Forwarding in Content-Oriented Networks: Challenges and Probabilistic approaches

1. Forwarding in Content-Oriented Networks:Challenges and Probabilistic approaches Christian EsteveRothenberg University of Campinas (Unicamp) 05.12.10 - 08.12.10, Seminar 10492 Information-Centric Networking

2. Intro Back in early 2008: At University of Campinas, how to fast forward packets in content-oriented networks?

3. This Talk How to fast forward packets in content-oriented networks? • Goals of this discussion starter talk • Requirements and Challenges of forwarding (i.e., forward this packet to interface x?) on content identifiers (flat vs. structured) • Compact (probabilistic) approaches to forwarding:(approximate) network state vs. packet state • Non-goals • Routing (protocols, security, multipath), fwding strategies • Caching (only partly covered)‏ • Technology details (e.g., fast memory specs)

4. Content-Oriented Forwarding Requirements • Same as high speed packet switching... • High speed (i.e. Low lookup time) • 100Byte packets @ 10 Gbps -> 12.5 Mpps • Low storage • Amenable to hardware (e.g pipelined, memory BW, max pin number) • Low pre-processing time & Low update time

5. Content-Oriented Forwarding Challenges 32 (or 128) bit IP vs. Content IDs Higher than traditional packet switching... • High speed (i.e. Low lookup time) • 100Byte packets @ 10 Gbps -> 12.5 Mpps • Low storage • Amenable to hardware (e.g pipelined, memory BW, max pin number) • Low pre-processing time & Low update time + Line-speed cache support (pull/push) + (optional) signature verification

6. IP LPM vs. Content ID matching Content ID forwarding is challenging@ wire speed human machine

7. Fast Forwarding on Content Identifiers Content ID forwarding ischallenging@ wire speed Flat identifiers(e.g., 256-bit hash)‏ • Easy encoding • Fixed length • Non-aggregatable • Easy “exact” match lookup Structured identifiers(e.g., a/b/c/d:hash)‏ • Binary encoding (?) • Unbound length with non-fixed size components • Aggregatable • Costly “LPM” matching Need of content-oriented equivalents for fast forwarding algorithms (e.g., patricia trie, Lulea, tree bitmaps, etc.) ... think many year research on LPM for IP ... current work on security, DPI, NIDS, etc. E.g., transform forwarding into a signature matching problem? onerous task

8. Compact forwarding: A probabilistic approach Express the packet forwarding problem as two setmembership-problems solved with probabilistic data structures (Bloom-filter-inspired): • SPSwitch: Is packet label X in forwarding port P? • Approximate state in the network • Large Bloom filters maintained in forwarding • [Re-Arch08]tables • zFilters: Is outbound link A in packet header Z? • State in the packet header • Small in-packet Bloom filter representing a source route • [SIGCOMM09, Infocom11]

9. 4-dimensional solution space Transport efficiency (Stretch, Bandwidth) Routing / forwarding information in packets(packet header size) Multicast-readycompact forwarding packet routing Traditional unicast & compact routing State in network elements(FIB size) Adaptation costs(e.g., signaling)

10. SPSwitch forwarding engine [Re-Arch10] • model • implementation(FCF d-left hash Table) [Re-Arch08] • Is packet label X in forwarding port P? • Problem: Still O(n) entries

11. Publish/Subscribe Architecture: 3 Layers rendezvous layer establishes contact topology layer selects routes forwarding layer delivers data

12. iBFs: routable in-packet Bloom filters Statein the packet headers • Each network link has an identity and (a series of) Link IDs:Bloomed LID: 256 bit vector with just k=5 bit positions set to one • Forwarding on small, fixed size in-packet Bloom filter representing a source route • Formedbytopologyfunctionsorcollectedonpath (cf. IP switching) Basic operation “Is outbound link A in packet header Z?” • Small forwarding tables, very fast switching (bitwise AND operations) • Plus Extensions (Link ID Tags, virtual links, security, etc.) iBF = LID1 OR LID2 LID1 LID2

13. Stateless multicast with 256-bit zFilters (35 links -> approx. 20 subscribers) Enough for sparse multicast in typical WAN Practical results # Users Zipf distribution of multicast traffic # Groups stateful stateless

14. iBF forwarding 2.0 Frombasic [LIPSIN] toiBFonsteroids: • Secure self-routing capabilities [EC2ND] • AddressiBF replay attacks and empowerthe receiver. • Dynamic (keyed) computation of LinkIDsbasedon:In/Out interfaces, packetcontent, nodesecret K(t) • iBFsbecomeexpirable andcontent-dependent • Deletable [DlBF] • Compact bitmapheaderwithcollision-free regions • Loop-free • Per-hop permutations [Infocom11]

