Network Heresy

[This post was written with Jesse Gross, Ben Basler, Bruce Davie, and Andrew Lambeth]

Tunneling has earned a bad name over the years in networking circles.

Much of the problem is historical. When a new tunneling mode is introduced in a hardware device, it is often implemented in the slow path. And once it is pushed down to the fastpath, implementations are often encumbered by key or table limits, or sometimes throughput is halved due to additional lookups.

However, none of these problems are intrinsic to tunneling. At its most basic, a tunnel is a handful of additional bits that need to be slapped onto outgoing packets. Rarely, outside of encryption, is there significant per-packet computation required by a tunnel. The transmission delay of the tunnel header is insignificant, and the impact on throughput is – or should be – similarly minor.

In fact, our experience implementing multiple tunneling protocols within Open vSwitch is that it is possible to…

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Assaf Muller

Where Am I?
Overview and East/West Traffic
Floating IPs

SNAT vs Floating IPs

A quick reminder about two NAT types used in Neutron.

  1. SNAT refers to source NAT, or, changing the source address of packets as they leave the external device of a router. This is used for traffic originating from VMs that have no floating IP attached. A router is allocated a single IP address from the external network which is shared across all VMs connected to all subnets the router is connected to. Sessions are differentiated according to the full tuple of (source IP, destination IP, source port, destination port). This is typically known as ‘PAT’, or port address translation in the networking world.
  2. Floating IPs, sometimes called DNAT (Destination NAT) in Neutronland, implement a much simpler form of NAT, a 1:1 private to public address translation. You can assign a VM a floating IP and…

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January 14, 2008

To be able to send information between two devices, both must speak the same language. This language is called the protocol.

The protocols that appear in the application layer of the TCP/IP model are:

  • File Transfer Protocol (FTP)
  • Hypertext Transfer Protocol (HTTP)
  • Simple Mail Transfer Protocol (SMTP)
  • Domain Name Service (DNS)
  • Trivial File Transfer Protocol (TFTP)

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TCP/IP Layers

January 14, 2008

The TCP/IP model defines four totally independent layers into which it divides the process of communication between two devices. The layers through which it passes information between two devices are:

TCP/IP Layers

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TCP/IP Model (Introduction)

January 14, 2008

TCP/IP was developed by the DoD (Department of Defense) of the United States and DARPA (Defense Advanced Research Project Agency) in the 1970s. TCP/IP was designed to be an open standard that anyone could use to connect computers together and exchange information between them. Ultimately, it became the basis for the Internet.

Basic Concepts of Network

January 14, 2008

1. Devices

In order to understand the explanation of protocols and ports, it is necessary for you to become familiar with the icons that represent the most common devices that are seen in the basic schemes. These are:

Network Devices

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