This document defines the topology naming conventions that are to be
used in reference to IEPREP phone calls. These naming conventions
should be used to focus the IEPREP Working Group (WG) during
discussions and when writing requirements, gap analysis and other
solutions documents.
There has been much confusion on the IEPREP list as well as within
each meeting about the topologies IEPREP is considering. Hopefully
this document will give each reader and author a reference set of
named architectures.
This memo attempts to be agnostic with regard to IP signaling or
control protocols (SIP, MEGACO, etc), as well as any underlying
Quality of Service (QOS) mechanisms (Diffserv, RSVP, NSIS, etc).
Simply put, to get everyone referencing the same (named) topologies
in order to have useful and less confusing dialog to further this
working group's efforts.
There are 4 often mentioned, but very little documented topologies
discussed within this WG's efforts so far. The following subsections
name and describe each of the topologies.
The 4 topologies are (quickly):
Topology "IP Bridging"
Topology "IP at the Start"
Topology "IP at the End"
Topology "End-to-End IP"
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RFC 3523 IEPREP April 2003
This topology is sometimes known as "IP in the Middle" of two CSNs.
In this topology, a CSN phone of any type initiates (dials) a call to
another CSN phone with an IP core between the two CSNs.
This topology should simplistically look like this:
Circuit Internet Circuit
Switched IP or IP Switched
Network Ingress IP Segment Egress Network
-----------+ +--------------+ +-----------
| +----+ | IP | +----+ |
CSN | | | | | | | | CSN
Phone ------->| GW |----------------------->| GW |-------->Phone
| | | | | | | |
| +----+ | | +----+ |
-----------+ +--------------+ +-----------
Figure 1. Topology "IP Bridging"
This topology has the initiating party placing (dialing) the call
from an IP Phone (PDA or computer), and the called party residing in
the CSN.
Internet Circuit
or CSN Switched
IP Segment Ingress Network
-------------------+ +---------------
| +----+ |
IP | | | | CSN
Phone ------------------>| GW |--------> Phone
| | | |
| +----+ |
-------------------+ +---------------
Figure 2. Topology "IP at the Start"
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RFC 3523 IEPREP April 2003
This topology has the calling party placing the call from a CSN
phone, and the called party being in an IP network.
Circuit Internet
Switched CSN or
Network Egress IP Segment
-------------------+ +---------------
| +----+ |
CSN | | | | IP
Phone ------------------>| GW |--------> Phone
| | | |
| +----+ |
-------------------+ +---------------
Figure 3. Topology "IP at the End"
This topology has no circuit switched sections in the call path.
Internet
or
IP Network
+-----------------------------------------+
| |
+---------+ +-----------+
| |
| IP IP |
| Phone --------------------------------------------> Phone |
| |
+---------+ +-----------+
| |
+-----------------------------------------+
Figure 4. Topology "End to End IP"
Although shown as one large IP cloud here, the Internet is composed
of a series of loosely connected IP domains. An End-to-End IP call
will likely traverse a number of these domains and/or multiple
network providers, which may impact the call.
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RFC 3523 IEPREP April 2003
James M. Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082 USA
EMail: jmpolk@cisco.com
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RFC 3523 IEPREP April 2003
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