3gpp-analysis document and automatic tunneling

[Pekka Savola <pekkas@netcore.fi>]

Hi,

I'd like to raise one issue in the 3gpp-analysis document which bothers me 
a lot.

I'd like to either understand the reasoning for mentioning all the kinds
of automatic tunneling mechanism in this draft, or remove the references.
(the last paragraph of 2.2 quoted below, and some re-editing of the
paragraphs in 3.2.1).

In particular, I feel this is an issue about IGP/BGP tunneling.  It is
possible such methods could be used -- if the network is built just so --
but that's entirely different thing from whether they're a required or
even a recommended solution ("we have a hammer, now let's go find the
nails").

I fail to see anything 3GPP specific in the description of the network in 
3.2.1 and consequently, I'd rather not go down the rathole of describing 
how an ISP would run its network in the 3GPP scenarios/analysis document.  
Rather, I'd try to work out generic ISP scenarios in the ISP 
documents to avoid duplicating the work.

Therefore, I'd like to either understand why this is in scope and what's 
3GPP specific about it, or try to reword the text appropriately (I can 
try to help if needed).

====
 2.2 Tunneling
     
    Tunneling is a transition mechanism that requires dual IPv4/IPv6   
    stack functionality in the encapsulating and decapsulating nodes.  
    Basic tunneling alternatives are IPv6-in-IPv4 and IPv4-in-IPv6.    
    IPv6-in-IPv4 tunneling mechanisms perform as virtual IPv6 links    
    over IPv4, and they are implemented by virtual IPv6 interfaces that
	  are configured over one or more physical IPv4 interfaces. Sending
	nodes encapsulate IPv6 packets in IPv4 packets when the IPv6    
	routing table determines that the next hop toward the IPv6      
	destination address is via a tunnel interface. Receiving nodes  
	decapsulate IPv6 packets from IPv4 packets that arrive on tunnel
	interfaces. Tunneling can be static or dynamic.
        
	Static (configured) tunnels are fixed IPv6 links over IPv4. They   
    require static configuration of the IPv6 source, IPv6 next-hop and 
    IPv4 destination addresses for IPv6-in-IPv4 encapsulation. The IPv6
    destination address is specified by the application and is used to 
    determine the IPv6 next-hop address via longest-prefix-match in the
    IPv6 routing table. Configured tunnels are specified in [RFC2893].
     
    Dynamic (automatic) tunnels enable stateless encapsulation of IPv6-
	in-IPv4. They are virtual IPv6 links over IPv4 where the tunnel
	endpoints are not configured, i.e. the links are created 
    dynamically, and they only require static configuration of the IPv6
	  source address. Like in static tunneling, the IPv6 destination 
	address is specified by the application and it is used to determine
	the IPv6 next-hop address via a longest-prefix-match lookup in the 
	IPv6 routing table. But unlike static tunnels, the IPv4 destination
    address is not configured (fixed); it is derived from the IPv6     
    next-hop address in some way. For example, the IPv4 destination    
    address can be embedded in the IPv6 next-hop address. Examples of  
    dynamic tunneling mechanisms are "6to4" [RFC3056], [ISATAP], [DSTM]
    and [TEREDO].

[...]

 3.2.1 Tunneling inside the 3GPP Operator's Network

    Many GPRS operators already have IPv4 backbone networks deployed
    and they are gradually migrating them while introducing IPv6 
    islands. IPv6 backbones can be considered quite rare in the first  
    phases of the transition. If the 3GPP operator already has IPv6    
    widely deployed in its network, this subsection is not so relevant.
     
    In initial, smaller scale IPv6 deployment, where a small number of
    IPv6 in IPv4 tunnels are required to connect the IPv6 islands over
    the 3GPP operator's IPv4 network, manually configured tunnels can 
    be used. In a 3GPP network, one IPv6 island could contain the GGSN
    while another island contains the operator's IPv6 application
    servers. However, manually configured tunnels can be an 
    administrative burden when the number of islands and therefore
    tunnels rises.
  
    It is also possible to use dynamic tunneling mechanisms such as    
    "6to4" [RFC3056] and IGP/EGP routing protocol based tunneling      
    mechanisms [BGP][IGP]. Routing protocol based mechanisms such as   
    [BGP] consist of running BGP between the neighboring router tunnel 
    endpoints and using multi-protocol BGP extensions to exchange      
    reachability information of IPv6 prefixes. The routers use this    
    information to create IPv6 in IPv4 tunnel interfaces and route IPv6
    packets over the IPv4 network. It is possible to combine this with
    different types of tunnels.
[...]
    The conclusion is that in most "internal" 3GPP scenarios it is 
    preferred to use manually configured tunnels or EGP/IGP based 
    tunneling mechanisms, if it is not feasible to enable IPv6 in the  
    network infrastructure yet. 


-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings