From e23a51e4f8b9c15ea044e1e61af80bf312abf84a Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Fri, 12 Feb 2016 10:04:04 +0100 Subject: intiial check-in of GTP slides of netdevconf 1.1 --- 2016/netdevconf-gtp/netdev-gtp.html | 4357 +++++++++++++++++++++++++++++++++++ 1 file changed, 4357 insertions(+) create mode 100644 2016/netdevconf-gtp/netdev-gtp.html (limited to '2016/netdevconf-gtp/netdev-gtp.html') diff --git a/2016/netdevconf-gtp/netdev-gtp.html b/2016/netdevconf-gtp/netdev-gtp.html new file mode 100644 index 0000000..54e1de4 --- /dev/null +++ b/2016/netdevconf-gtp/netdev-gtp.html @@ -0,0 +1,4357 @@ + + + + +Osmocom kernel-level GTP implementation + + + + + + + + +
+

What is GTP / GTP in GPRS

+
+
    +
  • + +GTP, the GPRS Tunneling Protocol was first introduced with GPRS, the + packet-switched add-on to GSM networks + +
    • +
  • + +PDP contexts are sessions with an external packet data network (IP) + which provide a tunnel between the phone and that external network + +
    • +
  • + +GTP is used betwen the SGSN and GGSN to tunnel the User-plane (IP) + packet data of a PDP Context + +
    • +
  • + +latest definition in (3GPP TS 29.281 version 12.1.0 Release 12) + +
    • +
+
+
+netdev-gtp__1.png +
+
+
+
+
+

GTP in UMTS

+
+
    +
  • + +In UMTS, PDP originally remained between SGSN and GGSN + +
    • +
+
+
+netdev-gtp__2.png +
+
+
    +
  • + +With HSPA in later releases (Rel7+), user plane is moved out of SGSN + and NodeB generates GTP directly + +
    • +
  • + +hNodeB (femtocell) architecture also originates GTP directly in hNodeB + +
    • +
+
+
+netdev-gtp__3.png +
+
+
+
+
+

GTP in LTE

+
+
    +
  • + +LTE uses GTP at even more interfaces between network elements + +
    • +
  • + +LTE introduces GTP-C Version 2 for control plane, but user plane + remains GTP-U v1 like before. + +
    • +
  • + +What used to be the GGSN is now called PDN-GW in LTE + +
    • +
+
+
+netdev-gtp__4.png +
+
+
+
+
+

GTP

+
+
    +
  • + +control (GTP-C) and user (GTP-U) plane protocol + +
    • +
  • + +UDP based on well known ports (3386, 2152) + +
    • +
  • + +per PDP context/tunnel identifiers (TID) + +
      +
    • + +one for each direction(!) in GTP v1 + +
      • +
    • + +is the only identifier for tunnel, not IP/Port tuples! + +
      • +
    +
    • +
  • + +support for packet sequnce numbers and reordering + +
    • +
+
+
+
+

GTP-C

+
+

control protocol for:

+
    +
  • + +exchanging meta data + +
    • +
  • + +assigning parameters to client: + +
      +
    • + +IPv4 addresses + +
      • +
    • + +IPv6 prefixes + +
      • +
    • + +DNS servers + +
      • +
    • + +… + +
      • +
    +
    • +
  • + +establishing and removing tunnels + +
    • +
  • + +moving tunnel endpoints to other SGW’s + +
    • +
+
+
+
+

GTP-U

+
+

two main jobs:

+
    +
  • + +per client tunnelling of IP packets + +
    • +
  • + +path maintenance + +
      +
    • + +echo requests/replies + +
      • +
    • + +error reporting + +
      • +
    +
    • +
+
+
+netdev-gtp__5.png +
+
+
+
+
+

Problems with Userspace GTP

+
+
    +
  • + +Userspace GTP was fine with GPRS speeds + +
      +
    • + +Packet rates / bandwidths small compared to routing + +
      • +
    +
    • +
  • + +With HSPA and particularly LTE, the world has changed + +
      +
    • + +Signalling / Control Plane traffic is very limited + +
      • +
    • + +User Plane traffic is very high bandwidth + +
      • +
    +
    • +
+
+
+
+

Osmocom kernel-level GTP

+
+
    +
  • + +Move bandwidth-critical User Plane into Linux kernel + +
    • +
  • + +Keep Control Plane stays in Userspace (OpenGGSN) + +
    • +
  • + +Use netlink based API to control user plane in kernel + +
    • +
  • + +Started by Harald Welte + Pablo Neira @ sysmocom in 2012 + +
      +
    • + +unfortunately abandoned due to customer disappearing + +
      • +
    +
    • +
  • + +picked up by Andreas Schultz @ travelping in 2015 + +
      +
    • + +fixed Harald + Pablo’s bugs + +
      • +
    • + +introduce network namespace support + +
      • +
    +
    • +
+
+
+
+

Design

+
+
    +
  • + +netlink API built on top of genl + +
    • +
  • + +initialization: + +
      +
    • + +create GTP socket in userspace + +
      • +
    • + +create tun like network interface + +
      • +
    • + +bind GTP sockets to it + +
      • +
    +
    • +
  • + +for each PDP context, user space adds one record + +
      +
    • + +IP address assigned to MS for this PDP context + +
      • +
    • + +TEIDs to identify mobile-originated packets + +
      • +
    • + +SGSN IP for GTP header of mobile-terminated packets + +
      • +
    +
    • +
+
+
+
+

Design

+
+
    +
  • + +netlink API built on top of genl + +
    • +
  • + +all PDP contexts share one tun device + +
      +
    • + +one tun device for all subscribers, not one per subscriber + +
      • +
    +
    • +
+
+
+netdev-gtp__6.png +
+
+
+
+
+

STATUS

+
+
    +
  • + +working + +
      +
    • + +GTP-U v0 and v1 for IPv4 over IPv4 + +
      • +
    • + +multiple tunnels supported + +
      • +
    • + +only single APN (multiple IP ranges not permited) + +
      • +
    +
    • +
  • + +Limitations + +
      +
    • + +no IPv6 support + +
      • +
    • + +no offload support + +
      • +
    +
    • +
  • + +existing users (both GPLv2) + + +
    • +
+
+
+
+

TODO

+
+
    +
  • + +TODO: + +
      +
    • + +final round of clean-up, submission for mainline + +
      • +
    • + +fix or remove IPv6 support + +
      • +
    +
    • +
  • + +discussion items: + +
      +
    • + +path MTU discovery + +
      • +
    • + +implications by/for offloading faetures (csum / gso / …) + +
      • +
    +
    • +
  • + +wishlist + +
      +
    • + +light-weight tunneling integration + +
      • +
    +
    • +
+
+
+
+

The End

+
+

Questions?

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+
+ + -- cgit v1.2.3