nanog mailing list archives
Re: 400G forwarding - how does it work?
From: James Bensley <jwbensley+nanog () gmail com>
Date: Wed, 27 Jul 2022 21:30:07 +0200
On Wed, 27 Jul 2022 at 15:11, Masataka Ohta <mohta () necom830 hpcl titech ac jp> wrote:
James Bensley wrote:The BCM16K documentation suggests that it uses TCAM for exact matching (e.g.,for ACLs) in something called the "Database Array" (with 2M 40b entries?), and SRAM for LPM (e.g., IP lookups) in something called the "User Data Array" (with 16M 32b entries?).Which documentation? According to: https://docs.broadcom.com/docs/16000-DS1-PUB figure 1 and related explanations: Database records 40b: 2048k/1024k. Table width configurable as 80/160/320/480/640 bits. User Data Array for associated data, width configurable as 32/64/128/256 bits. means that header extracted by 88690 is analyzed by 16K finally resulting in 40b (a lot shorter than IPv6 addresses, still may be enough for IPv6 backbone to identify sites) information by "database" lookup, which is, obviously by CAM because 40b is painful for SRAM, converted to "32/64/128/256 bits data".
Hi Masataka, Yes I had read that data sheet. If you have 2M 40b entries in CAM, you could also have 1M 80 entries (or a mixture); the 40b CAM blocks can be chained together to store IPv4/IPv6/MPLS/whatever entries. Cheers, James.
Current thread:
- Re: 400G forwarding - how does it work?, (continued)
- Re: 400G forwarding - how does it work? Saku Ytti (Jul 25)
- Re: 400G forwarding - how does it work? Lawrence Wobker (Jul 25)
- Re: 400G forwarding - how does it work? James Bensley (Jul 25)
- Re: 400G forwarding - how does it work? Lincoln Dale (Jul 25)
- Re: 400G forwarding - how does it work? Jeff Tantsura (Jul 26)
- Re: 400G forwarding - how does it work? Saku Ytti (Jul 26)
- Re: 400G forwarding - how does it work? Jeff Tantsura (Jul 27)
- Re: 400G forwarding - how does it work? James Bensley (Jul 25)
- RE: 400G forwarding - how does it work? ljwobker (Jul 27)
- Re: 400G forwarding - how does it work? Dave Taht (Jul 27)
- Re: 400G forwarding - how does it work? James Bensley (Jul 27)