Weak spending by service providers, and poor performance in the mobile core market, were among the factors which contributed to a flat third quarter for Cisco, and a negative outlook for the full year, though its WiFi business remained strong. Performance by individual businesses goes up and down of course – switching was up 2% in the fiscal third quarter, compared to the year-ago period, whereas it was a low point of the second quarter results. But more general trends are at work too, notably the industry’s transition from hardware to software and virtualization, making mincemeat of the business models and margins to which Cisco has been accustomed. These underlying patterns are putting huge pressure on the firm, which has…