RFC 3583

Requirements of a Quality of Service (QoS) Solution for Mobile IP

📅 published September 2003, from ietf

RFC 3583: Requirements of a Quality of Service (QoS) Solution for Mobile IP 🎀

  • Written by H. Chaskar, Ed., from Nokia Research Center 💼
  • Category: Informational 📚
  • Date: September 2003 🗓️
  • Obsoletes or updates: the title block doesn't list anything it obsoletes or updates 🙅‍♀️

Status of this Memo ✨

Okay so this memo is just info for the Internet community, bestie. It does NOT specify an Internet standard of any kind 🙅‍♀️ Distribution is unlimited, so share it with everyone 💅

Copyright (C) The Internet Society (2003). All Rights Reserved. 💜

Abstract 🌸

Mobile IP makes sure packets get routed correctly to a mobile node even when it switches up its point of attachment to the Internet 🦋 But it also needs proper Quality of Service (QoS) forwarding treatment for the mobile node's packet stream at the intermediate nodes in the network, so QoS-sensitive IP services can work over Mobile IP 🔥 This document lays out the requirements for an IP QoS mechanism that works well with Mobile IP ✨

Table of Contents 🧚

1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.1.  Problem Statement. . . . . . . . . . . . . . . . . . . .  2
    1.2.  An approach for solving QoS problem in Mobile IP . . . .  3
2.  Terminology. . . . . . . . . . . . . . . . . . . . . . . . . .  3
3.  Requirements of a QoS solution for Mobile IP . . . . . . . . .  3
    3.1.  Performance requirements . . . . . . . . . . . . . . . .  4
    3.2.  Interoperability requirements. . . . . . . . . . . . . .  5
    3.3.  Miscellaneous requirements . . . . . . . . . . . . . . .  6
    3.4.  Standard requirements. . . . . . . . . . . . . . . . . .  7
4.  Security Considerations. . . . . . . . . . . . . . . . . . . .  7
5.  Recommendation . . . . . . . . . . . . . . . . . . . . . . . .  8
6.  Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . .  8
7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
    7.1.  Normative References . . . . . . . . . . . . . . . . . .  8
    7.2.  Informative References . . . . . . . . . . . . . . . . .  8
8.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  9
9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 10

1. Introduction 🦋

Okay so Mobile IP is the tech that lets a "mobile node" (MN) switch up its point of attachment to the Internet while it's still chatting with the "correspondent node" (CN) using IP 💬 The formal description lives in [1, 6]. Mobile IP mainly cares about making sure packets still reach the MN's current point of attachment, which is the whole main character moment 👑

It's also essential to give proper Quality of Service (QoS) forwarding treatment to packets sent by or headed to the MN 💅 As they travel different routes through the network because the node is moving, they need to keep their QoS. This document is going to figure out exactly what requirements Mobile IP puts on an IP QoS mechanism 🔥

1.1. Problem Statement 😭

When an MN using Mobile IP does a handover from one access router to another, the path its packet stream takes through the network might change 🛣️ That change could be a small segment near the end of the path, or it could affect the whole end-to-end path 🌍 Also, the packets from the MN's ongoing session may start using a new care-of address after the handover. So some forwarding functions in the nodes might not recognize them, even along the part of the end-to-end path that didn't change 🙈 And finally, the handover might happen between subnets under different administrative control 💀

Given all that, it's essential to set up proper QoS support for the MN's packet stream along the new packet path 💖

1.2. An approach for solving the QoS problem in Mobile IP 🧠

There are four important steps to solving the QoS problem for Mobile IP, and they go like this 📋

  1. List the requirements that Mobile IP places on the QoS mechanism.
  2. Evaluate current IP QoS solutions against these requirements.
  3. Decide if current solutions need to be extended, or if new ones need to be defined.
  4. Depending on the result of step 3, define new solutions or fix the old ones.

This document only handles the first step, the requirements step 🎯 Steps 2, 3, and 4 aren't covered in detail here. Still, to give you useful insight into the Mobile IP QoS problem, the document sometimes points out where some well-known current proposals for QoS support for the packet stream in the network fall short when they're used directly with Mobile IP 👀

2. Terminology 📖

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [2]. 🫶

3. Requirements of a QoS solution for Mobile IP 💜

This section describes the requirements for a QoS solution that works well with Mobile IP ✨ Just so you know, only the Mobile IP-specific requirements are in here. We don't assume any particular version (4 or 6) of IP, so solutions can be designed for IPv4 and IPv6 separately, or one solution can work for both versions 🌈

In this document, we assume that the target access router for the MN's handover is already decided by other protocols 🧚 For example, the Seamoby working group has started work on candidate access router discovery protocols [7]. So any QoS-capability-specific negotiations that might affect the handover decision are outside the scope of the QoS solution itself. They need to be handled by the candidate and target access router selection protocols instead 💅

3.1. Performance requirements 🔥

1. Minimize the interruption in QoS at the time of handover: 😭

At handover, QoS would get interrupted if packets sent by or headed to the MN reach an intermediate node on the new packet path without that node knowing their QoS forwarding requirement. Those packets would then get default forwarding treatment, which is giving major downgrade energy 💀 That QoS interruption MUST be minimized. A good metric for this is the number of packets that might end up served with the "default" QoS at handover time. That number of packets MUST be minimized 📉

