Extensive engineering effort to extend TSG's built-in 'APP Sketch DB' fingerprint database with signatures for major domestic Chinese apps (Douyin, Kuaishou, Mango TV, JD, Tencent Cloud, etc.), primarily via SSL SNI matching, with iterative per-feature test/fail/patch cycles against specific in-app actions (e.g. certain Douyin menu items stayed unblocked after the main signature succeeded).

A recurring weekly '[Xinjiang Unicom/Xinjiang Mobile] Traffic Analysis Report' (新疆联通/移动流量分析报告), produced by a 'Carrier Front-End Analysis Team' (运营商前端分析团队), spans Feb-Jul 2023 in this batch. It reports each carrier's total/access bandwidth (Xinjiang Unicom: 1.88 Tbps total, 880 Gbps access; Xinjiang Mobile: 4.4 Tbps total, 1 Tbps access) and per-app server-IP/location/traffic breakdowns for 31 named foreign platforms including Telegram, WhatsApp, Twitter, Facebook, Discord, Snapchat, Gmail and YouTube, alongside domestic-app sections — direct evidence of an ongoing, carrier-integrated domestic monitoring program for China's Xinjiang region.

TSG's app-traffic classification relies on an updatable "App Sketch DB" component (uploaded as a versioned file to each deployment). A version bump at the Xinjiang Unicom province-exit + IDC site increased identified application-traffic share from 23% to 68% of total traffic within days, with ByteDance-attributed traffic alone rising from ~100TB/day to ~500TB/day identified, illustrating both the scale of traffic under classification and that classification itself is a frequently-updated, centrally-distributed database rather than a static build-time artifact.

Side-by-side internal performance comparison across Xinjiang (China Mobile carrier deployment, hostname cmcc-xj-server1-sapp-244), Fujian (domestic), and Ethiopia (E21) explicitly references the same 'app_sketch_maat' diagnostic log format at all three sites, confirming the identical AppSketch app-fingerprinting stack is used for domestic Xinjiang surveillance and for the exported Ethiopia deployment.

Root-caused an Ethiopia SNI-block-failure incident to the detection mechanism itself: APP_SKETCH's FQDN-scanning module -- which exists specifically to identify Psiphon3 and Freegate via top-N SNI matching -- was CPU-expensive enough to saturate cores, triggering sapp's fail-open DDoS bypass and letting some target connections through uninspected. A signature-structure fix roughly doubled throughput (33K/s to 73K/s new connections) and disabling the fail-open bypass restored reliable blocking.

TSG's DPI signature engine is organized around named internal components confirmed by config paths and error logs: SAPP (installed at /home/mesasoft/sapp_run or /opt/tsg/sapp), MAAT (config at .../tsgconf/maat.conf, tied to a Redis-backed APP_SIG_SESSION_ATTRIBUTE_STRING table), and App-SketchDB (a versioned, centrally-maintained app-identification signature database pulled periodically by field deployments). One deployment's provincial gateway alone had 1,667 TCP/UDP first-packet payload signature entries active (396 at the IDC site), confirming payload-prefix matching as a live, large-scale detection method, including custom byte-prefix entries for DingTalk and WeChat.

An internal methodology memo for the '新疆省口项目' (Xinjiang provincial-gateway project) and '联通IDC项目' (Unicom IDC project) states both rely on 现有的系统（TSG与CN） (the existing TSG and CN [CyberNarrator] systems) to Block/Monitor/identify mainstream apps, and describes a largely manual signature-engineering workflow -- download the target app, capture traffic with 科莱(Colasoft Capsa)/Wireshark, extract fingerprint fields (http.host, http.user_agent, quic.sni, ssl.handshake.extensions_server_name) by hand, and register a per-app signature -- extending CyberNarrator's documented role beyond Psiphon-IP-harvesting/Pakistan subscriber correlation into general domestic app-blocking alongside TSG.