Network Architecture (R02) - L2 Jon Crowcroft,

Polyglot Networking There was a time before the Internet A long, long, long time ago… … … There were other protocol architectures too (gasp!) ISO, CCITT DECNET, XNS, SNA CR82, Color Book How to Interconnect?

Interworking different arch Application Layer Relay Transport Service Relay Protocol Translator Other? Future Nets Internet of Things (e.g. sensors) Space Networks

Delay Tolerant Networking Interplanetary Networking Delays (hours!) Disruption (solar flares!) Disconnections (eclipse!) What would “network” look like?

DTN Store, Carry, Forward Like an Net Also like UUCP (Usenet) Custodians Routing Predictable/Schedule (bus, train, spaceship, satellite) Random? Errors? FEC, Redundency?

For next week oct 22 You talk about ipmc (Ghao Gao) pgm (Natacha Crooks) All of you start to read/write about one of I3, IPNL, ROFL or ILNP See essay0.txt

Multicast - Classic Make the Internet one big Ethernet Steve Deering (w/ Dave Cheriton) 1988 New address (“Class D”) = Host Group, G Forwarding Scheme = away from S Prune/Graft per interface “towards” G Need (S,G) state, Per Router… State Management…

Group State Management Implicit Traffic Driven Explicit IGMP Driven More Overheads! So not only state overhead is S*G But also control overhead O(G) messages Aggregation probably doesn’t do much Any Source v. Source Specific v. Single

Single Source Can use reverse path fwd only Can auth/check source (exactly same as Best Practice RPF check) Not much use for many-to-many apps? N.b. looking at main early use of multicast (“mbone”) - was many-to-many video conf main use now? IPTV, Radio, S/W

Reliable Multicast Seems to be no “one size fits all” Nack, Ack Aggr & Code based schemes Need various ordering semantics (if n-m) Interesting e.g. of new style WG in standards Did “building blocks” Then composed RM protocols from these One v. interesting idea - GRA minimal router processing engine needed for e2e protocol support Precursor of other middle box ideas…

RM - Congestion Control & Failures Two things hard to define How should multicast flow “compete” with TCP? What are the “late join”, “early leave” and “fail” semantics for some members? Again, no “one size fits all” answer…

The “Truth” about Multicast In fact, in a conference in 2006 Berkeley Sys Admins reported that Turning on IP multicast broke Unicast! Classic deployment dilemma Specially Bad Case Multicast has to be in “fast path” Multicast routing depends closely on Unicast (viz PIM) It also depended on monitoring data to drive routing update So new control plane interface to fast path :-(

For next week - oct 22 2 of you talk about Deployment Issues for IP Multicast & Pragmatic Generalized Multicast All of you read the two papers See Don’t forget…for nov 2 essay0.txt