Re: [netext] Review of ID: draft-ietf-netext-pmipv6-sipto-option-01.txt
<pierrick.seite@orange.com> Wed, 01 February 2012 12:09 UTC
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Date: Wed, 01 Feb 2012 13:09:32 +0100
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Thread-Topic: [netext] Review of ID: draft-ietf-netext-pmipv6-sipto-option-01.txt
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From: pierrick.seite@orange.com
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Subject: Re: [netext] Review of ID: draft-ietf-netext-pmipv6-sipto-option-01.txt
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Hi, Please find below my review of draft-gundavelli-netext-pmipv6-sipto-option-01: This document is in good shape and my comments are mainly editorial. My main concern is that the introduction is focusing too much on the 3GPP S2a use-case while the offload option could be useful in other type of architectures. With the current text, the reader may think that the offload option has been designed only for 3GPP/EPC. So, at least the document should avoid using 3GPP specific terminology such as S2a and SIPTO. But, what about this rewording for the intro: ------ OLD TEXT ------ Mobile Operators are expanding their network coverage by integrating various access technology domains into a common IP mobile core. For providing IP mobility support to a mobile node irrespective of the access network to which it is attached, the 3GPP S2/a Proxy Mobile IPv6 [TS23402] interface, specified by the 3GPP system architecture, is providing the needed protocol glue. When this protocol interface based on Proxy Mobile IPv6 [RFC5213] is used, the mobile node is topologically anchored on the local mobility anchor [RFC5213] in the home network. The mobile node's IP traffic is always tunneled back from the mobile access gateway [RFC5213] in the access network to the local mobility anchor in the home network. ---- NEW TEXT ---- In current IP mobility architecture, the mobile node is topologically anchored on the mobility anchor in the home network. As a consequence, the mobile node's IP traffic is always tunneled back to the mobility anchor in the home network. However, some of the traffic does need mobility support and, so, does not need to be anchored. Actually, in this situation, routing can be easily optimized when using Proxy Mobile IPv6 [RFC5213]: the mobile access gateway could forward this traffic to the local Internet peering point instead of tunneling back to the local mobility anchor. The 3GPP/Wi-Fi offloading use-case is a concrete example of such an optimization. Indeed, mobile Operators are expanding their network coverage by integrating various access technology domains into a common IP mobile core. For providing IP mobility support to a mobile node irrespective of the access network to which it is attached, a Proxy Mobile IPv6 interface, specified by the 3GPP system architecture, is providing the needed protocol glue [TS23402]. Other comments on the introduction: ---- OLD TEXT ------------ some of the non-essential traffic -----NEW TEXT -------- some of the traffic Note: non-essential traffic sounds pejorative (for an conscientious operator, there is no non-essential traffic :-)) while the goal is to distinguish traffic which need mobility support from traffic which does not... accessing mobile operator services (as depicted on figure 1) is another use-case for PMIP but it is a specific usage for 3GPP/Wi-Fi interworking, so I suggest to not refer to this use-case and focus on mobility; so I've modified fig.1 (see below). 2.2 Terminology I suggest to remove SIPTO acronym which a 3GPP terminology (it gives a 3GPP coloring to the document and it should be avoided IMHO). Moreover SIPTO is not used in the rest of the document. 3. Solution Overview: ---- OLD TEXT ------------ The following illustrates the scenario where the mobile access gateway in an access network having the ability to offload some of the IPv4 traffic flows, based on the traffic selectors it received from the local mobility anchor in the home network. -----NEW TEXT -------- The following illustrates the scenario where the mobile access gateway has the ability to offload some of the IPv4 traffic flows, based on the traffic selectors it received from the local mobility anchor in the home network. ----- NEW PICTURE for figure 1 -------- _----_ _( )_ ( Internet ) (_ _) '----' | +-----------------+ (IPv4 Traffic Offload Point | Services with | at access edge gateway for | mobility support| offloaded traffic +-----------------+ Ex: HTTP Traffic Offloaded) | | | ...........................................|........... | . | +---+ . | |NAT| . | +---+ . | | _----_ | +-----+ _( )_ +-----+ [MN]----| MAG |======( IP )======| LMA |-- Internet +-----+ (_ _) +-----+ '----' ( . . . [Access Network] . [Home Network] ...................................................... 3.1 LMA considerations ------ OLD TEXT ------- The following considerations apply to the local mobility anchor and the mobile access gateway. ------- NEW TEXT --------- The following considerations apply to the local mobility anchor. Inconsistency in Figure 2: There are 6 operations in the sequence chart and 7 bullets: "7. Forwarding rule - Tunnel home/offload" is not represented in the message flow. Moreover I think the DHCP OFFER/REQUEST and ACK messages should come right after step #5. It'd lead to the following picture: MN MAG(NAT) LMA |------>| | 1. Mobile Node Attach | |------->| 2. Proxy Binding Update | |<-------| 3. Proxy Binding Acknowledgement (IPTS Option) | |========| 4. Tunnel/Route Setup | + | 5. Installing the traffic offload rules |<----->| | 6. DHCP OFFER/REQUEST/ACK exchange |------>| | 7. IPv4 packet from mobile node | + | 8. Forwarding rule - Tunnel home/offload | | | ------ OLD TEXT ------- If the received Proxy Binding Update includes the IP Traffic Offload Selector Option Section 4, but if the configuration variable, EnableIPTrafficOffloadSupport