotspot activity separate from direct cellular use.[55] iOS does not expose low-level configuration options like APN settings for hotspot in user interfaces, deferring such customizations to carrier profiles updated via over-the-air mechanisms, which can limit flexibility compared to more open platforms.[56] As of iOS 18 in 2025, Personal Hotspot continues to prioritize stability and security over advanced customization, with automatic disconnection after inactivity to conserve battery and data, though users can monitor connected devices and usage via the Settings interface.[48]Cross-Platform and Desktop Integration
Wi-Fi hotspot tethering provides the most straightforward cross-platform integration for desktops, as major operating systems including Windows, macOS, and Linux support connecting to ad-hoc or infrastructure Wi-Fi networks created by mobile devices. Users enable the hotspot feature on the phone, enter the SSID and password in the desktop's Wi-Fi settings, and establish a connection without additional drivers or software.[57] This method operates over standard 802.11 protocols secured by WPA2 or WPA3, ensuring compatibility across ecosystems but potentially introducing latency compared to wired options.[58] USB tethering offers higher speeds and stability for single-device connections but requires protocol-specific support varying by mobile platform and desktop OS. Android devices typically employ the RNDIS protocol for USB tethering, which is natively recognized by Windows through automatic driver installation upon connection.[59] Linux kernels include the rndis_host module for seamless RNDIS handling, while macOS lacks built-in support and necessitates third-party drivers such as HoRNDIS to enable the connection.[44][60] iOS USB tethering, conversely, integrates natively with macOS via Apple's proprietary IP-over-USB implementation, appearing as an Ethernet interface once Personal Hotspot is activated.[51] On Windows, it demands installation of Apple Mobile Device USB drivers, often bundled with iTunes, to recognize the iPhone as a network adapter.[61] Linux support for iOS involves packages like libimobiledevice, usbmuxd, and the ipheth kernel driver, though configuration may require manual steps such as listing devices with idevice_id.[62] Bluetooth tethering utilizes the Personal Area Network (PAN) profile for integration, supported across Android, iOS, and desktop OS but limited to lower bandwidths around 2-3 Mbps, making it suitable only for light usage.[63] Pairing occurs via standard Bluetooth settings, followed by enabling the PAN connection, with no additional hardware required beyond compatible adapters on desktops. Cross-platform challenges arise primarily in USB scenarios due to proprietary protocols and driver dependencies, favoring Wi-Fi for universal accessibility despite its shared-medium inefficiencies.[64]Carrier and Regulatory Landscape
Economic and Operational Rationales for Limitations
Mobile carriers impose tethering limitations primarily to safeguard revenue models predicated on differentiated data services, as unrestricted sharing enables a single plan to replicate fixed broadband functionality for multiple devices, eroding sales of premium add-ons or dedicated hotspot plans. [65] For instance, operators without extensive wireline infrastructure, such as T-Mobile in 2015, incur higher wholesale Internet access fees from competitors like Verizon and AT&T when tethering drives extreme usage volumes—potentially 300 GB to 1 TB monthly—escalating costs beyond those calibrated for smartphone-only consumption. [65] This pricing strategy reflects carriers' recognition that tethering data commands a premium, with plans often allocating separate, throttled quotas (e.g., T-Mobile's 7 GB cap on its $80/month unlimited tier at the time) to monetize high-demand scenarios while discouraging substitution for home Internet. [65] [66] Operationally, tethering amplifies network strain because connected devices like laptops sustain bandwidth-intensive tasks—streaming higher-resolution video or downloading large files—that exceed smartphone norms by up to threefold, overwhelming capacity planned for lighter mobile patterns. [65] Licensed spectrum scarcity, governed by physical limits like Shannon's theorem on channel capacity, constrains overall throughput; unchecked tethering by heavy users risks congestion, degrading speeds for broader subscriber bases reliant on efficient LTE or 5G allocation. [65] Carriers thus enforce distinctions via access point names (APNs) or traffic shaping, throttling hotspot data after thresholds (e.g., AT&T's 22 GB limit in 2015) to preserve quality of service and avert infrastructure upgrades disproportionate to average demand. [65] These measures align with capacity management practices, blocking or upselling tethering to curb abuse and sustain viable economics amid rising data traffic. [66]Policies in Key Jurisdictions
In the United States, following the Federal Communications Commission's 2017 repeal of its Open Internet Order, mobile carriers are not federally required to permit unrestricted tethering or to treat tethered data identically to direct device usage, granting providers latitude to impose data caps, throttling, or surcharges on hotspot functionality as long as terms are disclosed in service agreements. This shift reversed earlier 2010 guidelines that scrutinized carrier blocks on tethering apps, such as those enforcing usage detection to prevent circumvention of plan limits.[67] Carriers like Verizon and AT&T commonly include tethering allowances in premium plans (e.g., up to 30-60 GB before throttling as of 2025), but unlimited plans often restrict high-speed hotspot data to avoid network congestion. Within the European Union, the "Roam Like at Home" regulation (Regulation (EU) 2017/920) integrates tethering into domestic data allowances without additional fees for intra-EU/EEA usage, provided it adheres to fair use thresholds designed to curb abuse like permanent cross-border tethering for non-residents. Operators may monitor and limit excessive hotspot sharing if it exceeds typical personal consumption (e.g., 50-100 GB monthly averages per BEREC guidelines), but outright blocks are prohibited unless transparently justified for network management.[68] This policy, extended through 2032, has boosted intra-EU data roaming volumes by over 100% since 2017 by treating hotspots equivalently to on-device data. In the United Kingdom, post-Brexit oversight by Ofcom mandates clear disclosure of tethering terms in contracts but does not enforce unrestricted access, allowing providers to apply fair usage policies similar to pre-2020 EU norms, with typical high-speed hotspot limits of 20-80 GB on unlimited tariffs before speed reductions to 2-5 Mbps.[69] No statutory ban exists, though roaming tethering outside the UK incurs standard international rates unless covered by provider passes.[13] China imposes no explicit regulatory ban on tethering, but all mobile data sharing occurs under the Ministry of Industry and Information Technology's real-name SIM registration and Great Firewall oversight, subjecting tethered traffic to the same content filtering and surveillance as direct usage, with potential service disruptions for VPN circumvention attempts.[70] Operators like China Mobile enforce plan-specific data caps, often throttling after 3-10 GB daily.[71] In India, the Telecom Regulatory Authority of India (TRAI) regulates tethering indirectly through tariff transparency rules under the 2023 Telecommunications Act, requiring operators to specify hotspot allowances without mandating equivalence to on-device data; providers commonly permit it but deploy usage detection to enforce add-on fees or throttling beyond 1-2 GB daily on base plans.[72] No federal prohibition applies, aligning with TRAI's emphasis on infrastructure sharing over end-user restrictions.[73]| Jurisdiction | Key Regulatory Body | Tethering Stance | Notable Limits/Requirements |
|---|---|---|---|
| United States | FCC | Permitted; carriers may restrict post-2017 net neutrality repeal | Disclosure required; e.g., 30-60 GB high-speed on premium plans |
| European Union | European Commission/BEREC | Included in data allowances under roaming rules; fair use applies | No surcharges intra-EU; monitor for abuse (e.g., >50 GB/month) |
| United Kingdom | Ofcom | Permitted with disclosed terms; no equivalence mandate | Fair use caps (20-80 GB); roaming surcharges outside UK[13] |
| China | MIIT | Permitted but censored; real-name SIM enforced | Plan caps (3-10 GB/day); Firewall applies to all traffic[71] |
| India | TRAI | Permitted per operator terms; transparency required | Detection-based throttling (1-2 GB/day base); no ban[72] |