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Recursively Partitioned Static IP Router Table. Authors : Wencheng Lu, Sartaj Sahni Publisher : ISCC 2007 Present : Kuang-Ying Ho 何冠穎 Date : 2007/11/06(Tue.). Department of Computer Science and Information Engineering National Cheng Kung University, Taiwan R.O.C. Introduction. - PowerPoint PPT Presentation
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Recursively Partitioned Static IP Router Table
Department of Computer Science and Information Engineering National Cheng Kung University, Taiwan R.O.C.
Authors : Wencheng Lu, Sartaj Sahni
Publisher : ISCC 2007
Present : Kuang-Ying Ho 何冠穎
Date : 2007/11/06(Tue.)
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Introduction
A method–recursive partitioning–to partition a static IP router table so that when each partition is represented using a base structure such as a multibit trie (MST) or a hybrid shape shifting trie (HSST).
Reduce both
Total memory required for router table.
Number of memory access.
Compare with popular front-end table methed.
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*Shape Shifting Trie
K: node size in STT
SBM Shape Bitmap 2K bit
IBM Internal Bitmap
(valid bit)
K bits
EBM External Bitmap (exit point)
K+1 bits
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Recursive Partitioning
R s : 3 R
First-level partitions of Tpartition L(R)the auxiliary partition
s : stride, 1 ≤ s ≤ T.height+1
s : 2
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Q(N) : bit stringIndex of ST(N)
Data structure
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Hash table - Entry types
R s : 2
For first levels : stride
ht : address of first hash table entry
h : perfect hash function
d : destination IP
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Lookup
q u
Incorporating Leaf Pushing
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R
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Lookup after leaf pushing
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Dynamic Programming Recurrence
B(N, l, r) be the minimum memory required to represent levels 0 through l of the subtree of T rooted at N by a base structure such as MBT or HSST take no more than r memory accesses.
H(N, l) be the memory required for a stride l hash table for the paths from node N of T to nodes in Dl(N)
C(N, l, r) be the minimum memory required by a recursively partitioned representation of the subtrie defined by levels 0 through l of ST(N).
r = 4, 5 0 < l ≤ N.height N
N
Q
N.height
l
Recurrences for B may be obtained from Sahni and Kim [12] for fixed- and variable-stride MBTs and Lu and Sahni [6] for HSSTs.
Optimization
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A. when auxiliary partitions L(R) are restricted to be resented by base structures, the memory requirement is reduced.
B. either a hash table or a simple array with 2l entries can be use when the partition stride is l.
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Implementation
For benchmarking purposes we assumed that the router table will reside on a QDRII SRAM (dual burst), which supports the retrieval of 72 bits of data with a single memory access. We considered two hash-table designs–36 bit and 72 bit.
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Implementation for IPv4
In the 36-bit design for IPv4, we allocated 36 bits to each hash entry with: 8 bits for Q(N), 2 bits for the stride of the next-level partition (5-8), 8 bits for the mask, 17 bits for the pointer.
In the 72-bit design for IPv4, we allocated 72 bits for each hash-table entry with17 bits for Q(N), 5 bits for the stride of the next-level partition (1-17),17 bits for the mask,19 bits for the pointer
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Implementation for IPv6
In the 36-bit design for IPv6, we allocated 36 bits to each hash entry with: 7 bits for Q(N), 2 bits for the stride of the next-level partition (4-7), 7 bits for the mask, 19 bits for the pointer.
In the 72-bit design for IPv6, we allocated 72 bits for each hash-table entry with17 bits for Q(N), 5 bits for the stride of the next-level partition (1-17),17 bits for the mask,19 bits for the pointer
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Performance for IPv4
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Performance for IPv6
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Contributions