--- title: Lab Meeting Minutes 2022/4/15 tags: lab_meeting --- > Outline > [TOC] --- # PERAL Lab Meeting - 時間:111 年 4 月 15 日 10:30 (預計) - 地點:TC 321 - 出席者:吳坤熹老師、謝萬霖、周以恆、吳騰然、劉怡君、田蕙瑜、洪胤勛、丘世宇、莊才賢 - 會議主題: [Characterization and Measurement of TCP Traversal through NATs and Firewalls](https://docs.google.com/presentation/d/1dqGloH0kTMQqrCtJUcaUULMINNjOFl4z/edit?fbclid=IwAR3VKEGk8Z-vSpecO05ogyVATNt-yddcJZuAZoaCWYftcJntv_yJQZvZgCo#slide=id.g1248b262dbf_6_86) - 主講者: 田蕙瑜 - 主記: 吳騰然 ## 會議內容 ### Abstract - STUN - Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs) - A lightweight protocol - Allows applications to discover the presence and types of NATs and firewalls between them and the public Internet - Peer to Peer Architecture vs Client Server Archiecture - Client server mode 是以 server 為中心 - Peer to Peer 是去中心化的部分 ![](https://i.imgur.com/n6r9z5u.png) ### Background - NAT can not work in Peer-to-Peer protocol - e.g. Multimedia communication, file sharing - Middlebox Communications [MIDCOM] protocol - allows an application entity to control a NAT - like a Session Initation Protocol [SIP] proxy ### NAT VARIATIONS - NAT VARIATIONS total 4 type : - Full cone NAT (只要 ip address 是固定的,對外的 port 和 ip 都是相同的),cone (圓錐) ![](https://i.imgur.com/mwbSBG6.png) - Address Restricted cone NAT (只要 IP address 不同,就不會進行 NAT 轉換) - 從 NAT 內部送出去的封包其 DESTINATION 會被記錄下來,只有該 DESTINATION 從外部送過來的封包才會被接收。 ![](https://i.imgur.com/Scnd5Km.png) - Port Restricted cone NAT ( 只要 port 不同傳送給 client Data,就不會被進行 NAT 轉換) - 相較於 Address Restricted cone 多了限制條件 Port number。 ![](https://i.imgur.com/FAhoAZb.png) - Synmetric NAT (會有一個 Mapping Table,出去的的 ip address 經過 NAT 轉換,從 client 端傳回來會有對應的 table 表,如果不是 mapping 到 table 內的資料,就不會傳送出去) ![](https://i.imgur.com/BTvakJO.png) ### STUN ARCHITECTURE - STUN is a simple client-server protocol - Request - Binding Request - Shared Secrete Request - TCP ![](https://i.imgur.com/epkvGom.png) - Client send the STUN Reqyest to STUN Server - STUN Server Response ![](https://i.imgur.com/POgiLo6.png) ### STUN MESSAGE - Message Header packet (20 bytes) ![](https://i.imgur.com/wH9YNhv.png) - Message Attributes ### 建議&問題 1. NAT 有甚麼問題 ? 為甚麼需要去解決 [name=solomon] 2. 不要在中途臨時新增新的名詞,會讓人不了解意思 [name=solomon] 3. 所以,STUN server 和 STUN client 之間是交換了甚麼資訊得以穿越 NAT? 在 4 種 NAT 又有什麼不同的方法? [name=Edgar] Ans: 4. NAT1 NAT2 ? [name=branko] Ans: STUN 機制的精神 : 直接透過 NAT 轉換可以直接跟 client 溝通[name=] 5. Address Restricted cone 和 port Restricted cone 可以幫上甚麼忙? [name=chofinn] Ans: 6. P.11 如果有兩台 STUN Server ,如果同時去問是否會式的到相同的結果? [name=Jerry] Ans: 7. P.12 Binding Request 和 Shared Secret Request 是拿來做甚麼用的? [name=Jerry] Ans: over TLS TCP ## 待追蹤事項 1. [name=] Ans : [name=] ## 臨時動議 1. 下禮拜 4/22 Meeting 講者 : Angela,延續今天下去主題[name=solomon] 2. 是否可以發 PPT 的時間可否假日再發佈 Ans: 決議還是七天前發佈 PPT --- 散會結束時間: 12:25
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