Odd Mesh Header Date: 2008-03-17 Authors: March 2008 Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 Odd Mesh Header Date: 2008-03-17 Authors: Javier Cardona et al. John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 Abstract Odd mesh header affects alignment of upper layer headers. Why not make it even? Javier Cardona et al. John Doe, Some Company

An 802.11 frame in the standard... Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 An 802.11 frame in the standard... Javier Cardona et al. John Doe, Some Company

A typical 802.11 frame in memory... Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 A typical 802.11 frame in memory... Possible sizes (bytes): 2-byte aligned: 26, 30 4-byte aligned: 24, 28, 32, 36 Javier Cardona et al. John Doe, Some Company

Odd Mesh Header... Mesh Header Sizes (bytes): 5, 11, 17 or 23 Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 Odd Mesh Header... Mesh Header Sizes (bytes): 5, 11, 17 or 23 Javier Cardona et al. John Doe, Some Company

Why is alignment important? Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 Why is alignment important? For efficiency, upper layer expect packets correctly aligned. 4-byte is common. DMA access, cache lines, MMU, all benefit when data is aligned to certain byte-boundaries. Some wireless cards do already add padding bytes to the 802.11 header to make it 4-byte aligned. And some can only add 2*n sized padding. Javier Cardona et al. John Doe, Some Company

Month Year doc.: IEEE 802.11-yy/xxxxr0 March 2008 Straw Poll Would you be interested in a proposal to make the Mesh Header length... 1) 4*n 2) 2*n 3) Leave as is mesh flags: 1 mesh seq:4 mesh TTL: 1 mesh seq: 4 address: 6 [ae > 0] address: 6 [ae > 1] address: 6 [ae > 2] reserved: 2 [ae == 0 or ae == 2] Javier Cardona et al. John Doe, Some Company