Evdo roaming technical issues
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EVDO Roaming Technical Issues. EVDO Radius policies vs User Radius policies Can they be routed over the same links A12 vs PDSN AAA Firewalls Firewalls Firewalls Firewalls Firewalls Firewalls …. Fragmentation. Bearer Traffic Fragmentation and Packet size MTU Maximum Transmitted Unit,

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EVDO Roaming Technical Issues

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Evdo roaming technical issues

EVDO Roaming Technical Issues


Evdo roaming technical issues

  • EVDO Radius policies vs User Radius policies

    • Can they be routed over the same links

    • A12 vs PDSN AAA

  • Firewalls Firewalls Firewalls Firewalls Firewalls Firewalls …


Fragmentation

Fragmentation

  • Bearer Traffic Fragmentation and Packet size

    • MTU Maximum Transmitted Unit,

      • The Maximum Transmission Unit (MTU) is a parameter that determines the largest datagram than can be transmitted by an IP interface (without it needing to be broken down into smaller units).

    • MRU Maximum Receive Unit

      • The Maximum Receive Unit is sent to inform the peer that the implementation can receive larger packets, or to request that the peer send smaller packets.

    • Ping= 8 icmp + 20 ip + (>=40 l2tp) + (~50 ESP) = ~118byte overhead

    • If MRU is 1500 (anywhere) then max payload = ~1382

      • Before fragmentation

    • Fragmentation and Reassembly adds processing requirements


Evdo roaming technical issues

L2TP

  • Access_Reply

    • Service-Type=Framed-User

    • Tunnel-Type=L2TP

    • Tunnel-Medium-Type=IP

    • Tunnel-Server-Endpoint=x.x.x.x (public & routable)

    • Tunnel-Password=abcdefgh

    • Tunnel-Client-Auth-Id=zyxwvutsr


Evdo roaming enabled

EVDO Roaming Enabled ????


Evdo connection process

EVDO Connection Process

  • Insert PC card into laptop or turn phone on

  • Scan radio channels based on PRL for SID/NID match

  • Acquire 1x radio network with reference to EVDO channel

  • IS41 registration sent to HLR via 1x network

  • Acquire Evdo radio network

    • Waiting for connection request

  • User initiates data session (Hybrid device)

  • A12 authentication via AN-AAA

  • After valid A12, PPP user authentication sent via RNC & PDSN to AAA

  • User gets IP address

    • User connected and using EVDO

  • User moves out of EVDO coverage

  • Session forced to Dormant mode

  • Scan radio channels based on PRL for SID/NID match

  • VLR updated with service list from HLR

  • Device initiates 1X data session through PDSN

  • If VLR allows SO=33, PDSN matches IMSI and connects device to same data session.


What have we found

What have we found?

  • A customer can have Roaming Disabled in HLR and still get EVDO

  • We don’t know if this is a fault with the Registration Notification back to the handset or not.

  • You cannot stop someone from using EVDO while roaming if they have a valid PRL


What are we going to do about it

What are we going to do about it?

  • Enable/Disable roaming through PRL choice

    • Not a good option for us

  • Add field/flag in AN-AAA with a script that checks that the user is allowed to use EVDO in a roaming environment

    • Good use for Carrier-id?

  • Find out and fix the fault, if it is a fault.

    • Or is it is standards implementation issue

  • You need to know this.


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