C4

Question 1

computer networks: hub

Answer 1

sends out received data packet to all stations connected to it (floods packets to connected stations)

Question 2

computer networks: switch

Answer 2

learns to which ports certain stations are connected, so for a received packet it knows where to forward it (based on MAC address)

if it does not know the address, it floods the packet and learns

=> saves bandwidth and collisions

Question 3

computer networks: router

Answer 3

forwards data from one network to another based on their IP address

used to connect networks

Question 4

but how do we interconnect VMs running on a single physical computer?

Answer 4

• give each VM at least one virtual network interface
• all of these virtual interfaces are connected to an Ethernet bridge (a switch implemented in software)
• at least one physical network interface of the host is added to the bridge
  => all VMs have a path towards the physical network

Question 5

we want to have the ability to create virtual networks that are isolated from any other network created in the cloud. How?

Answer 5

Cloud vendors offer this as a service: you can create a private IP subnet and connect you VMs to his subnet (Virtual Internal Network)

Through cloud VPN you can connect physical office networks to this internal cloud environment

Question 6

VLAN

Answer 6

Virtual Local Area Network
allows you to create private and isolated networks on shared physical infrastructure (running on the same switch): separate network traffic without using routers

tag Ethernet packets with a VLAN number (to indicate the isolated network it belongs to)

Question 7

layer-3 switch

Answer 7

can also perform IP routing in addition to switching => eliminate the physical router

Question 8

SDN

Answer 8

Software-Defined Network
idea: separate data plane (hardware) and control p;ane (software controlling the hardware) => make hardware stupid

no longer run the control software on a small embedded processor within the network hardware

• move logic from software to hardware
• software computes and fills forwarding tables of hardware switches
• switches send encountered events to software and wait for orders
  => centralized control with global view

Question 9

SDN advantages

Answer 9

• virtualization: virtualize network resources to be able to lease these to multiple tentants
• performance: change flows when congestion is detected: dynamic bandwidth allocation
• QoS: provide guaranteed bandwidth to specific users by manipulating network paths
• energy efficiency: in case of low utilization, consolidate VMs on less servers, update network paths, turn off hardware => network elasticity

Question 10

NFV

Answer 10

Network Function Virtualization

implement network components (firewalls, load balancers, intrusion detection) in software and run in a virtual machine on commodity (server) hardware

Question 11

VXLAN

Answer 11

extends the number of supported virtual networks up to 16 million

we can even connect hypervisor hosts running Open vSwitch using VXLAN using switching hardware that does not support VXLAN

Question 12

OpenFlow

Answer 12

network protocol to allow controller and agents (switches) to communicate

controller updates flow table entries within the switches, switch can send information to controller (changes of port status)

Question 13

container orchestration

Answer 13

additional software to manage clusters of container hosts