Peer-to-peer, Point-to-point, and Beyond

Peer-to-Peer Networks

• Ad-Hoc communication is where you have a device, I have a device and we want to join them together. We don't have any network cable. So what we do is that we turn them on say: "I want to be my own network and become available for you", then you could find my network and our two devices would be talking to each other without any infrastructure at all. This is a very simple example of a peer-to-peer communication.

• A dedicated link between two sites would be called a peer-to-peer connection.

• Smaller business / homes

• Share resources with each other

  • File shares
  • Printers
  • Storage

• Easy to configure

  • Many times is right click on a folder -> share

• Not very scalable

  • If people connect how are they going to authenticate? File management?
  • The bigger it gets the more complex it is.
  • Hard to administer
  • Host is a Single Point of Failure (SPOF)
    • If I reboot my computer for a Windows update, everyone loses access to their files.
  • Performance concerns

• Used for small networks.

Point-to-Point Networks

• Two routers exchanging packets
  • "Every one on the Tampa office can talk to anyone in the Miami office"
  • This is a WAN link (two locations are very far from each other)
  • A dedicated circuit provided by an ISP.
• Network of two devices.
  • Host A and Host B
  • Only right and left IPs
• Leased lines comprised of digital circuits:
  • T1 - 1.544 Mbp
  • E1 - Europe equivalent to T1
  • T3 - 45 Mbp
  • E3 - Europe equivalent to T3
• All bandwidth is dedicated between sites
• Easy to configure and troubleshoot
• WAN links can be costly

Beyond

• Multi-point
  • More than one connections to remote sites
  • Typically a single interface circuit, for example a T1, would be configure logically so when we connect to the service provider we get 2 or more separate paths.
• Localhost
  • 127.0.0.1
  • If you sent a packet to this IP, that packet is going to yourself.
  • Good for local system communications
• Local system communications
  • You might have applications on your machine that are talking to one another
  • You may be able to see them listening on port numbers and they may bind to 127.0.0.1
  • Inter-Process Communications (IPC) go back and for over TCP port numbers.
• Tunnel Interface
  • 0.0.0.0/0
    • If you are going to anything with an IP address and you don't have a more specific match, come this way.
    • Also called the Gateway of Last Resort
  • If a packet is going to a specific IP destination specified inside our interface, I'll send that packet to my Tunnel Interface.
  • The Tunnel Interface has a configuration on it for how to transport the traffic to that specific destination.
    • As the traffic comes through our interface's router, it is encapsulated (we are adding a new header onto it), if we are using IPsec is ESP, and then we got typically an IP header.
    • Those new headers are used to get from our interface's router to the destination router.
    • Once the encapsulated packet gets to the destination's router, it looks and says "hey that's my IP address", it looks at the next header and says: "oh, that's ESP, that's for a VPN tunnel, I know how to decrypt all that". So it'll reach in and grab the original data, and then that original data will be sent into the inside network.
• Virtual Interface (Hot Standby Routing Protocol (HSRP))
  • We can have a switch that functions as the gateway for all our users.
  • We have a second switch that is the partner of the first switch, and basically say that if one switch is active, the other switch is standby.
    • If we got to reboot one of the switches so that we can do a software update for example, a message is sent over to the other switch and this device takes over and vice versa.
  • Could be used in a pair of switches or in a pair of routers.
    • Traffic flows through one and the other one is standby just watching.
  • This is classified as a first top redundancy protocol.
  • HSRP is Cisco's proprietary
  • Virtual Router Redundancy Protocol (VRRP) is standardized
  • Gateway Load Balancing Protocol (GLBP) provides redundancy as well as really intelligent load balancing.