



SCHC Working Group                                             A. Mokdad
Internet-Draft                                                L. Toutain
Intended status: Standards Track                             X. Lagrange
Expires: 8 January 2026                                         A. Pelov
                                                          IMT Atlantique
                                                             7 July 2025


               Static Context Header Compression Over 5G
                      draft-mokdad-schc-into-5g-00

Abstract

   This document describes a possible integration of Static Context
   Header Compression [RFC8724] into 5G networks.

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   This Internet-Draft will expire on 8 January 2026.

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   provided without warranty as described in the Revised BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  5G Architecture . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  SCHC over 5G  . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  SCHC Placement in 5G  . . . . . . . . . . . . . . . . . .   3
     3.2.  SCHC Capability Signaling . . . . . . . . . . . . . . . .   4
     3.3.  SCHC Context Identification . . . . . . . . . . . . . . .   6
     3.4.  SCHC Packet Handling  . . . . . . . . . . . . . . . . . .   7
   4.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This document defines a solution for how Static Context Header
   Compression and fragmentation (SCHC) can be used in 5G.  It proposes
   a new architecture that integrates SCHC within the 5G core network.
   This architecture can handle both full-IP flows and SCHC flows while
   ensuring compatibility with full-IP application servers, based on
   3GPP specifications.  The document also describes the SCHC parameters
   needed to support SCHC over the 5G architecture. (to be done)

2.  5G Architecture

    +--------+                   +--------+
    |  AUSF  |-------------------|  UDM   |
    +--------+                   +--------+
       \                       /    |
        \                     /     |
         \                   /      |
            +-------------+       +-------------+
            |     AMF     |-------|     SMF     |
            +-------------+       +-------------+
            /        |                   |
           /         |                   |
          /          |                   |
   +-----+       +-----+            +-------+           +----------------+
   | UE  |-------| gNB |------------|  UPF  |-----------|  Data Network  |
   +-----+       +-----+            +-------+           +----------------+

            Figure 1: 3GPP 5G Core Architecture simplified

   The 5G network architecture is illustrated in Figure 1 . Below is a
   brief explanation of the main components

   The 5G system consists of the following main components





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   *  User Equipment (UE) It includes all devices that can connect to 5G
      networks, such as smartphones, IoT devices, etc.

   *  Radio Access Network (RAN) It consists of new radio technologies
      responsible for wireless communication between the UE and the 5G
      core network.  One of its main components is:

      gNodeB (gNB) It represents the 5G node base station.

   *  5G Core Network (5GC) It is a service-based architecture that
      comprises various network functions (NFs).  These include:

      -  AMF — Manages registration, authentication, and mobility.

      -  SMF — Handles PDU session establishment and IP address
         assignment.

      -  UPF — Routes and forwards user packets between UE and DN.

      -  UDM — Manages user identity and authorization.

      -  AUSF — Authenticates UE and manages key materials.

3.  SCHC over 5G

3.1.  SCHC Placement in 5G

  +--------+   +--------+     +--------+
  |  NSSF  |   |  AUSF  |-----|  UDM   |
  +--------+   +--------+     +--------+
       \           |           /    |
        \          |          /     |
         \         |         /      |
            +-------------+       +-------------+
            |     AMF     |-------|     SMF     |
            +-------------+       +-------------+
            /        |                   |
           /         |                   |
          /          |                   |
   +----------+    +-----+            +-------+           +----------------+
   |    UE    |----| gNB |------------|  UPF  |-----------|  Data Network  |
   | SCHC C/D |    +-----+            +-------+           +----------------+
   +----------+                           |
                                     +----------+
                                     | SCHC C/D |
                                     +----------+

        Figure 2: 5G Architecture with SCHC Integration Points



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   The proposed solution is depicted in Figure 2.  A modified User Plane
   Function (UPF), designated as SCHC-UPF and referred to as S-UPF, is
   introduced.  The UPF is a key component of the 5G core network,
   responsible for routing and forwarding user data packets between the
   User Equipment (UE) and the Data Network (DN).  The S-UPF handls SCHC
   compression and decompression processes.  It is capable of
   redirecting packets from devices that support SCHC to the SCHC
   compression/decompression (C/D) unit.

