Packet Classification using Tuple Space Search

Author: V. Srinivasan, S. Suri, G. VarghesetPublisher: ACM SIGCOMM 1999Presenter: Sih-An PanDate: 2013/11/27

Tuple Space Search Our scheme is motivated by the observation that

while filter databases contain many different prefixes or ranges, the number of distinct prefix lengths tends to be small.

Suppose we have a filter database FD with N filters, and these filters result in m distinct tuples.

Since m tends to be much smaller than N in practice, even a linear search through the tuple set is likely to greatly outperform the linear search through the filter database.

Tuple Space Search We can define a tuple for each combination of

field length, and call the resulting set tuple space. By concatenating these bits in order we can

create a hash key, which can then be used to map filters of that tuple into a hash table.

Rule Specification Tuple

R1 (00*,001*) (2,3)

R2 (0000,0*) (4,1)

R3 (*,1111) (0,4)

R4 (0000,0111) (4,4)

R5 (111*,11*) (3,2)

R6 (*,*) (0,0)

R7 (011*,01*) (3,2)

Tuple Hash Table Entries

(0,0) {R6}

(0,4) {R3}

(2,3) {R1}

(3,2) {R5,R7}

(4,1) {R2}

(4,4) {R4}

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0

0 1

0 1 2 3

Tuple Space Search The port numbers, however, are often specified

using ranges, and the number of bits specified is not clear.

To get around this, we define the length of a port range to be its nesting level.

Rule Specification Tuple

R1 (00*,001*,[0,15]) (2,3,0)

R2 (0000,0*,[6,7]) (4,1,2)

R3 (*,1111,[8,8]) (0,4,2)

R4 (0000,0111,[0,7]) (4,4,1)

R5 (111*,11*,[10,13]) (3,2,2)

R6 (*,*,[8,16]) (0,0,1)

R7 (011*,01*,[4,4]) (3,2,2)

RangeIDLevel

0

1

2

Tuple Pruning Algorithm

[0,0][0,4]

[2,3]

[3,2] [3,2]

[4,1][4,4]

[0,0]

[2,3]

[3,2] [3,2]

[4,1]

[4,4] [0,4]

Packet = {0000, 01*}

Source Trie Destination Trie

Source Tuple List = {[0,0], [0,4], [2,3], [4,1], [4,4]}Destination Tuple List = {[0,0], [4,1], [3,2]}Intersected Tuple List = {[0,0], [4,1]}

Tuple Pruning Algorithm

Markers and Precomputation Consider a tuple = [, , . . . , ]. = [, , . . . , ] belongs to set Short () if and only if

,for all = ,and = [, , . . . , ] belongs to set Long () if and only

if ,for all = ,and A tuple , where , that is neither in Short()nor in

Long() belongs to the incomparable set IC().

Markers and Precomputation

Source IP Length

Des

tinati

on IP

Len

gth T

Short(T)

Long(T)

IC(T)

The main idea is that a probe into a tuple can be used to eliminate a subset of the tuple space.

Markers

Des

tinatio

n IP

Len

gth

Source IP Length

R5(111*,11*) M5(111*,1*) M5(111*,*)

R1(00*,001*) M1(00*,00*) M1(00*,0*) M1(00*,*)

Precomputation

Des

tinat

ion

IP L

engt

h

Source IP Length

R5(111*,11*) M5(111*,1*) M5(111*,*,R6)

R6(*,*)

Rectangle Search The search terminates when the we reach therightmost column or the first row. Since there are Wrows and W columns, the number of probes needed is at most 2W - 1

Rectangle Search

Des

tinat

ion

IP L

engt

h

Source IP Length

R2(0000,0*) M4(0000,0*)

R4(0000,0111) M4(0000,01*) M4(0000,011*) M2(0000,*,R6) M4(0000,*,R6)

R5(111*,11*) M5(111*,1*) M5(111*,*,R6)

M1(00*,0*) M1(00*,*,R6)

M3(*,1*) M3(*,11*) R6(*,*) M3(*,*)

M3(*,111*) R3(*,1111)

M1(00*,00*) R1(00*,001*)

P(0000,0000)

Storage Efficiency

 Throughput (Worst Case)

Throughput (Avg. Case)