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Multicast Forwarding Plane in Future NWs: Source Routing Has a Competitive Edge Takeru Inoue Yohei Katayama Hiroshi Sato Takahiro Yamazaki Noriyuki Takahashi.

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Presentation on theme: "Multicast Forwarding Plane in Future NWs: Source Routing Has a Competitive Edge Takeru Inoue Yohei Katayama Hiroshi Sato Takahiro Yamazaki Noriyuki Takahashi."— Presentation transcript:

1 Multicast Forwarding Plane in Future NWs: Source Routing Has a Competitive Edge Takeru Inoue Yohei Katayama Hiroshi Sato Takahiro Yamazaki Noriyuki Takahashi (NTT Labs., Japan) GLOBECOM FutureNet III 1Takeru Network Innovation Labs.

2 Gap between design and usage of Internet Takeru Network Innovation Labs.2  Internet (TCP/IP)  Originally designed for 1:1 conversation model (60’s-70’s)  telnet, ftp, …  NOW: Mainly used for 1:N distribution model  Audio-video streaming, pub/sub services, file sharing, data-center, …  Efficient distribution model  Data is replicated at nodes and delivered to a group  Source and overall network overhead is decreased  Future NWs will support efficient distribution  In accordance with the usage replication

3 Trend in multicast research Takeru Network Innovation Labs.3  History in multicast research  Twenty-year history  Main focus was group size, not group numbers  Recent trends  Supporting many groups (> 1T )  Increase in contents themselves and long-lived services 1. Dr. multicast [Vigfusson08] and MAD [Cho09]  Extend IP multicast for many groups  Handle only large groups and reduce forwarding state 2. FRM and LIPSIN [Ratnasamy06, Jokela09]  Based on source routing  Have no state limit, but suffer from small headers  No clear direction on multicast research for future networks

4 Our contribution and outline Takeru Network Innovation Labs.4  Our contribution  Most promising research direction in multicast  Focused on forwarding plane, because it directly affects quality and is designed before control plane  Outline  Taxonomy of multicast forwarding plane 1. Table-driven forwarding 2. Packet-driven forwarding (source routing)  Scalability improvement techniques: virtual ports, Bloom filters, and hierarchy  Assessment of multicast forwarding plane  Scalability on group number and group size  Forwarding performance  Control architecture  State management

5 External definition of multicast forwarding Takeru Network Innovation Labs.5  Nodes independently determine their output ports  S = F(n, g)  S : set of output ports  F(n,g) : function to determine S  n : node ID  g : group ID  Forwarding state maintained by overall network Packet of Group 1 p1 p2p3 To Ports 2 and 3 Group \ Node n1n2 … g1n1:p2 n1:p3n2:p1 g2 φ n2:p1 n2:p3 :

6 Taxonomy Takeru Network Innovation Labs.6  Table-driven forwarding  Nodes maintain columns (forwarding tables) and search them by group ID in packet  Max group # is limited by table size  e.g. IP multicast  Packet-driven forwarding  Source puts row on packet header  Nodes finds ports  No limit on group #, but group size is limited by header  Kind of source routing (nodes are stateless) Group \ Node n1n2 … g1n1:p2 n1:p3n2:p1 g2 φ n2:p1 n2:p3 : Table-driven forwarding Packet-driven forwarding g1g1 g1: p2 p3 : g1: p2 p3 : n1:p2 n1:p3 … Forwarding state p1 p2p3 p1 p2p3 Packet

7 Review of scalability improvement techniques: Virtual ports Takeru Network Innovation Labs.7  Virtual ports [Tian98, Jokela09]  Set of physical ports  Fork (ports on single node, e.g. vp1 in Fig)  Tunnel (ports on different nodes, e.g. vp2 in Fig)  Reduce forwarding state (tables or headers)  Nodes maintain mapping  Much smaller than forwarding table vp1 … vp1 vp2 vp1: p2 p3 : vp1: p2 p3 : Mapping of virtual ports p1 p2p3 Packet-driven forwarding

8 Review of scalability improvement techniques: Bloom filters Takeru Network Innovation Labs.8  Bloom filters  Probabilistic data structure for set  Has great space efficiency at risk of false positive  e.g. 10 bits per element with 1 % error  Can be checked in constant time h i (x) h i (y) Initial h i (z) ? False positive Add x Add y Check z