on the local mobility anchor is set to a value of (0), then the local mobility anchor MUST ignore the IP Traffic Offload Selector Option and process the rest of the packet. ------- NEW TEXT --------- If the received Proxy Binding Update includes the IP Traffic Offload Selector Option Section 4, but if the configuration variable, EnableIPTrafficOffloadSupport (Section 6) on the local mobility anchor is set to a value of (0), then the local mobility anchor MUST ignore the IP Traffic Offload Selector Option and process the rest of the packet as per [RFC5213]. ------ OLD TEXT ------- If the received Proxy Binding Update includes the IP Traffic Offload Selector Option Section 4, and if the configuration variable, EnableIPTrafficOffloadSupport on the local mobility anchor is set to a value of (1) , then the local mobility anchor can construct the traffic selectors based on the offload policy and deliver those selectors in the Proxy Binding Acknowledgement message using the IP Traffic Offload Selector Option. ------- NEW TEXT --------- If the received Proxy Binding Update includes the IP Traffic Offload Selector Option (Section 4), and if the configuration variable, EnableIPTrafficOffloadSupport (Section 6) on the local mobility anchor is set to a value of (1) , then the local mobility anchor can construct the traffic selectors based on the offload policy and deliver those selectors in the Proxy Binding Acknowledgement message using the IP Traffic Offload Selector Option. How to provision offload policy on the local mobility anchor is out of the scope of that document. What about adding the following LMA operation?: If the received Proxy Binding Update does not include the IP Traffic Offload Selector Option (Section 4), and if the configuration variable, EnableIPTrafficOffloadSupport (Section 6) on the local mobility anchor is set to a value of (1), then the local mobility anchor SHOULD not include the IP Traffic Offload Selector Option in the Proxy Binding Acknowledgement. 3.2 MAG considerations Second bullet: replace "mobility access gateway" by "mobile access gateway" --- OLD TEXT ---- The mobility access upon accepting the Proxy Binding Acknowledgement message MUST NOT enable any offload policy for that mobility session. --- NEW TEXT ---- The mobile access gateway upon accepting the Proxy Binding Acknowledgement message MUST NOT enable any offload policy for that mobility session. Is the following operation covered (Though, I'm not sure it does make sense) ? : If there is IP Traffic Offload Selector Option without selector in the corresponding Proxy Binding Acknowledgement message, the mobile access gateway SHOULD apply its policy. 4. IP Traffic Offload Selector Option For a better readability: insert carriage return after "Reserverd", "IP Traffic Offload Mode Flag", "TS Format" and "TS Selector". ---- OLD TEXT ------ If the (M) flag value is set to a value of (0), it is an indication that the identified IP flow(s) needs to be offloaded at the mobile access gateway and all other IP flows associated with that mobility session needs to be tunneled to the local mobility anchor. ---- NEW TEXT --------- If the (M) flag value is set to a value of (0), it is an indication that the identified IP flow(s) must be offloaded at the mobile access gateway and all other IP flows associated with that mobility session need to be tunneled to the local mobility anchor. ---- OLD TEXT ------ TS Format An 8-bit unsigned integer indicating the Traffic Selector Format. The value of "0" is reserved and is used when there are no selectors to carry, relevant when the option is used as a capability indicator. The value of (1) is assigned for IPv4 Binary Traffic Selector [RFC6088]. ---- NEW TEXT --------- TS Format An 8-bit unsigned integer indicating the Traffic Selector Format. The value of "0" is reserved and is used when there are no selectors to carry. In this case, the option is used only as a capability indicator. When the value of TS Format field is set to (1), the format that follows is the IPv4 Binary Traffic Selector specified in section 3.1 of [RFC6088]. ---- OLD TEXT ------ TS Selector A variable-length opaque field for including the traffic specification identified by the TS format field. When the value of TS Format field is set to (1), the format that follows is the IPv4 Binary Traffic Selector specified in section 3.1 of [RFC6088]. ---- NEW TEXT --------- TS Selector A variable-length opaque field for including the traffic specification identified by the TS format field. [the rest is already in description of TS format] 6. Protocol Configuration Variables --- OLD TEXT ---- it MUST include the IP Traffic Offload Selector option in the Proxy Binding Update messages and offload the negotiated IP flows to the access network. ---- NEW TEXT ---- it MUST include the IP Traffic Offload Selector option in the Proxy Binding Update messages and offload the negotiated IP flows to the nearest Internet peering point. 7. Security Considerations Just for discussion: Allowing the MAG to provide its policy may induce a security risk: IMU, the MAG is a more vulnerable than the LMA. For instance, if the MAG is in a residential gateway, there is a risk for that MAG to be corrupted. If so, the MAG may provide corrupted offloading policy to the LMA which has no way to check the policy. Of course this is out of scope of securing PMIP signaling but maybe we could stress the requirement for a secured policy provisioning mechanism... Hope that helps, BR, Pierrick
- Re: [netext] Review of ID: draft-ietf-netext-pmip… Sri Gundavelli
- [netext] I-D Action: draft-ietf-netext-pmipv6-sip… internet-drafts
- [netext] Review of ID: draft-ietf-netext-pmipv6-s… Ahmad Muhanna
- Re: [netext] Review of ID: draft-ietf-netext-pmip… Sri Gundavelli
- Re: [netext] Review of ID: draft-ietf-netext-pmip… Ahmad Muhanna
- Re: [netext] Review of ID: draft-ietf-netext-pmip… Sri Gundavelli
- Re: [netext] Review of ID: draft-ietf-netext-pmip… pierrick.seite