The exponential growth of the Internet over the last few
decades provides testament to the extreme success of the internet protocol (IP),
the primary protocol responsible for delivering data packets between hosts
across the heavily trafficked internet. Notwithstanding this success, IP address
space is rapidly running out. Consequently, the more complex 128-bit IPv6 will
soon replace the nearly exhausted 32-bit range of the existing IPv4.
IP routers are the devices responsible for physically
employing the IP to forward packets toward their final destination. In order for
an IP router to perform this function, the router must conduct an address
search, then buffer, schedule, and transmit packets to the next hop address
through the appropriate port. Meanwhile, to perform the address search function,
an IP router implements an associate matching process to identify the longest
matching address prefix in its router forwarding table. Because associative
processes are complex, the address search constitutes a key power and speed
bottleneck in the IP.
Researchers at Arizona State University have developed a
novel circuit that addresses the power and speed bottleneck in the IP by
improving the router search function. Specifically, the invention replaces the
conventional ternary content-addressable memory (CAM) that performs the address
search function with a more sophisticated CAM that discretely determines the
longest prefix match to the stored address and outputs the match as a two-part
thermometer code. As a result, one entry replaces an average of 22 TCAM entries;
consequently, these novel CAMs are an order of magnitude smaller than equivalent
TCAMs and dissipate over 90% less dynamic power. Furthermore, because the design
automatically produces an encoded prefix match length limited by the prefix
mask, there is no need to sort the order of the entries. Meanwhile, work to
refine the design and apply it to IPv6 is ongoing.
Potential Applications
- Electronics
- Networks & Communication
Benefits and Advantages
- Improves Address Search Speed for IP Routing ? replaces
an average of 22 conventional TCAM entries with only one; simulations operate
above 1 GHz
- Reduces the Physical Size of the IP CAM Circuit ?
proposed IP CAMs are an order of magnitude smaller in area than conventional
CAMs
- Reduces Dynamic Power Dissipation ? dissipates over 90%
less dynamic power in comparison to conventional CAMs; circuit design density
is an order of magnitude better than convention designs