9 Review of scalability improvement techniques: Bloom filters Takeru Network Innovation Labs.9  Bloom filters  Probabilistic data structure for set  Has great space efficiency at risk of false positive  e.g. 10 bits per element with 1 % error  Can be checked in constant time  Table-driven forwarding  Bloom filter is assigned to each port and has groups of ports [Gronvall02]  Packet-driven forwarding  Headers are replaced by Bloom filters [Ratnasamy06] p1: … p2: g1 … p3: g1 … p1: … p2: g1 … p3: g1 … p1 p2p3 Bloom filters g1g1 n1:p2 n1:p3 … p1 p2p3 Bloom filter in packet Table-driven forwarding Packet-driven forwarding

10 Review of scalability improvement techniques: Hierarchy Takeru Network Innovation Labs.10  Table-driven forwarding  No improvement  Inter-domain nodes maintain same # of groups  Packet-driven forwarding [Zahemszky09]  Headers are replaced on domain border  Group size is greatly increased  Overhead on border can be distributed g1 n1:p2 n1:p3 … g1 n2:p1 … Headers table g1: n2:p1 … : g1: n2:p1 … : Domain border Packet-driven forwarding

11 Outline of assessment Takeru Network Innovation Labs.11  Multicast forwarding plane  Table-driven forwarding  Group # is limited by forwarding table size  Improved by virtual ports and Bloom filters  Packet-driven forwarding  Group size is limited by packet header size  Improved by virtual ports, Bloom filters, and hierarchy  Assessment  Scalability with regard to group number and group size  Forwarding performance  Control architecture  State management

12 Scalability on group number and size Takeru Network Innovation Labs.12  Target  Group # is > 1 T  Group size is < 1 M  Few large groups (Zipf distribution)  # of all nodes on delivery path

13 Scalability on group number and size Takeru Network Innovation Labs.13  Target  Group # is > 1T  Group size is < 1M  Table-driven forwarding  Group # is limited by table  Far less than 1T groups  1M with Bloom filters  More groups can be supported in overall network, but gap is too large  Packet-driven forwarding  Group size is limited by header  Group # of nearly 1M is supported  0.4M with all means # of groups at node (log-scale) Target 1M 410K Hierarchy Virtual ports and Bloom 640 1T Group size (log-scale) 6-order 1.8M Bloom Forwarding table: 18 Mbits Packet header: 800 bits K

14 Forwarding performance Takeru Network Innovation Labs.14  Table-driven forwarding  Performed in constant time by CAM other than with virtual ports  Repeated table lookup needed  Packet-driven forwarding  Performed in constant time with virtual ports and Bloom filters  Each physical port has TCAM  TCAM has virtual ports of the physical port  Bloom filter in packet is checked by all TCAMs in parallel  Packet is copied to all matched ports vp1 … p1: … p2: vp1 … p3: vp1 … p1: … p2: vp1 … p3: vp1 … p1 p2p3 TCAMs Set of virtual ports in Bloom filter vp1 Packet-driven forwarding Multiple elements in TCAM are checked against Bloom filter at once

15 Control architecture Takeru Network Innovation Labs.15  Table-driven forwarding  Follows distributed route computation  Joins are routed to a source and populate each hop with forwarding entries  Distributed computation complicates assurance of stable operation  Packet-driven forwarding  Follows central route computation  Source calculates delivery path and puts it in packet  Simple and stable  Doesn’t impose heavy load on sources, because each source calculates a few trees rooted at themselves  Port list (used to calculate delivery trees) is equivalent to OSPF link state or BGP AS path

16 State management Takeru Network Innovation Labs.16  Successful NW protocols  NW state is updated by trusted entities, because state failures can affect entire NW  Protocols not widely deployed  NW state is updated by users  e.g. IP multicast, MobileIP, and IntServ  Table-driven forwarding  Relies on joins by users  Violates requirements of successful protocols  Packet-driven forwarding  State (packet header) is created by source (trusted entity)  Meets requirements of successful protocols

17 Conclusions Takeru Network Innovation Labs.17  Taxonomy of multicast forwarding plane  Table-driven forwarding  Packet-driven forwarding (source routing)  Assessment of multicast forwarding plane  Future work  Quantitative analysis, control planes, and implementation issues Table-driven forwardingPacket-driven forwarding ScalabilityPoor in group #, good in sizeExcellent in group #, fair in size Forwarding performanceConstant time (no virtual ports)Constant time Control architectureDistributedCentral for each group (distributed for overall NW) State managementBy usersBy trusted entities

18 Creating mappings and packet headers in packet-driven forwarding Takeru Network Innovation Labs.18  Creating mapping of virtual ports  Creating packet header PortEntry vp1*1** 1*** vp2***1 ****1 :: TCAM at p p1 p2p3 vp h i (vp1) Add vp h i (vp3) Add vp h i (vp1) Add vp1 Zeros are converted into “don’t care bits” vp1 vp3 Filter is put on header


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