The first layer of the classifier houses three tables. Effectively, the classifier performs one lookup on a packet-type table, two lookups on a host-group table, and two lookups on a layer 4 table. These results are combined in a main-rule table. SwitchCore points out that the user programs all tables. After the classifier block finishes processing, it outputs a 7-bit result. This allows for 128 traffic classes, which are used for bandwidth distribution and functions like prioritization, filtering packets, and so forth.
Once the packet is classified, the prioritizer can use any of the following parameters to put the packet into one of the eight output queues: 802.1p, type-of-service (ToS) field, traffic class, IP multicast group, layer 2/3 destination address, and VLAN source address. A precedent can be defined between these parameters.
A user may want to give an IP multicast a very high priority for something such as a videoconference setup. If a particular packet wasn't in this group, the prioritizer would look for the next precedence set, for example, the traffic class. Based on the packet's traffic class, the prioritizer also can change its ToS bits. This may be used in a function like DiffServ. To provide QoS, this function changes the ToS bits in the packet.
The CXE architecture also guarantees bandwidth. A user can, for example, guarantee a certain service-level agreement through a particular part of the network. Since the chip can pick out the types of traffic, it's able to distribute the bandwidth based on the traffic class from the classifier.
The CXE architecture uses an algorithm, developed in-house, that's based on fair queuing. It is shown as weighted fair-hashed bandwidth distribution (WFHBD) in Figure 1.
By using that distribution technique, a user can program the equivalent of a weighted round-robin method on the output. Using this method, for example, 10 high-priority packets may be sent to the output, maybe only eight from the next priority queue, and then just one from the lowest-priority queue. Still, that low-priority queue at least gets a turn. This is in sharp contrast to strict priority, where a high-priority packet always is sent first, and a low-priority packet may never be sent. The key here is the fair way in which the chip defines the flow groups within the traffic class.
Moving on to software support, it's the company's belief that software plays an important role for the CXE family. SwitchCore is concerned about time-to-market issues and feels this will be one of the advantages of an off-the-shelf device. Available low-level software drivers basically perform device-level operations, such as register accesses.
The software is modular and, according to the company, simple to operate. The drivers were actually developed for a Motorola PowerPC, but the hooks for the processor are separate files. Users can work with a different processor if they want.
The company plans to supply the software for PowerPCs and the pSOS real-time operating system. But it also thinks that it's relatively easy to perform, for example, a port to MIPS or VxWorks. The basic idea is that because the software is very modular, users can actually pick out the pieces they want. SwitchCore also supplies the source code for the low-level software drivers, so users can get in at that level if they want.
SwitchCore anticipates that the CXE-16 will primarily be used in enterprise applications. The chip could reside on one of the blades inside an enterprise switch. Otherwise, it could function as the backplane interconnect, joining a large number of these blades together.
It also might operate, for example, in a server farm. In that case, some kind of low-profile "pizza box" style enclosure would connect it a number of servers with Gigabit Ethernet cards. According to the company, this would probably be the first application of CXE-16s, or all-gigabit switches, going directly to servers.
PRICE AND AVAILABILITY
The CXE-16 and CXE-1000 are sampling this quarter, with production starting in the fourth quarter of this year. Both chips come in an 836-pin EBGA package. The CXE-16 is priced at $950 each and the CXE-1000 at $450 each in quantities of 1000. The CXE-5000 CAM is sampling in the third quarter of this year, with production slated for the fourth quarter. Pricing is $100 each in quantities of 1000.
SwitchCore Corp., 675 N. First St., PH3, San Jose, CA 95112; (408) 995-3850; fax (408) 995-3858; e-mail: info@switchcore.com; www.switchcore.com.