Hi all,
As part of the ongoing effort to expose attachment circuits as a service, we
figured out that there is a need to clearly separate the notions of "attachment
circuits" vs. "bearers" and clearly identify the physical setup vs. required
properties over that layer to actually be able to exchange data. The current
use of these terms in existing RFCs [1] may be perceived as inconsistent. We
are currently discussing (AC Definition Pull Request #32 ·
boucadair/attachment-circuit-model<https://github.com/boucadair/attachment-circuit-model/pull/32/files>
and bearer definition Pull Request #26 · boucadair/attachment-circuit-model
(github.com)<https://github.com/boucadair/attachment-circuit-model/pull/26/files>)
to define these two concepts.
However, Bo raised a comment about the AC definition in draft-ietf-opsawg-sap:
The suggestion distinction between bearer and AC is nullified if we also accept
that AC covers the physical link. In order to avoid that confusion, I suggest
we make this simple change to draft-ietf-opsawg-sap:
===
OLD:
Attachment Circuit (AC): A channel that connects a Customer Edge
(CE) to a Provider Edge (PE). The AC may be a physical or logical
link (Section 6.1 of [RFC4026]).
NEW:
Attachment Circuit (AC): A channel that connects a Customer Edge
(CE) to a Provider Edge (PE).
===
Unless there are objections, I will propose this change during AUTH48 of the
SAP draft.
Thank you.
Cheers,
Med
[1]: Excerpts from the existing RFCs.
RFC4026:
In a Layer 2 VPN the CE is attached to PE via an Attachment Circuit
(AC). The AC may be a physical or logical link.
RFC4364 (L3VPN):
Routers can be attached to each other, or to end systems, in a
variety of different ways: PPP connections, ATM Virtual Circuits
(VCs), Frame Relay VCs, ethernet interfaces, Virtual Local Area
Networks (VLANs) on ethernet interfaces, GRE tunnels, Layer 2
Tunneling Protocol (L2TP) tunnels, IPsec tunnels, etc. We will use
the term "attachment circuit" to refer generally to some such means
of attaching to a router. An attachment circuit may be the sort of
connection that is usually thought of as a "data link", or it may be
a tunnel of some sort; what matters is that it be possible for two
devices to be network layer peers over the attachment circuit.
RFC4646 (L2VPN):
In any type of L2VPN, a CE device attaches to a PE device via some
sort of circuit or virtual circuit. We will call this an "Attachment
Circuit" (AC). We use this term very generally; an Attachment
Circuit may be a Frame Relay DLCI, an ATM VPI/VCI, an Ethernet port,
a VLAN, a PPP connection on a physical interface, a PPP session from
an L2TP tunnel, an MPLS LSP, etc. The CE device may be a router, a
switch, a host, or just about anything, which the customer needs
hooked up to the VPN. An AC carries a frame between CE and PE, or
vice versa.
RFC8299 (L3SM):
A "site" is composed of at least one "site-network-access" and, in
the case of multihoming, may have multiple site-network-access
points. The site-network-access attachment is done through a
"bearer" with an "ip-connection" on top. The bearer refers to
properties of the attachment that are below Layer 3, while the
connection refers to properties oriented to the Layer 3 protocol.
The bearer may be allocated dynamically by the SP, and the customer
may provide some constraints or parameters to drive the placement of
the access.
RFC8466 (L2SM):
A site contains at least one network access (i.e., site network
accesses providing access to the sites, as defined in Section 5.3.2),
and there may be multiple network accesses in the case of
multihoming. Site-to-network-access attachment is done through a
bearer with a Layer 2 connection on top. The bearer refers to
properties of the attachment that are below Layer 2, while the
connection refers to Layer 2 protocol-oriented properties.
RFC9291 (L2NM):
Similar to Section 3 of [RFC8466], CE to PE attachment is achieved
through a bearer with a Layer 2 connection on top. The bearer refers
to properties of the attachment that are below Layer 2, while the
connection refers to Layer 2 protocol-oriented properties.
RFC9182 (L3NM):
A site, as per [RFC4176], represents a VPN customer's location that
is connected to the service provider network via a CE-PE link, which
can access at least one VPN. The connection from the site to the
service provider network is the bearer. Every site is associated
with a list of bearers. A bearer is the Layer 2 connection with the
site.
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