Hi Adrian -
Adrian Farrel wrote:
Just stepping back a moment...
It feels to me that we are getting drawn into discussions of what can and cannot be
achieved using existing protocols. This is all very valid, but is clearly not part of the
requirements work.
I understand that the DT wishes to analyse the changes to existing protocols to meet the
requirements under the charter phrase "to capture
what's missing from current CCAMP work", but I feel that this is clouding (and delaying)
the production of a clear requirements draft.
So looking at the three topics that Deborah raised.
1.
Some members of the Design Team noted that reachability information (as described in
Section 4.5.3) may be advertised as a set of UNI Transport Resource address prefixes
(assigned and selected consistently in their applicability scope). These members of the
Design Team raised a concern that existing methods of advertising reachability may need to
be examined (on a per-protocol basis) to determine if they are also applicable for UNI
Transport Resource addresses. They invite CCAMP discussion on this aspect.
The first sentence is about requirements.
Do we, or do we not, need to support advertising UNI Transport Resource address prefixes?
There is a requirement to be able to advertise reachability (G.7715 sec7.1.1, G.7715.1 sec
9.4). G.7715.1 states:
Reachability Information: Reachability information describes
the set of endpoints that are reachable by the associated node.
It may be advertised either as a set of UNI Transport Resource
addresses/address prefixes, or a set of associated
SNPP IDs/SNPP ID prefixes, the selection of which must be
consistent within the applicable scope.
so technically, there isn't a requirement to advertise UNI Transport Resource Addresses -- the
requirement is to advertise reachability in terms of SNPP IDs or UNI Transport Resources
Addresses.
It should be noted that there is a unique attribute of SNPP Prefixes and UNI Transport
Resource Addresses -- they exist independant of layer networks. More specifically, UNI
Transport Resource Addresses are used to name an Access Group Container, where the Access
Groups within the Container can be in one or more layer networks. So, it cannot be assumed
that a specific UNI Transport Resource Address is in Layer Network A or B.
The second sentence is about solutions and is not relevant in this draft.
2.
ASON does not restrict the architecture choices used, either a co-located architecture or
a physically separated architecture may be used. Some members of the Design Team are
concerned that GMPLS's concept of the LSR requires a 1-to-1 relationship between the
transport plane entity and the control plane entity (Router). They invite CCAMP input on
GMPLS capabilities to support multiple architectures i.e. how routing protocols would
identify the transport node ID vs. the router or routing controller ID when scoping Link
IDs in a link advertisement.
The first sentence is about requirements.
Do we, or do we not need to support a physically separated architecture with a 1-n
relationship between control plane and transport plane entities?
Yes.
The remaining text is about solutions and not relevant in this draft.
3.
In order to support operator assisted changes in the containment relationships of RAs, the
GMPLS routing protocol is expected to support evolution in terms of number of hierarchical
levels of RAs (adding and removing RAs at the top/bottom of the hierarchy), as well as
aggregation and segmentation of RAs. These GMPLS routing capabilities are considered of
lower priority as they are implementation specific and their method of support should be
evaluated on per-protocol basis e.g. OSPF vs IS-IS. In addition, support of non-disruptive
operations such as adding or removing a hierarchical level of RAs in or from the middle of
the routing hierarchy are considered as the lowest priority requirements. Note also that
the number of hierarchical levels to be supported is implementation specific, and reflects
a containment relationship e.g. a RA insertion involves supporting a different routing
protocol domain in a portion of the network.
Note: some members of the Design Team question if the ASON requirement for supporting
architecture evolution is a requirement on the routing protocol (protocol specific
capability) vs. a capability to be provided by the architecture. For example, ASON allows
for supporting multiple protocols within each RA. The multiple protocols share a common
routing information database (RDB), and the RDB is the component, which needs to support
architecture evolution. The Design Team invites CCAMP input to understand the
protocol-specific impacts.
This seems to mix up requirements and solutions.
It is not relevant what OSPF and IS-IS can or cannot do.
The requirements questions are:
A. What does ASON require in terms of evolution of hierarchies?
The requirements stated in G.7715.1 are:
"...the routing protocol shall be capable of supporting
architectural evolution in terms of number of hierarchical
levels, as well as aggregation and segmentation of RAs."
This is further illustrated as being:
- Segmentation of one Routing Area into two separate RAs
- Aggregation of two RAs into one RA
- Renaming of RAs
- Insertion of an RA into the hierarchy
- Deletion of an RA from the hierarchy
Insertion and Deletion can be done at any point in the hierarchy -- it is not limited to just
the top or bottom of the hierarchy.
B. Are these requirements immediate and high priority?
No statement of immediate/high priority exists in the ASON documents for any ASON requirement.