Re: Feasible to implement a router on a system on a chip?

Keith M wrote:
David Brown wrote:

I certainly can't imagine what you'd want with 64 MB flash - even if you run a non-specialised kernel such as Linux on your router, the kernel, all the networking, routing and filtering code, and the basic configuration tools will fit in about 2 MB. Add another 2 MB for a fancy web interface if you want.

Cisco's executable images are up to 20mb a pop, and that firmware is stored in the flash. I forget whether 20mb is compressed or not -- it might be. Cisco is the big dog with lotsa features, so they might be an extreme case.

I tried like heck this morning to find the memory timeline/roadmap on Cisco's site, but no can do. However the Cisco 3845 data***

http://www.cisco.com/en/US/prod/collateral/routers/ps5855/product_data_sheet0900aecd8016a8e8.html


and see under memory

• Default-64 MB Compact Flash; 256 MB DDR SDRAM

I honestly don't know what the breakdown of why that much is required --- but can tell you from practical experience that 64/256mb is considered standard for low-midrange (Note I'm specifically excluding SOHO routers) full-featured routers. The Cisco 3845 maxes out around T3 speeds. The larger routers have larger requirements --- but note that memory doesn't scale with bandwidth........ you don't necessarily need more memory to support higher throughput.

However, I can tell you that having support for many different types of modules, many different WAN protocols, VPN support, firewall support, VOIP support, etc etc etc Executable image size and memory requirements can skyrocket. Memory requirements are going to hinge exactly on what features you intend on supporting.

Keith

I had a little look at the link you gave - the Cisco box shown there does not look remotely like the sort of device I imagine the OP is thinking of. As far as I can tell, he is thinking of a routing packets as fast as possible between networks, not handling the packets on the system itself (except as needed for routing protocols). The Cisco box is for connecting together LANs, telephones, WLANs, WANs and VPNs, and thus needs vastly more software support. 20 MB compressed firmware still sounds a bit bloated (I have routers supporting LANs, WLANs, VPNs, WANs, NAT, firewalls, and many other TLAs, running from about 2.5 MB compressed firmware), but nearly as much in view of all the other stuff it supports.
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