Internet DRAFT - draft-zpm-dmm-mup-bgp-signaling
draft-zpm-dmm-mup-bgp-signaling
dmm Z. Zhang
Internet-Draft Juniper Networks
Intended status: Standards Track K. Patel
Expires: 8 September 2022 Arrcus
S. Matsushima
Softbank
7 March 2022
BGP Signaling for Mobile User Plane
draft-zpm-dmm-mup-bgp-signaling-00
Abstract
This document specifies BGP signaling for router-based 5G User Plane
using Mobile User Plane SAFI and some of its route types as specified
in [draft-mpmz-idr-mup-safi].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 September 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Zhang, et al. Expires 8 September 2022 [Page 1]
Internet-Draft BGP Signaling for MUP March 2022
Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminologies . . . . . . . . . . . . . . . . . . . . . . 3
2. Analysis of SRv6 specific aspects of
[I-D.mpmz-dmm-mup-safi] . . . . . . . . . . . . . . . . . 3
2.1. BGP Discovery Direct Route . . . . . . . . . . . . . . . 3
2.2. BGP Discovery Interwork Route . . . . . . . . . . . . . . 3
3. Optional Type 3 Session Transform (ST3) Route . . . . . . . . 4
4. Specifications . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. BGP Encodings . . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. GTP PW Label Extended Community . . . . . . . . . . . 5
4.1.2. Type 3 Session Transform (ST3) route . . . . . . . . 5
4.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Background
5G [_3GPP-23.501] User Plane uses N4 signaling between Session
Management Function (SMF) and User Plane Function (UPF), and N2
signaling between Access & Mobility Management Function (AMF) and
Access Nodes (AN). A traditional UPF device is typically centrally
deployed and uses GTP tunnels between itself and ANs for data traffic
to/from User Equipment (UEs). The GTP tunnels are set up by the N4
and N2 signaling, and the forwarding model on a UPF is quite
different from that on a typical router.
UPFs can also be deployed in distributed fashion and still provide
persistent IP address for UEs if needed, as described in
[I-D.zzhang-dmm-5g-distributed-upf].
Some operators may desire to deploy UPFs that are implemented more
like a router with BGP instead of N4 signaling. GTP tunneling can
still be used or it can be partially replaced by SRv6/MPLS tunneling.
It does not require any change to the 3GPP architecture, signaling
and deployment model, but a controller is used to convert N4
signaling to BGP, as described in [I-D.mhkk-dmm-srv6mup-architecture]
and [I-D.mpmz-dmm-mup-safi].
The above two drafts are both SRv6 specific. However, BGP signaling
from the controller based on N4 signaling can be done without being
SRv6 or even SR specific at all. This document specifies
corresponding BGP signaling and procedures for both central and
Zhang, et al. Expires 8 September 2022 [Page 2]
Internet-Draft BGP Signaling for MUP March 2022
distributed deployment models with integration with wireline VPN
services as described in [I-D.zzhang-dmm-5g-distributed-upf],
[I-D.mhkk-dmm-srv6mup-architecture], and [I-D.mpmz-dmm-mup-safi].
1.1. Terminologies
Terminologies of 5G, or those used in [I-D.mpmz-dmm-mup-safi] and
[I-D.mhkk-dmm-srv6mup-architecture] are omitted here for now. It is
expected that audience of this document are familiar with them or can
refer to the relevant documents.
2. Analysis of SRv6 specific aspects of [I-D.mpmz-dmm-mup-safi]
The goal of this document is to specify encoding and procedures that
work for both MPLS, SR-MPLS as well as SRv6. Therefore, we first
look at the SRv6 specific aspects of [I-D.mpmz-dmm-mup-safi].
2.1. BGP Discovery Direct Route
Per [I-D.mpmz-dmm-mup-safi]:
"The Discovery Direct route is generated by the MUP PE when a routing
instance accommodates a Direct type MUP Segment, e.g., N6 interface or
routes on DN side in 3GPP 5G specific case. It generates the
Discovery Direct Route per each routing instance for the MUP Segment."
When a MUP GW receives a BGP Type 2 Session Transform (ST2) Route,
which advertises the association of PDU Session TEID (on the UPF
side) and a DN VPN, a corresponding Direct Route is matched to set up
forwarding state on the GW so that it can decapsulate incoming GTP
packets from gNB/AN and then send to the advertising MUP PE of the
Direct Route using the Prefix SID in the Direct Route. The Prefix
SID has an End.DT2/4/6 or End.DX2/4/6 behavior.
