TY - GEN
T1 - Space-efficient TCAM-based classification using gray coding
AU - Bremler-Barr, Anat
AU - Hendler, Danny
PY - 2007/9/4
Y1 - 2007/9/4
N2 - Ternary content-addressable memories (TCAMs) are increasingly used for high-speed packet classification. TCAMs compare packet headers against all rules in a classification database in parallel and thus provide high throughput unparalleled by software-based solutions. TCAMs are not well-suited, however, for representing rules that contain range fields. Such rules have to be represented by multiple TCAM entries. The resulting range expansion can dramatically reduce TCAM utilization. The majority of real-life database ranges are short. We present a novel algorithm called short range gray encoding (SRGE) for the efficient representation of short range rules. SRGE encodes range borders as binary reflected gray codes and then represents the resulting range by a minimal set of ternary strings. SRGE is database independent and does not use TCAM extra bits. For the small number of ranges whose expansion is not significantly reduced by SRGE, we use dependent encoding that exploits the extra bits available on today's TCAMs. Our comparative analysis establishes that this hybrid scheme utilizes TCAM more efficiently than previously published solutions. The SRGE algorithm has worst-case expansion ratio of 2 W - 4, where W is the range-field length . We prove that any TCAM encoding scheme has worst-case expansion ratio W or more.
AB - Ternary content-addressable memories (TCAMs) are increasingly used for high-speed packet classification. TCAMs compare packet headers against all rules in a classification database in parallel and thus provide high throughput unparalleled by software-based solutions. TCAMs are not well-suited, however, for representing rules that contain range fields. Such rules have to be represented by multiple TCAM entries. The resulting range expansion can dramatically reduce TCAM utilization. The majority of real-life database ranges are short. We present a novel algorithm called short range gray encoding (SRGE) for the efficient representation of short range rules. SRGE encodes range borders as binary reflected gray codes and then represents the resulting range by a minimal set of ternary strings. SRGE is database independent and does not use TCAM extra bits. For the small number of ranges whose expansion is not significantly reduced by SRGE, we use dependent encoding that exploits the extra bits available on today's TCAMs. Our comparative analysis establishes that this hybrid scheme utilizes TCAM more efficiently than previously published solutions. The SRGE algorithm has worst-case expansion ratio of 2 W - 4, where W is the range-field length . We prove that any TCAM encoding scheme has worst-case expansion ratio W or more.
UR - http://www.scopus.com/inward/record.url?scp=34548357302&partnerID=8YFLogxK
U2 - 10.1109/INFCOM.2007.164
DO - 10.1109/INFCOM.2007.164
M3 - Conference contribution
AN - SCOPUS:34548357302
SN - 1424410479
SN - 9781424410477
T3 - Proceedings - IEEE INFOCOM
SP - 1388
EP - 1396
BT - Proceedings - IEEE INFOCOM 2007
T2 - IEEE INFOCOM 2007: 26th IEEE International Conference on Computer Communications
Y2 - 6 May 2007 through 12 May 2007
ER -