Application Layer Traffic Optimization (ALTO)

Question 1

What is ALTO?

Answer 1

A standardized interface for the exchange of information between an underlying IP network and an overlay network(P2P).

This is done through a HTTP based client/server protocol.

Question 2

What is ALTO trying to solw?

Answer 2

1. Provide a definition for how P2P apps can be more network aware, and decide which endpoint to get data from
2. Reduce Service provide network congestion and costs due to random content fetching across networks
3. Better user experience, where users automatically get data from “Most Optimal” endpoint instead of fetching it randomly across globe

Question 3

What are ALTO use- cases?

Answer 3

• P2P apps(e.g. filesharing/video streaming)

- deployments in CDN and ISP networks for reduced latency, congestion and cost, also for better QoE and QoS.

Question 4

How does the ALTO server work?

Answer 4

HTTP REST- ful server deployed in the network.

Responds to queries from ALTO clients.

Maintains “my internet view” which is an allocation of:

• External Node Sets
• IntraDomain Node Set

Typically participates in routing protocol’s information exchange, accepts policy input from network mgmt. and data from monitoring systems to collect information.

Question 5

How does the ALTO client work?

Answer 5

Send queries to ALTO server, gets Query Cost Maps, uses the results to make peer gathering decisions.

Question 6

How does ALTO clients discover ALTO servers/services?

Answer 6

The network offers an “ALTO Service Discovery”, from which the ALTO client request Information Resource Directories(IRDs). The IRD response contains uris for the services available on the ALTO server as well as acceptable parameters.

Question 7

What does the HTTP query response from the ALTO server contain?

Answer 7

For instance a Network Map. A collection of possible endpoints in PID- groups. The client could then query for the cost of some of those endpoints in a new request and get a Cost Map.(via POST request)

Question 8

How does the ALTO client locate the ALTO service discovery?

Answer 8

the discovery domain might be directly configured, but usually the ALTO client obtains it via DHCP when joining a network.