From e6e9aaed7fb908276c814dd4eccaebda7915628b Mon Sep 17 00:00:00 2001 From: Teodora Date: Tue, 29 Apr 2025 11:53:55 +0200 Subject: [PATCH] Clarification on the packet length needed to configure VFs As per CUS spec, the MTU can be 1500 or 9000 B, where MTU = IQ data format. Packet length = ethernet header + RTE_PKTMBUF_HEADROOM + MTU However, xran assumes different definitions of the MTU: (1) in xran_init_mbuf_pool(): MTU = ethernet header + IQ data format; (2) in xran_get_num_prb_elm(), xran_init_PrbMap_from_cfg(), xran_init_PrbMap_from_cfg_for_rx(), xran_init_PrbMap_by_symbol_from_cfg(): MTU = complitely wrong (as the IQ data format is not well included). Additionally, xran assumes that the max MTU 9600 B, instead of 9000 B as per spec. Nevertheless, I left 9600 B in all config files and docs due to wrong calculation of (2) for the total number of PRBs per fragment. --- doc/ORAN_FHI7.2_Tutorial.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/doc/ORAN_FHI7.2_Tutorial.md b/doc/ORAN_FHI7.2_Tutorial.md index b486bdb6bf..7aff02f9df 100644 --- a/doc/ORAN_FHI7.2_Tutorial.md +++ b/doc/ORAN_FHI7.2_Tutorial.md @@ -745,7 +745,7 @@ In the following, we will use these short hands: - `IF_NAME`: Physical network interface through which you can access the RU - `VLAN`: the VLAN tag as recommended by the RU vendor -- `MTU`: the MTU as specified by the RU vendor, and supported by the NIC +- `MTU`: this MTU must be higher than supported by the RU vendor due to additional ethernet header of 14 B and DPDK packet header `RTE_PKTMBUF_HEADROOM` of 128 B - `DU_U_PLANE_MAC_ADD`: DU U plane MAC address - `U_PLANE_PCI_BUS_ADD`: PCI bus address of the VF for U plane - `DU_C_PLANE_MAC_ADD`: DU C plane MAC address