 +-----------+                                             +-----------+
 | IP/Non-IP |                                             | IP/Non-IP |
 |  (SCHC)   |                                             |  (SCHC)   |
 +-----------+          +-----------+-----------+          +-----------+
 |   SDAP    |          |   SDAP    |   GTP-U   |          |   GTP-U   |
 +-----------+          +-----------+-----------+          +-----------+
 |   PDCP    |          |   PDCP    |    UDP    |          |    UDP    |
 +-----------+          +-----------+-----------+          +-----------+
 |   RLC     |          |   RLC     |    IP     |          |    IP     |
 +-----------+          +-----------+-----------+          +-----------+
 |   MAC     |          |   MAC     |    L2     |          |    L2     |
 +-----------+          +-----------+-----------+          +-----------+
 |    L1     |          |   PHY     |    L1     |          |    L1     |
 +-----------+ <------> +-----------+-----------+ <------> +-----------+
     UE                            gNB                          UPF
              Radio Link                             N3

           Figure 3: SCHC Integration in 5G User Plane Stack

3.2.  SCHC Capability Signaling

   This subsection describes how endpoints can signal SCHC support
   during setup.

   *  During Registration procedure

















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       +-----+                       +-----+                     +-----+
       | UE  |                       | gNB |                     | AMF |
       +--+--+                       +--+--+                     +--+--+
          |                             |                           |
          |   Registration Request      |                           |
          | (5GMM Capability [SCHC])    |                           |
          |============================>|                           |
          |                             |                           |
          |                        Selects AMF                      |
          |                             |                           |
          |                             |   Registration Request    |
          |                             | (5GMM Capability [SCHC])  |
          |                             |==========================>|
          |                             |                           |
          |                             |                           |
          |                   Registration Accept                   |
          |            (5GS network feature support [SCHC])         |
          |<========================================================|
          |                             |                           |
          |                Registration Complete                    |
          |========================================================>|
          |                             |                           |

        Figure 4: SCHC Capability Signaling During 5G Registration

   *  During PDU Session establishment procedure

























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     +-----+      +-----+              +-----+            +-----+                 +------+
     | UE  |      | gNB |              | AMF |            | SMF |                 | S-UPF|
     +--+--+      +--+--+              +--+--+            +--+--+                 +--+---+
        |            |                    |                 |                        |
        |           PDU Session Establishment Request       |                        |
        |         (5GSM Core Network Capability [SCHC])     |                        |
        |==================================================>|                        |
        |            |                    |                 |                        |
        |            |                    |            Selects S-UPF and             |
        |            |                    |               IP address                 |
        |            |                    |                 |                        |
        |            |                    |                 |N4 Session Establishment|
        |            |                    |                 |         Request        |
        |            |                    |                 |----------------------->|
        |            |                    |                 |N4 Session Establishment|
        |            |                    |                 |   Response (TEID_UPF)  |
        |            |                    |                 |<-----------------------|
        |            |                    |                 |                        |
        |       PDU Session Establishment Accept            |                        |
        |    (5GSM Network feature support [SCHC])          |                        |
        |<==================================================|                        |
        |            |                    |                 |                        |
        |            |   N2 PDU Session   |                 |                        |
        |            |    Resourse setup  |                 |                        |
        |            |     response       |                 |                        |
        |            |------------------->|                 |                        |
        |            |                    |Nsmf_PDUSession_ |                        |
        |            |                    | UpdateSMContext |                        |
        |            |                    |   Request       |                        |
        |            |                    |---------------->|                        |
        |            |                    |                 | N4 Session Modification|
        |            |                    |                 |      Request           |
        |            |                    |                 |----------------------->|
        |            |                    |                 |                        |
        |            |                    |                 |                        |
        |            |                    |                 |                        |
        <-----------><------------------ Packet data flow ------------------------->

      Figure 5: SCHC Capability During PDU Session Establishment

3.3.  SCHC Context Identification

   The SCHC C/D unit stores the contexts of many devices connected to
   the network.  When a packet arrives, it must be recognized by the
   SCHC C/D in order to retrieve the appropriate device context.
   Therefore, the use of a unique identifier is essential.  Among 5G
   identifiers, there is the Permanent Equipment Identifier (PEI), which
   identifies UEs capable of accessing a 3GPP network.  What makes the



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   PEI suitable for this use is that it is known by both the 5G operator
   and the device owner, and it is transmitted to the UPF during the
   PFCP association procedure.

