PDF 原檔：報告_OCP2026_Arista_Broadcom_SUE-T_20261015_original.pdf
講者公開簡報（OCP 官方 Recorded Content 頁提供下載）。文字以 PyMuPDF 逐頁抽取，
### p<n>為頁碼；圖表內容見原檔。
圖片清單（已驗證 2026-10-19）
| 檔名 | 頁 | 分類 | 親眼所見內容 |
|---|---|---|---|
報告_OCP2026_Arista_Broadcom_SUE-T_20261015_p3.png |
p3 | 真資料圖 | SUE-T 範圍表：單跳（可延伸多跳）、最多 4k XPU、Load/Store/Atomics、共享記憶體、E2E 延遲 <2µs RTT、2+ 流量類別；右側為 XPU 晶片周邊多組 SUE-T＋ETH 示意 |
報告_OCP2026_Arista_Broadcom_SUE-T_20261015_p4.png |
p4 | 真資料圖 | SUE-T 方塊圖：XPU NOC→位址轉譯 Map→每目的地 TX buffer→Schedule/Pack→Reliability（UET RODL）→Network Encap（ESUN）→Ethernet MAC/PHY（LLR），接收路徑對稱，PFC/CBFC 回饋 |
報告_OCP2026_Arista_Broadcom_SUE-T_20261015_p5.png |
p5 | 真資料圖 | SUE-T 分層結構：XPU interconnect→Map/Schedule→Reliability→Network header→Ethernet（例如 ESUN）MAC／FEC／PMD |
報告_OCP2026_Arista_Broadcom_SUE-T_20261015_p7.png |
p7 | 真資料圖 | UET RODL 可靠性標頭欄位與效率：payload 256B 線路效率 85%、1KB 96%；5nm 估算面積 LLR only <2mm²、Retx（6µs）<3mm² |
原始內容
p1
Tom Emmons Software Engineer, Arista Networks Inc. Karen Schramm Vice President, Broadcom Inc. SUE-T – An Ethernet transport for Scale-Up Networking AI CLUSTERS
p2
• Scale up transport on XPUs have used proprietary solutions • Open solutions did not meet the efficiency and latency requirements • Broad industry investment in advancing transports and ETH link optimizations • OCP ESUN, Ultra Ethernet Transport (UET), UEC LLR and CBFC, etc. • Value of using standardized protocols is increasing • Scale-up and scale-out lines are converging, storage is directly attached • In-network compute (INC) available in switches Why SUE-T? specifies a network interface with guidance on trade-offs optimized for wire efficiency and low latency area efficient solution based on open standards SUE-T
p3
Feature Primary Target Notes Network scale Single hop Extensible to multi-hop Number of XPUs Up to 4k Ethernet addressing, no practical limit Transaction types Load/Store/Atomics Optimized for small transactions Memory architecture Shared memory Direct address translation E2E latency < 2us RTT No hard limit Affects buffer size Traffic Classes 2+ Separate request and response SUE-T Scope Area Optimized
p4
• Accept XPU transactions • Buffer per destination • Schedule packets to the network • UET RODL transport • Reliable, ordered delivery • OCP ESUN • Compact L2/L3 header • Symmetric receive path SUE-T Overview UET ESUN SUE-T
p5
• XPU to SUE-T connection • AXI or simple signaled interface • Packing, buffering and scheduling • Transactions are pipelined with minimal buffering • Buffering enables packing multiple transactions in a single packet for increased wire efficiency • Transport and network headers are optimized • UET Semantic header for opcode and control • UET RODL transport header for reliable delivery • ESUN header for L2/L3 forwarding SUE-T Structure Ethernet packets XPU transaction XPU interconnect PMD / PHY FEC / PMA / PMD Reconciliation Ethernet MAC Network header Reliability Map / Schedule interface Ethernet (e.g., ESUN) SUE-T
p6
UET Semantics • SES header carries opcode and control • Compact 12B header • use ehl option to carry XPU specific fields • single transactions up to 16K-1 bytes • Enables: • opcode write, read, atomic • jobid user isolation • mm packing multiple transactions in one packet (more messages) • ac address compression, reduce header to 8 bytes SUE-T Semantic Header
p7
• Reliable ordered protocol • Avoid bitmap tracking • Implementation efficient • Keep endpoint simple • Choose retransmission or LLR UET Reliability - RODL Wire efficiency (per payload size) 256B – 85% 1KB – 96% Die size (5nm estimate) LLR only < 2mm2 Retx (6us) < 3mm2 • Uses: • cumulative ack ACK received packets, minimize need for ACK packets • clear ACK read/atomic responses, optional • flags static or dynamic connections SUE-T Reliability Header
p8
Acknowledgements and Error Handling • UET Mode – enhanced error handling • ACK indicates destination successfully processed the transaction • Unsuccessful transactions return error – this error state is saved until cleared • ‘Operation ACK mode’ • Delivery Mode • ACK only indicates the transaction was delivered successfully to destination • Separate message used to carry response to transaction • ‘Delivery ACK mode’
p9
• ESUN Header • Mac header addressing • IP-like Forwarding Semantics • Lossless Link Technologies • CBFC, LLR • UDP encapsulation supported • UET destination port 4793 OCP ESUN SUE-T over ESUN
p10
• Join the SUE-T working group • https://ocp-all.groups.io/g/ocp-net-sue-t • Join UEC to contribute to ULN and other adjacent technologies • https://ultraethernet.org/ Come work with us