This presentation describes the concept of zero configuration by explaining the bonjour protocol.

1. BONJOUR
Prepared for
Prof. Kaewon Choi
By
Salah Amean Ahmmed

2. INTRODUCTION
 IP like electricity or water
 Just plug and it work
 Bonjour is truly revolutionary,
 it is one of the things that is going to have the
largest impact on application designing over the
next couple of years.

3. BACKGROUND
 Bonjour is Apple’s implementation of a suite of
zero-configuration networking protocols.
 Bonjour is designed to make network
configuration easier for users. For example,
Bonjour lets you connect a printer to your
network without the need to assign it a specific
IP address or manually enter that address
into each computer
 With zero-configuration networking,
 Nearby computers can discover its (printers)
existence and automatically determine the printer’s
IP address
 They can automatically discover the new address in
the future even when changes happen

4. BACKGROUND
 Apps can also leverage Bonjour to automatically
detect other instances of the app (or other
services) on the network.
 For example, two users running an iOS photo
sharing app could share photos over
 Bluetooth personal area network without the need to
manually configure IP addresses on either device

5. WHY BONJOUR?
 The transition from platform-specific
protocols(AppleTalk) to IP happened over the
past two decades
 Currently computers and other network devices
all use TCP/IP for communication.
 In that transition, however, one piece of
functionality was lost
 the ability to add devices to a local network
and then connect to those devices from
computers and other devices on the network, all
with little or no configuration.

6. CONCEPT
 For IP to work, devices need to be assigned addresses
either manually or dynamically(DHCP).
 A dynamically assigned address can change,
 Without Bonjour,
 Printers and other devices had to be manually
configured with a static address so that computers on the
network could reach them.
DNS server has to be configured so that computer
users didn’t have to connect to the printer by IP
address.
 Thus, a seemingly minor task required significant
configuration.
 Sometimes it isn’t practical to have complicated
configuration for minor tasks such as printing a paper

7. CAPABILITY OF BONJOUR
 Without wasting people time to get configuration
done, people should be to be able to
 plug in the printer,
 plug two laptops together, or
 look for a file server or game server on the local network
 To support this, people need a simple and reliable
way to configure and browse for services over IP
networks.
 User want to discover available services and
 Choose one from a list, instead of having to know
each service’s name or IP address in advance.
 It is in everyone’s interest for IP to have this
capability

8. ZERO CONFIGURATION: AN
EXAMPLE
 In step 1, you open up your laptop in your
neighbor’s house, and the laptop either
 Obtains an address from DHCP server in the router
or,
 In the absence of a DHCP server, assigns itself an
available local address
 In step 2, the network is queried for available
printers so that
 when you open the Print dialog, your neighbor’s
printer is listed
 In step 3, you turn on music sharing on your
computer, and your neighbor’s computer sees it
and connects.

9. ZERO CONFIGURATION: AN
EXAMPLE

10. ZERO CONFIGURATION: AN
EXAMPLE

11. WHAT IS ZEROCONF NETWORK?
 No external supporting infrastructure
 No manual configuration
 No (conventional)DHCP Server
 No conventional DNS server
 Limited Network Scope
 Not too many users
 Not too many hosts;
 Simply by connecting two laptops using
Ethernet cable

12. THREE LEGS OF BONJOUR
 Addressing : address is need to identify host on
the network
 Naming: using names instead of the IP address
 Browsing: we need to discover what is in the
network.

13. ADDRESSING
 Self-Assigned Link-Local Addressing
 Pick random address in 169.254/16
 Claim this address by ARP
 ARP to see if anyone else is using it
 if someone else is using it, try again
 ongoing conflict checking
 Http://www.zeroconf.org/
 One of the important issues regarding this sort of
addressing is that they are meant for local usage only
typically a small LAN or a single LAN segment
 For example when we print a document from host A
to a host B on the local network, then this addressing
scheme is sufficient

14. IPV4 LINK-LOCAL AVAILABILITY
 Self-Assigned IPv4 Link-local Addressing
 first appeared in
 Mac OS8.5,1998
 Windows 98, 1998
 Mac OS X 10.0
 IPv6 already has link-local addressing
 This is not to compete with it but to encourage apps to
support IPv6
 But low cost devices that has no support for IPv6
 Major operating systems supports local link
addressing
 Hardware manufacturers should implement link-local
addressing on their devices to obtain the full benefit
of Bonjour.

15. ADDRESSING WITH ZEROCONF
 Device that supports link-local addressing
benefits from this feature automatically.
 When your host computer encounters a local
network,
 it finds an unused local address and
 adopts it.
 No action on your part is required.