15. CCN forwarding

16. CCN with iBFs Attempt to solve the PIT state issue • INTEREST packets are forwarded based on FIB collect iBF back to the requester(s) Cache FIB iBF iBF PIT Interest 0100110 Interest 0000000 LID3 LID1 LID2 Link ID = Z (face in, face out, content ID, Ki(t) )

17. CCN with iBFs Attempt to solve the PIT state issue • INTEREST packets are forwarded based on FIB collect iBF back to the requester(s) • DATA packets are forwarded back to requester(s)based on the iBF Preserves flow symmetry, adds security, at the expense of BW efficiency Cache iBF Z-forw DATA 0100110 LID3 LID1 LID2 Link ID = Z (face in, face out, content ID, Ki(t) )

18. Compact forwarding in content-oriented networks Traditional Forwarding Compact Forwarding Scale by Synthetic aggregation (lossy compression) Moving (approximate) forwarding state to packets Trading state for over deliveries (flexible operation point) Probabilistic algorithms Trade correctness for space/memory time requirements Prone to one-sided errors (port-forwarding w/ extra packet dupls) Focus on multicast Receiver -oriented • Scaleby • Structuralaggregation(hierarchical IP) • Timelyinformation (Ethernet) • Deterministicalgorithms • Forward onlongestprefixes(Treebitmap IP lookup) • Exactlookupmatches(MPLS, Ethernet) • Focusonunicast • Sender-oriented

19. Conclusions • Forwarding on content identifiers is challenging • As in the past and in related engineering problems, probabilistic techniques represent an aid to the feasibility of routing on content labels via new space/time trade-offs • Still unresolved issue: Right balance between edge-, network- and packet state?

20. References C. Esteve Rothenberg, F. Verdi and M. Magalhães. “Towards a new generation of information-oriented internetworking architectures.” In ACM CoNext, First Workshop on Re-Architecting the Internet (Re- Arch08), Dec. 2008, Madrid, Spain. P. Jokela, A. Zahemszky, C. Esteve Rothenberg, S. Arianfar, and P. Nikander. “LIPSIN: Line SpeedPublish/Subscribe Inter-Networkings.” In ACM SIGCOMM’09, Aug. 2009, Barcelona, Spain. • Zahemszky, A. Császár, P. Nikander and C. Esteve Rothenberg. “Exploringthe Pub/Sub Routing& Forwarding Space.” In IEEE ICC, Workshop on the Network of The Future, Jun. 2009, Dresden, Germany. C. Esteve Rothenberg, P. Jokela, P. Nikander, M. Särela and J. Ylitalo. “Self-routingDenial-of-ServiceResistant Capabilities using In-packet Bloom Filters.” In 5th European Conference on Computer Network Defense (EC2ND), Nov. 2009, Milan, Italy. C. Esteve Rothenberg, C. A. Macapuna, F. L. Verdi and M. F. Magalhães. “TheDeletableBloomFilter: A new member of the Bloom family.” In IEEE Communication Letters, June 2010. C. Esteve Rothenberg, C. A. Macapuna, F. L. Verdi and M. F. Magalhães. “In-packetBloomfilters: Design and networking applications.” To appear in to Elsevier Computer Networks, March 2010.

21. References M. Särelä, C. Esteve Rothenberg, A. Zahemszky, P. Nikander and J. Ott. “BloomCasting: Security in Bloom filter based multicast.” In proceedings of the 15th Nordic Conference in Secure IT Systems (Nordsec) 2010, Aalto University, Espoo, Finland, 27-30 October 2010. M. Särelä, C. Esteve Rothenberg, T. Aura, A. Zahemszky, P. Nikander and J. Ott. “ForwardingAnomalies in BloomFilterBasedMulticast,” Submittedtothe 30th IEEE International ConferenceonComputerCommunications (IEEE INFOCOM 2011), 2011 SomayaArianfar, PekkaNikander, and JoergOtt, "On Content-Centric Router Design and Implications," in Workshop on Re-Architecting the Internet (ReArch 2010), an ACM CoNext workshop, Philadelphia, USA, November 30, 2010. Walter Wong and PekkaNikander, "Secure Naming in Information-Centric Networks," in Workshop on Re-Architecting the Internet (ReArch 2010), an ACM CoNext workshop, Philadelphia, USA, November 30, 2010. S. Tarkoma, C. Esteve Rothenberg and E. Lagerspetz. “Theory and Practice of Probabilistic Filters for Distributed Systems.” To appear in IEEE Communications Surveys and Tutorials, Fev. 2010.