In the non-SR case (and SR-MPLS or SRv6 as well), this route can be
replaced by the "VPN-IP default route" in [RFC7024]. The VRF table
label in the route is used to send traffic by the GW to the MUP PE
after GTP decapsulation.
2.2. BGP Discovery Interwork Route
Per [I-D.mpmz-dmm-mup-safi]:
Zhang, et al. Expires 8 September 2022 [Page 3]
Internet-Draft BGP Signaling for MUP March 2022
"The Discovery Interwork route is generated by the MUP GW when a
routing instance accommodates an Interwork type MUP Segment, e.g., N3
interfaces or routes on RAN side in 3GPP 5G specific case. It
generates route per each N3RAN IP prefix and stores the route in the
routing instance of N3RAN. The IP prefix MAY include a gNodeB
address which is connecting to the MUP GW."
Basically, it is a route for a gNB/AN address in the N3RAN. These
routes are put into N3RAN RIB. When a MUP PE receives a BGP Type 1
Session Transform (ST1) route, the Endpoint Address in the ST1 NLRI
is resolved in the N3RAN RIB, and the Prefix SRv6 SID associated with
the Interwork Route, which has the End.GTP4/6.E behavior on the GW,
is used send DownLink (DL) traffic from the MUP PE towards the gNB/AN
via the GW.
In the non-SR case (and SR-MPLS or SRv6 as well), this route can
simply be replaced with a regular host route for the gNB/AN. In case
of MPLS or SR-MPLS, an "IP/UDP Payload PseudoWire"
[I-D.zzhang-pals-pw-for-ip-udp-payload] label for GTP is encoded in
an Extended Community so that the MUP PE can use it to send DL
traffic with GTP encapsulation but w/o IP/UDP header to the GW, who
will add the IP/UDP header and send the resulting GTP packet to the
gNB/AN.
The PW label is encoded in an EC because only the DL traffic should
use the PW label and other traffic towards the gNB/AN should not.
In case of SRv6, the same Prefix SID that would be attached to the
Interwork Segment route can be attached to the regular gNB/AN host
route that replaces the Interwork Segment route.
3. Optional Type 3 Session Transform (ST3) Route
In [I-D.mpmz-dmm-mup-safi], the ST1 route only has the TEID and
endpoint address for the gNB/AN side for DL traffic. For UpLink (UL)
traffic, the ST2 route has the TEID prefix and endpoint address for
the UPF side, so that the GW can determine which DN the traffic
belongs to.
It is quite possible that the TEID assigned by the SMF are per-
session and do not fall into prefix ranges nicely. Unless the MUP
controller intelligently aggregate individual per-session ST2 routes,
a MUP GW that also acts as a MUP PE will receive individual per-
session ST1 and ST2 routes. For that reason, an optional ST3 route
is introduced to combine ST1 and ST2 routes.
4. Specifications
Zhang, et al. Expires 8 September 2022 [Page 4]
Internet-Draft BGP Signaling for MUP March 2022
4.1. BGP Encodings
A Type 3 Session Transform (ST3) route, and a GTP PW Label Extended
Community are specified in this section.
4.1.1. GTP PW Label Extended Community
The GTP PW Label Extended Community is a BGP MUP Extended Community
of sub-type "GTP PW Label" (value to be assigned by IANA).
The encoding is as following:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=MUP EC | Sub-Type=TBD | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved=0 | GTP PW Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1.2. Type 3 Session Transform (ST3) route
A new Route Type for BGP-MUP NLRI is added:
+ 5 - Type 3 Session Transform (ST3) route;
It is similar to the ST1 route:
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Prefix Length (1 octet) |
+-----------------------------------+
| Prefix (variable) |
+-----------------------------------+
| Architecture specific (variable) |
+-----------------------------------+
For 3gpp-5g, the Architecture Specific part of the NLRI encodes the
<UPF Address, UPF TEID, AN Address, AN TEID, QFI> parameters of the
session that the route is for:
Zhang, et al. Expires 8 September 2022 [Page 5]
Internet-Draft BGP Signaling for MUP March 2022
+-----------------------------------+
| QFI (1 octet) |
+-----------------------------------+
| AN TEID (4 octets) |
+-----------------------------------+
| AN Address Length (1 octet) |
+-----------------------------------+
| AN Address (variable) |
+-----------------------------------+
| UPF TEID (4 octets) |
+-----------------------------------+
| UPF Address Length (1 octet) |
+-----------------------------------+
| UPF Address (variable) |
+-----------------------------------+
The route is a combination of ST1 and ST2 routes, in that:
* The QFI, AN TEID, and AN Address information correspond to the
fields in the 3gpp-5g ST1 Route Type specific BGP-MUP NLRI:
+-----------------------------------+
| TEID (4 octets) |
+-----------------------------------+
| QFI (1 octet) |
+-----------------------------------+
| Endpoint Address Length (1 octet) |
+-----------------------------------+
| Endpoint Address (variable) |
+-----------------------------------+
* The UPF Address info corresponds to the Endpoint fields in ST2
route:
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Endpoint Length (1 octet) | <---
+-----------------------------------+
| Endpoint Address (variable) | <---
+-----------------------------------+
| Architecture specific Endpoint |
| Identifier (variable) |
+-----------------------------------+
* The UPF TEID field corresponds to the TEID in the 3gpp-5g ST2
Route Type specific BGP-MUP NLRI:
Zhang, et al. Expires 8 September 2022 [Page 6]
Internet-Draft BGP Signaling for MUP March 2022
+-----------------------------------+
| TEID (0-4 octets) |
+-----------------------------------+
4.2. Procedures
The procedures are inline with those in [I-D.mpmz-dmm-mup-safi] and
[I-D.mhkk-dmm-srv6mup-architecture].
