Towards TCAM-based Scalable Virtual Routers 2019/10/28 Towards TCAM-based Scalable Virtual Routers Author: Layong Luo, Gaogang Xie, Steve Uhlig, Laurent Mathy, Kavé Salamatian, and Yingke Xie Publisher: ACM CoNEXT 2012 Presenter: Yi-Hao Lai Date: 2015/9/23 Department of Computer Science and Information Engineering National Cheng Kung University, Taiwan R.O.C. CSIE CIAL Lab 1

Introdution Network virtualization allows multiple virtual networks to coexist on an underlying shared substrate, in isolation from each other. When multiple virtual router instances are supported on the same physical equipment, we will use the term virtual router platform. National Cheng Kung University CSIE Computer & Internet Architecture Lab

Virtual router platform Multiple virtual router instances coexist and each has its own FIB (Forwarding Information Base). FIB completion: merges the prefixes from all the FIBs into one TCAM. FIB splitting: mixes the advantages of merged and non-shared data structures by splitting the prefixes into two prefix sets. National Cheng Kung University CSIE Computer & Internet Architecture Lab

non-shared Virtual router ID (VID) National Cheng Kung University CSIE Computer & Internet Architecture Lab

merged If two entries from different FIBs share the same prefix, they can be merged into a single entry in the TCAM-based lookup engines. NH array National Cheng Kung University CSIE Computer & Internet Architecture Lab

merged Union Prefix Set (UPS) National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB completion merged trie A B 2019/10/28 FIB completion merged trie Masking A B National Cheng Kung University CSIE Computer & Internet Architecture Lab CSIE CIAL Lab

FIB completion incoming packet prefix: 011, VID: 1 Result: B1 2019/10/28 FIB completion Original NH Completed NH incoming packet prefix: 011, VID: 1 Result: B1 National Cheng Kung University CSIE Computer & Internet Architecture Lab CSIE CIAL Lab

FIB completion insert National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB completion delete National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB completion masking prefix correction: When an update occurs in a node of the trie, some completed NHs in the sub-trie rooted at that node will have to be updated to reflect correct matching. National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting If only disjoint prefixes are merged in the TCAM, the prefix masking issue does not exist any longer, as at most one prefix in a disjoint prefix set can match a given IP address. About 90% of prefixes in the tries built from real FIBs are leaf prefixes. National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting The disjoint leaf prefixes in the merged trie are stored in one TCAM based on the basic merged data structure. The remaining prefixes in the merged trie are stored in another TCAM using the non-shared approach. National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting update National Cheng Kung University CSIE Computer & Internet Architecture Lab

FIB splitting update National Cheng Kung University CSIE Computer & Internet Architecture Lab

TCAM size For IPv4 FIBs, the largest prefix length is 32 bits. As we can only get a maximum of 14 IPv4 FIBs for the evaluation, a 4-bit VID is enough to identify them. For IPv6 FIBs, the longest prefix is 128 bits. Given a 4-bit VID, the longest virtual prefix is 132 bits. National Cheng Kung University CSIE Computer & Internet Architecture Lab

TCAM size For 14 full IPv4 FIBs, the proposed approaches can achieve a TCAM memory reduction of 92% and 82% National Cheng Kung University CSIE Computer & Internet Architecture Lab

Total Cost of the System National Cheng Kung University CSIE Computer & Internet Architecture Lab

Lookup and Update Performance 2019/10/28 Lookup and Update Performance The worst-case update overhead in FIB completion is 2,206 write accesses per update National Cheng Kung University CSIE Computer & Internet Architecture Lab CSIE CIAL Lab

CCDF of update overhead National Cheng Kung University CSIE Computer & Internet Architecture Lab