16. NAMING
 Multicast DNS is the proposed solution to the
translation of name-to-address on local networks
 Because these DNS queries are sent to a
multicast address,
 no single DNS server with global knowledge is
required to answer the queries.
 Each service or device can provide its own DNS
capability
 when it sees a query for its own name,
 it provides a DNS response with its own address.

17. NAMING AND RESPONDER
 Responder handles mDNS queries for any
network service on the device
 This daemon takes charge of interpreting mDNS
queries and multicast messages
 Automatically advertises the availability of your
service
 so that any queries for your name are directed to
the correct IP address and port number
automatically.

18. NAMING
 Uniqueness of names is essential for name-to-address
to work properly
 Names in bonjour have local significance only
 Pick desired name in ".local."subdomain
 Issue Query to see if anyone else is using it
 if someone is else already using it, pick another
 ongoing conflict checking

19. NAMING EXAMPLE
 A printer with the default name XYZ-LaserPrinter.
local to Local network.
 XYZ-LaserPrinter.local, then XYZ-LaserPrinter-
2.local,
 XYZ-LaserPrinter-3.local is unused,thus becomes
the name
 Bonjour renames automatically

20. BROWSING
 “what we want to do?” is to just browse what is
inside the network rather just type is in the
browser some numbers or names
 Long list of attempts allows automatic detection
of devices/services on networks
 RLP (resource location protocol)
 SDP (Service discovery protocol)
 SSDP (Simple service discovery protocol)
 SDS Service discovery services

21. DEVICE-CENTRIC VS. SERVICE
CENTRIC
 In device centric
 A client queries to the server, and checks what is
available on the server
 Server responds with list of running
service( HTTP, ftp, etc.)
 Digging inside the server for some relevant
information
 Decides what services to use
 The Response:
 May not be exactly what the user needs
 Cause a lot of unneeded network traffic

22. DEVICE-CENTRIC VS. SERVICE
CENTRIC
 In service centric:
 It makes more sense to query for “What print
services are available?” than
 “what services are you running” then go though
list of available services
 In this scheme, a single query produce only
relevant replies
 Services are not tied to specific IP addresses or
even host names (e.g., load-balancing situation)
 Queries are made according to the type of service
needed, not the hosts providing them

23. SERVICE DISCOVERY
 Service discovery in Bonjour is accomplished by
“browsing.”
 An mDNS query is sent out for a given service,
type and domain
 Any matching services reply with their names
 The result is a list of available services to choose
from.

24. BONJOUR SERVICE DISCOVERY
 Bonjour takes the service-oriented approach.
Queries are made according to the type of service
needed, not the hosts providing them.
 Applications store service instance names, not
addresses, so if the IP address, port number, or
even host name has changed, the application can
still connect.
 User’s browsing experience is made more useful
and trouble-free.

25. SERVICE DISCOVERY ADVANTAGES
 Allows applications to find all available instances
of a particular type of service and
 To maintain a list of named services and port
numbers
 So with changes, effect won’t hurt

26. SERVICE DISCOVERY EXAMPLE

28. PUBLISHING A SERVICE

29. PUBLISHING A SERVICE-CONT’

30. ADVERTISING SERVICES
 Applications provide a service name and port
 follows same DNS specific to general model
 ServiceName._ServiceType._TransportProtocolN
ame.Domain
 ServiceName is human readable descriptive
name
 Maximum of 63byte
 All characters are allowed
 HP officeJet8500._ipp._tcp.local.
 service name is HP officeJet8500
 services type(internet printing protocol) is ipp
 Transport Protocol is tcp
 Domain is .local

31. CHALLENGES

32. SOLUTION
 Caching
 mDNSresponder takes charge of caching,
 Some requests are kept to the time of need
 Suppression of duplicate responses
 Back-off

33. CHALLENGES

35. BONJOUR BONJOUR GATEWAY
DEMO
 http://www.youtube.com/watch?v=i8vNlqV67uA

36. DEMO LAB310

38. REFERENCES
 https://developer.apple.com/library/mac/documentation/cocoa/conc
eptual/NetServices/Articles/NetServicesArchitecture.html
 http://www.zeroconf.org/QDIPv4LL.html
 http://www.youtube.com/watch?v=pdbTyxYmF84
 http://www.ietf.org/rfc/rfc3927.txt
 http://www.aerohive.com/solutions/technology-behind-solution/
bonjour-gateway
 http://blogs.enterasys.com/apple-bonjour-devices-in-the-enterprise-
part-1/
 http://en.wikipedia.org/wiki/Zero-configuration_networking