1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER
DCN: srho-sff-discovery-discussion
Title: SFF Discovery Discussion
Date Submitted: September 14, 2010
Presented at IEEE Session #40, St. Petersburg
Authors or Source(s):
 Hongseok Jeon, Junghoon Jee, Changmin Park (ETRI)
Abstract: Summary of teleconference discussion about how to discover the nearest and suitable SFF to the given query.

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3. 21-09-0193-00-srho-sff-discovery-discussion
Background
21-10/131r3 (IEEE c Proposal) presented new Information Elements for SFF.
IE_SFF_TUNN_MGMT_PRTO
IE_SFF_FQDN
One issue was raised due to the fact that SFF has no physical location information.
How can Information Server discover the nearest and meaningful SFF for the given querier?
There were discussions about how to discover a suitable SFF in last 21c teleconferences.
Approach 1: Using TLV query parameters (DCN: 21-10/164r0)
Approach 2: Using enhanced DNS server (DCN: 21-10/168r0)
srho-sff-discovery-discussion

4. Approach 1: TLV Query Parameters
In IEEE Std , a TLV query can include the optional parameters to refine the query response.
NET_TYPE_INC
NETWK_INC
We need a more detailed parameter.
Given NET_TYPE_INC and NETWK_INC might provide information on multiple SFFs than a specific SFF suitable to a querier.
Specific PoA can be a meaningful parameter in the TLV query whereby IS retrieves information on the SFF specific to given query.
POA_INC: Target (or Serving) PoA the queirier wants to include in the query response.
Information Server can respond with suitable information (IE_SFF_TUNN_MGMT_PRTO, IE_SFF_FQDN) on SFF matching the preferred PoA.
NET_TYPE_INC: network types the querier wants to include in the query response.
NETWK_INC: specific network the querier wants to include in the query response.
srho-sff-discovery-discussion

5. Approach 2: Enhanced DNS Server
In the configuration that one domain name may give multiple IP addresses, DNS can be used to find suitable IP address.
This method is an already deployed method and includes load-balancing, round-robin, and longest-match rules.
For example, when user types in the browser, DNS system will return the nearest yahoo server to the user.
It may be possible to apply this method to the discovery of the nearest SFF.
The longest matching method is already used in many other scenarios.
It applies longest match to the source IP address, so we can assume that the longest match IP address is the nearest SFF.
There is then no need for the MN to provide its location information.
srho-sff-discovery-discussion