Details will be added a future revision.
5. Security Considerations
To be provided.
6. IANA Considerations
Requests to be made for the BGP encodings in Section 4.1. Details
will be added in a future revision.
7. References
7.1. Normative References
[I-D.ietf-dmm-srv6-mobile-uplane]
Matsushima, S., Filsfils, C., Kohno, M., Garvia, P. C.,
Voyer, D., and C. E. Perkins, "Segment Routing IPv6 for
Mobile User Plane", Work in Progress, Internet-Draft,
draft-ietf-dmm-srv6-mobile-uplane-18, 18 February 2022,
<https://www.ietf.org/archive/id/draft-ietf-dmm-srv6-
mobile-uplane-18.txt>.
[I-D.mhkk-dmm-srv6mup-architecture]
Matsushima, S., Horiba, K., Khan, A., Kawakami, Y.,
Murakami, T., Patel, K., Kohno, M., Kamata, T., Garvia, P.
C., Voyer, D., Zadok, S., Meilik, I., Agrawal, A.,
Perumal, K., and J. Horn, "Segment Routing IPv6 Mobile
User Plane Architecture for Distributed Mobility
Management", Work in Progress, Internet-Draft, draft-mhkk-
dmm-srv6mup-architecture-02, 7 March 2022,
<https://www.ietf.org/archive/id/draft-mhkk-dmm-srv6mup-
architecture-02.txt>.
Zhang, et al. Expires 8 September 2022 [Page 7]
Internet-Draft BGP Signaling for MUP March 2022
[I-D.zzhang-pals-pw-for-ip-udp-payload]
Zhang, Z. and K. Patel, "PW for IP/UDP Payload without IP/
UDP Headers", Work in Progress, Internet-Draft, draft-
zzhang-pals-pw-for-ip-udp-payload-01, 4 March 2022,
<https://www.ietf.org/archive/id/draft-zzhang-pals-pw-for-
ip-udp-payload-01.txt>.
[RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
VPNs", RFC 7024, DOI 10.17487/RFC7024, October 2013,
<https://www.rfc-editor.org/info/rfc7024>.
7.2. Informative References
[I-D.ietf-bess-srv6-services]
Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R.,
Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based
Overlay Services", Work in Progress, Internet-Draft,
draft-ietf-bess-srv6-services-12, 5 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-srv6-
services-12.txt>.
[I-D.zzhang-dmm-5g-distributed-upf]
Zhang, Z., Patel, K., and T. Jiang, "5G Distributed UPFs",
Work in Progress, Internet-Draft, draft-zzhang-dmm-5g-
distributed-upf-00, 6 March 2022,
<https://www.ietf.org/archive/id/draft-zzhang-dmm-5g-
distributed-upf-00.txt>.
[RFC4363] Levi, D. and D. Harrington, "Definitions of Managed
Objects for Bridges with Traffic Classes, Multicast
Filtering, and Virtual LAN Extensions", RFC 4363,
DOI 10.17487/RFC4363, January 2006,
<https://www.rfc-editor.org/info/rfc4363>.
[_3GPP-23.501]
"System architecture for the 5G System (5GS), V17.3.0",
December 2021.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
Email: zzhang@juniper.net
Keyur Patel
Arrcus
Zhang, et al. Expires 8 September 2022 [Page 8]
Internet-Draft BGP Signaling for MUP March 2022
Email: keyur@arrcus.com
Satoru Matsushima
Softbank
Email: satoru.matsushima@g.softbank.co.jp
Zhang, et al. Expires 8 September 2022 [Page 9]
