~tore Tore Anderson's technology blog

IPv6 roaming in the United States

I spent some time in the United States last month. Equipped with SIM cards from both Tele2 Sweden (MCCMNC 24007) and Telenor Norway (MCCMNC 24201), I set out to test IPv6 while roaming, as I usually do while abroad.

The previous posts in this series are:

There were two mobile networks that I was able to register in and test: AT&T (3G/4G, no 2G) and T-Mobile (2G/3G/4G). The test results are found below.

I could also see three other 4G networks show up in a network scan (Caprock Cellular, Sprint and Verizon), but none of those were available to me. Presumably neither Tele2 nor Telenor have roaming arrangements with any of those operators.

AT&T - MCCMNC 310410

Home PLMN Tech IPV6 PDP context IPV4V6 PDP context
Tele2 SE 3G Fails (cause code 33) IPv4-only (cause code 50)
Tele2 SE 4G Works perfectly Works perfectly
Telenor NO 3G Fails (cause code 33) IPv4-only (cause code 50)
Telenor NO 4G Works perfectly Works perfectly

T-Mobile - MCCMNC 310260

Home PLMN Tech IPV6 PDP context IPV4V6 PDP context
Tele2 SE 2G Fails (cause code 33) IPv4-only (cause code 50)
Tele2 SE 3G Fails (cause code 33) IPv4-only (cause code 50)
Tele2 SE 4G Works perfectly Works perfectly
Telenor NO 2G Fails (cause code 33) IPv4-only (cause code 50)
Telenor NO 3G Fails (cause code 33) IPv4-only (cause code 50)
Telenor NO 4G Works perfectly Works perfectly

3GPP cause code #33 means «requested service option not subscribed», while cause code #50 means «PDP type IPv4 only allowed». The latter doesn’t indicate a fatal error, as I do automatically get a working IPv4-only connection to the Internet.

The fact that IPv6 consistently fails on 2G/3G is in all likelihood due to Tele2/Telenor’s HLR removing the IPv6 capabilities from my subscriber profile before transmitting it to AT&T/T-Mobile’s vSGSN.

Tele2 and Telenor do this to forestall the possible IPv6-related failures described in RFC 7445 sections 3 and 6. In this case, it is in all likelihood an unnecessary precaution, considering that both AT&T and T-Mobile are known to have deployed IPv6 to their own customers.