notes/docs/lectures/acn/08_content_centric_networks.md

Content-Centric Networks

A Brief History of Networking

• Gen 1. The phone system (focus on the wires)

  • The utility of the system depends on running wires to every home & office.

  • Wires are the dominant cost.

  • A call is not the conversation; it's the PATH between two end-office line cards.

  • A phone number is not the name/address of the caller; it's a program for the end-office switch fabric to build a path to the destination line card.

  • 

  • Path building is non-local and encourages centralisation and monopoly.

  • Calls fail if any element in the path fails, so reliability goes down exponentially as the system scales up.

  • Data cannot flow until the path is set up so efficiency decreases with setup time.

• Gen 2. The Internet (focus on the endpoints)

  • Data sent in independent chunks and each chunk contains the name of the final destination.
  • Nodes forward packets onward using routing tables.
  • ARPAnet was built on top of the existing phone system.

• Gen 3. dissemination (focus on the data)

TCP/IP

Pros

• Adaptive routing lets system repair failures
• Reliability increases exponentially with system size.
• No call setup means high efficiency at any bandwidth and scale.
• Distributed routing supports any topology and tends to spread load and avoid a hierarchy's hot spots.

Cons

• Connected is a binary attribute.
• Becoming part of the internet requires a globally unique, globally known IP address that's topologically stable on routing time scales.
  • Connecting is a heavyweight operation
  • The net struggles with moving nodes

Conversation and Dissemination

Acquiring chunks of data (web pages, emails, videos etc) is not a conversation, it's dissemination.

In a dissemination the data matters, not the supplier.

• Data is requested by name.
• Anything that hears the request, and has a valid copy can respond.
• The return data is signed, so integrity and association can be validated.

CCN can run over and be run over anything e.g. IP.

CCN Packets

Interest - similar to HTTP GET

Data - similar to HTTP response

Content Based Security

Data packets are authenticated with digital signatures.

CCN Forwarding

The consumer broadcasts an interest over all available communication media.

• e.g. get '/parc.com/van/presentation.pdf'
• response: heres '/parc.com/van/presentation.pdf/p1' <data>

Names and Meaning

• Like IP, CCN nodes impose no semantics on names
• Meaning comes from application, institution and global conventions reflected in prefix forwarding rules.
• Globally meaningful name leveraging the DNS global naming structure
  • /parc.com/van/presentation.pdf
• Local and context sensitive, it refers to different objects depending on the room you're in.
  • /thisRoom/projector

Strategy Layer

• When you do not care who you are talking to, you don't care if they change
• When you are not having a conversation, there's no need to migrate conversation state.
• Multi-point gives you multi-interface for free.
• When all communication is locally flow-balanced, your stack knows exactly what's working and how well.

In the current Internet, Quality of Service (QoS) Problems are highly localised

• Roughly half the problems are from serial dependencies created by queues
• The other half are caused by a lack of receiver-based control over bottlenecked links.

Unlike IP, CCN is local, doesn't have queues, and gives receivers complete control.

Tree serves as transport state