3.4.  SCHC Packet Handling

   This subsection presents how the S-UPF handle SCHC-compressed
   packets.











































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+-----+     +-----             +--------+                    +----+
| UE  |---->| gNB | ---------> | S-UPF  | -----------------> | DN |
+-----+     +-----+            +--------+ \                  +----+
              \                /        /\ \---------------------------------\
               \              /        /  \                                   \
       +--------------------+/        +----------------------------------------\----------------------------+
       |      IP            |         |   +---------------------+               \                           |
       | src: gNB addr      |         |   |  PFCP Session Look  |                \                          |
       | dest: UPF addr     |         |   |   Retrieve UE ID    |                 \                         |
       +--------------------+         |   +---------------------+                  \                        |
       |      UDP           |         |   +---------------------------+             \                       |
       |   Port number      |         |   | Retrieve the UE identifier|       +--------------------+        |
       +--------------------+         |   +---------------------------+       |        IP          |        |
       |      GTP           |         |               |                       +--------------------+        |
       |     TEID 2         |         |   +---------------------------+       |       UDP          |        |
       +--------------------+         |   |        SCHC D             |       +--------------------+        |
       |   SCHC Packet      |         |   |   Decompress using UE ID  |       |      Payload       |        |
       | +-------------+    |         |   |      and find context     |---->  +--------------------+        |
       | |  Rule ID    |    |         |   +---------------------------+                                     |
       | |-------------|    |         |           \           /                                             |
       | |  Residue    |    |         |            \         /                                              |
       | +-------------+    |         |      +--------------------+                                         |
       +--------------------+         |      |      IP            |                                         |
                                      |      | src: gNB addr      |                                         |
                                      |      | dest: UPF addr     |                                         |
                                      |      +--------------------+                                         |
                                      |      |      UDP           |                                         |
                                      |      |   Port number      |                                         |
                                      |      +--------------------+                                         |
                                      |      |      GTP           |                                         |
                                      |      |     TEID 2         |                                         |
                                      |      +--------------------+                                         |
                                      |      |   +-------------+  |                                         |
                                      |      |   |      IP     |  |                                         |
                                      |      |   +-------------+  |                                         |
                                      |      |   |     UDP     |  |                                         |
                                      |      |   +-------------+  |                                         |
                                      |      |   |   Payload   |  |                                         |
                                      |      |   +-------------+  |                                         |
                                      |      +--------------------+                                         |
                                      +---------------------------------------------------------------------+

             Figure 6: Uplink Data Decompression at S-UPF

4.  Normative References






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   [RFC8724]  Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
              Zuniga, "SCHC: Generic Framework for Static Context Header
              Compression and Fragmentation", RFC 8724,
              DOI 10.17487/RFC8724, April 2020,
              <https://www.rfc-editor.org/rfc/rfc8724>.

Authors' Addresses

   Amina Mokdad
   IMT Atlantique
   CS 17607, 2 rue de la Chataigneraie
   35576 Cesson-Sevigne Cedex
   France
   Email: amina.mokdad@imt-atlantique.fr


   Laurent Toutain
   IMT Atlantique
   CS 17607, 2 rue de la Chataigneraie
   35576 Cesson-Sevigne Cedex
   France
   Email: laurent.toutain@imt-atlantique.fr


   Xavier Lagrange
   IMT Atlantique
   CS 17607, 2 rue de la Chataigneraie
   35576 Cesson-Sevigne Cedex
   France
   Email: xavier.lagrange@imt-atlantique.fr


   Alexander  Pelov
   IMT Atlantique
   CS 17607, 2 rue de la Chataigneraie
   35576 Cesson-Sevigne Cedex
   France
   Email: alexander.pelov@imt-atlantique.fr













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