lte: (fixes #1017) Make hardcoded EPC backhaul IP addresses configurable via attributes

Usham Royrequested to merge
ushamroy/ns-3-dev:configurable-lte-epc-ip-addresses into master

Summary

Resolves #1017 — Hardcoded IP addresses in LTE EPC backhaul links are now configurable through the ns-3 Attribute system.

Previously, the EPC helper classes used fixed IP address ranges (7.0.0.0/8, 10.0.0.0/30, 11.0.0.0/30, 12.0.0.0/30, 13.0.0.0/30, 14.0.0.0/30) for backhaul links and UE address allocation. This caused conflicts when integrating LTE with other network technologies (WiFi, IoT, multi-operator) that use overlapping address spaces.

Changes

NoBackhaulEpcHelper — 5 new attributes:

Attribute Default Purpose
X2NetworkAddress 12.0.0.0 X2 inter-eNB point-to-point links
S11NetworkAddress 13.0.0.0 S11 (MME-SGW) point-to-point links
S5NetworkAddress 14.0.0.0 S5 (SGW-PGW) point-to-point links
UeNetworkAddress 7.0.0.0 UE IP address pool base
UeNetworkMask 255.0.0.0 UE IP address pool mask

PointToPointEpcHelper — 2 new attributes:

Attribute Default Purpose
S1uNetworkAddress 10.0.0.0 S1-U (eNB-SGW data plane) links
S1apNetworkAddress 11.0.0.0 S1-AP (eNB-MME control plane) links

EmuEpcHelper — 1 new attribute:

Attribute Default Purpose
EpcNetworkAddress 10.0.0.0 All emulated EPC interfaces (S1-U, X2-U, X2-C)

Additional fixes:

  • Fixed S1uLinkEnablePcap description typo in PointToPointEpcHelper ("Enable Pcap for X2 link" -> "Enable Pcap for S1-U link")
  • Added VirtualNetDevice to PyViz netdevice_traits dictionary to prevent visualization crash
  • Wrapped Mac48Address::ConvertFrom() in try/except in PyViz core.py for devices without MAC-48 addresses

Design decisions

  • Uses Ipv4AddressValue / Ipv4MaskValue attribute types with MakeIpv4AddressAccessor / MakeIpv4MaskAccessor — consistent with existing ns-3 patterns
  • Default values match the original hardcoded values ensuring full backward compatibility
  • Member variables initialized in constructor, consumed in NotifyConstructionCompleted() after attribute system has applied user-configured values
  • All 33 caller files (11 examples + 22 tests) verified — 100% coverage

Usage example 

// Method 1: Config::SetDefault (before helper creation)
Config::SetDefault("ns3::PointToPointEpcHelper::S1uNetworkAddress",
                   Ipv4AddressValue(Ipv4Address("192.168.1.0")));

// Method 2: Command line
// ./ns3 run "lena-simple-epc --ns3::PointToPointEpcHelper::S1uNetworkAddress=192.168.1.0"

Testing

  • lte-epc-e2e-data test suite: PASSED
  • lena-simple-epc example: runs cleanly
  • Build with Python bindings and visualizer: PASSED (35/35 targets)
  • PyViz visualization: no longer crashes on LTE nodes

Closes #1017

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