LUF%20vs.%20LRF

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Title: LUF%20vs.%20LRF

1
LUF vs. LRF

2
Whats an LUF?

From Speermint-Terminology
The Look-Up Function (LUF) provides a mechanism
for determining for a given request the target
domain to which the request should be routed.
The question is what does target domain mean?
Option A terminating domain
Option B next-domain
Of course sometimes they are the same domain
Option C next-hop/next-trunk?
Note this isnt a question about what a specific
box does it can do LUF and LRF in one
transaction

3
Example 1 Bilateral peer
LUF
1
2
3
SSP-A
SSP-B

4
Example 1 The real world
SSP-A
SSP-B

Even bi-lateral peering in the real world is not
one trunk, not all trunks are created equal, and
it often depends on where the request came from

5
Why LUF answer is not next-hop

SF addressing is not static - they change due to
dynamic, temporary topology changes, or operator
control
SF address availability/reachability is not
global
SF addresses overlap - some SSP's use RFC-1918
addresses
SF addresses are private - many SSPs do not wish
to publish the SBE addresses they use for all
peering connections with all peers

6
Example 2 Transit peering
LUF
1
2
SSP-C
SSP-A
SSP-B
SSP-E
SSP-F
3

How do I get to b.com?
7
Why LUF is not next-domain

Transit SSP connections are not static
Transit SSP connections are not globally routable
- some SSP peering connections only service
direct bi-lateral traffic, while others are
usable for transit traffic but only for specific
regions or national codes
Transit SSP connection details are private
Loops can happen the LUF in subsequent domains
does not know the routing history of the request

8
So what is LRF?

1 Where is 1234567890?
2 ltsip1234567890_at_b.comgt
3 INVITE sip1234567890_at_b.com
LRF determines how to reach b.com
Currently through static provisioning (retrieved
on-box or through ENUM/SIP-redir queries)
Resulting SIP request example INVITE
sip1234567890_at_b.com SIP/2.0Route
ltsipsbe1.e.comlrgt
Or another, in request-urisip1234567890tgrpt
runk1.e.comtrunk-contexta.com_at_b.com

9
Why split them out?