Subject: RE: IPv6 Service Discovery

From: "Abhijit Chaudhary \(abchaudh\)" <[email-masked]>
Date: Thu, 4 Aug 2005 12:48:57 +0530

Hi John,
I think DHCP server is used to find TFTP server, time server, Gateway,
and maybe DNS too.
I don't think it can be used to find Printers or other video application
or VoIP server etc. 
Maybe a DHCP expert can comment more on it.
Generally DHCP server exist in the Service provider network, thus the
customer DHCP Request may have to go through a DHCP Relay agent to reach
the DHCP Server. Though DHCP server can also exist in the customer
network too.
Morever, in Stateless address configuration a DHCP server may not exist
too.

IMHO, I feel that address discovery and service discovery are separate
and best done by separate server for each.

- Abhijit 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] 
Sent: Thursday, August 04, 2005 12:22 PM
To: Abhijit Chaudhary (abchaudh); [email-masked]
Subject: RE: IPv6 Service Discovery

Abhijit,
 
What sort of Application Service are you talking about?  I know folks
look at using DHCP for configuring this kind of information, if I
understand you correctly.
 
John

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
ext Abhijit Chaudhary (abchaudh)
Sent: 04 August, 2005 08:23
To: [email-masked]
Subject: IPv6 Service Discovery

Hi,
I have question regarding IPv6 auto service discovery. 
 
Suppose a IPv6 Mobile Host comes and joins a network. Using Stateful or
Stateless Address Configuration mentioned in ICMPv6 Router
Advertisement message it gets a IPv6 address. 
But if the mobile host want to know the nearest printer IP address or
the proxy address or DNS server address (i.e, IP address of Responder
mentioned in draft-ietf-ipngwg-icmp-name-lookups-12.txt).
Is there any draft or RFC that talks about a procedure to get
information about Server providing application Service for IPv6?
 
If not, I am of the impression that we can add a new option to Router
Advertisement message called "Application Service Discovery Proxy". This
option will contain the IPv6 address and Link-Layer address of the
"Application Service Discovery Proxy". This proxy will contain all the
information of the available application service in the network and the
corresponding servers. The new option will look as below:
 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type         |    Length             |            Reserved
|  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           IPv6 Address of Application  Service Discovery Proxy
|
      +
|
      |  +++++++++++++++++++++++++++++++++++++++++++++++ |

      ~         Link-Layer Address of  Service Discovery Proxy
|   
      |
|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
The Message Exchange is described below:
 
1) Router Advertisement will contain the Application Service Discovery
Proxy Option
                                  "Router Advertisement with Application
Service Discovery Proxy Option"
                 Router
------------------------------------------------------------------------
---------------------------------------------------------> Host
 
2) Host gets the Address of the Application Service Discovery Proxy and
stores it. Suppose, the host wants printing service, it uses some
protocol (maybe UDP or XML over HTTP or ICMPv6) to discover services
from the Application Service Discovery Proxy.
    For Printing service the message as below:
                                        "Give me printer service
address" 
           1.     Host
------------------------------------------------------------------------
---------------->  Application Service Discovery Proxy 

"Printer IPv6 address = x, Printer LL address = y"
           2.     Application Service Discovery Proxy
------------------------------------------------------------------------
---------------------------> Host
 
                                           "Sends data to be printed" 
           3.     Host
----------------------------------------------------------------------->
Printer
 
Let me know what you guys feel about it.
 
Thanks,
- Abhijit

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---

From: Mohacsi Janos <[email-masked]>
Date: Thu, 4 Aug 2005 09:55:33 +0200 (CEST)

> I don't think it can be used to find Printers or other video application

I don't see any problem to configure these services via DHCP. 
Alternatively you could use SLP.

> Morever, in Stateless address configuration a DHCP server may not exist

Perfectly usable scenario is to use RA and SLAAC for configure 
addresses, gateway, link MTU etc. and stateless DHCP for DNS, NTP, 
potentially SIP servers...

> and best done by separate server for each.

Agree. Can you describe your scenario, where RA is more suitable for 
service discovery?

Regards,

Janos Mohacsi
Network Engineer, Research Associate
NIIF/HUNGARNET, HUNGARY
Key 00F9AF98: 8645 1312 D249 471B DBAE  21A2 9F52 0D1F 00F9 AF98