As an example, this performance metric is computed in [8] for end-to-end RSVP signaling [3] with Mobile IPv6. It shows that when the end-to-end path of packets changes a lot after handover, or when the care-of address changes after handover, the OPWA (One Pass With Advertisement) reservation model used by RSVP causes a latency of about one round-trip time between the MN and the CN before QoS can be set up on the new packet path ⏳ So packets using the new care-of address that get released by the MN or the CN during that round-trip time, after these nodes are ready to use the new care-of address, might get default forwarding treatment at the intermediate nodes 🙃 That kind of delay in QoS programming might be fine when a session is starting up, but it's NOT acceptable in the middle of an active session, like with handover 🙅‍♀️

2. Localize the QoS (re)establishment to the affected parts of the packet path in the network: 🗺️

Plenty of times, handover only changes a small segment of the end-to-end path of the MN's packet stream near the end. In that case, the QoS mechanism MUST limit the extent of QoS (re)establishment to just the affected segment of the end-to-end path 🎯

But heads up, handover can sometimes change the end-to-end path of the MN's packet stream a lot. That can happen, for example, when handing over between different administrative domains 🌍 If the QoS mechanism used to set up QoS support for the MN's packet stream along the new packet path is based on explicit end-to-end provisioning, then it MUST do that provisioning at the time of such a handover 🧾

When the care-of address changes upon handover, some signaling might be needed even over the unchanged part of the end-to-end path. This is true if that path has any QoS mechanisms that use the IP address as a key to forwarding functions. Examples are FILTER SPECs in the IntServ nodes or packet classifiers at the edges of DiffServ networks 🔑 Even so, double provisioning of resources over the unchanged part of the packet path MUST be avoided 🚫

Also, the QoS signaling protocol such as RSVP [9] can localize QoS signaling to the affected parts of the end-to-end path if the care-of address does NOT change upon handover ✨ But if the care-of address does change, RSVP as currently defined [4] fails to localize the QoS signaling 😤 On top of that, it causes double reservations on the part of the end-to-end path that stays the same after handover 💀

3. Releasing after handover the QoS state (if any) along the old packet path: 🧹

The QoS mechanism MUST provide some way (explicit or timer-based) to release any QoS state along the old packet path that isn't needed after handover 🗑️ It's desirable that the unwarranted QoS states, if there are any along the old path, get released as quickly as possible at handover time ⚡ Keep in mind that during handover, the MN might not always get a chance to send an explicit tear-down message along the old path, because link layer connectivity with the old access router can get lost 📡

3.2. Interoperability requirements 🫶

  1. Interoperability with mobility protocols: okay so there are a bunch of mobility protocols that are basically Mobile IP's bestie 💖 Some are already defined and some might get defined in the IETF later, mostly over in the Mobile IP and Seamoby working groups. Examples are fast handover [10, 11], localized mobility management [12, 13], context transfer [5] etc. The QoS mechanism for Mobile IP SHOULD take advantage of these mobility protocols so it can run in optimized mode ✨ BUT the QoS scheme MUST have provisions to get its job done even if one or more of these mobility protocols aren't being used. no cap, it has to be able to hold its own solo too 💪
  2. Interoperability with heterogeneous packet paths as regards QoS paradigms: the new path after a handover, for the MN's packet stream, might run through network domains that use different QoS paradigms than the old path did 🦋 The QoS mechanism for Mobile IP SHOULD be able to set up proper QoS forwarding treatment for the MN's packet stream along packet paths that use different QoS paradigms (best current practices), in a way that matches the QoS mechanism running along those paths.

Here's an example to make it click 🧚 Say the MN is attached to an access router that's the edge router of a DiffServ network, and the packet classifier and traffic policer for the MN's flows are currently set up in that access router. Now the MN needs to hand over to the access router sitting at the edge of an IntServ network. That new access network would expect an exchange of RSVP messages so proper QoS forwarding treatment can get set up for the MN's packet stream in there. The QoS mechanism for Mobile IP SHOULD have provisions to handle that kind of heterogeneity, where the QoS mechanisms along different packet paths aren't the same 😭🫶

3.3. Miscellaneous requirements 🎀

  1. QoS support along multiple packet paths: after the MN hands over from one access router to another, there could be multiple paths its packets might travel 🌈 Examples of these paths are: the route-optimized path between the MN and its CN, the triangle route via Home Agent (HA), a temporary tunnel between old and new access routers, a reverse tunnel from the new access router (Foreign Agent) to HA etc. A QoS mechanism SHOULD be able to support QoS along the different potential packet paths. However, whether all paths get supported or only a subset of them will be decided by external mechanisms such as mobility management, policy, location privacy requirements and so on. Also, the same QoS mechanism might not be able to support all of these paths, so it's not one-size-fits-all 🙈
  2. Interactions with wireless link-layer support for QoS: a huge number of Mobile IP devices are going to be connected to the Internet over wireless links 📶 so the QoS mechanism for Mobile IP MAY provide some information to the wireless link layers so they can support the QoS that's needed 🍓

Here's a scenario that would totally benefit from that 👑 Imagine two UDP streams carrying the same media, but they need different levels of error protection at the wireless link layer because of how their encoding schemes work. The packets in these two streams are equally delay sensitive (so playout stays synced at the receiver), so the IP layer might treat them the same way when it comes to queuing. But they might need to be sent over wireless channels with different error characteristics (say, different FEC coding or power levels) 🥹

The QoS information shared for the wireless link layers SHOULD be meaningful both ways 💅 It should work for applications that live on top of IP, so they can choose an IP service with certain QoS characteristics, and for wireless link QoS managers, so they can map that info to the details of lower layer mechanisms and their parameters.

In the scenario above, that QoS information could be expressed as the acceptable loss rate of IP packets in the UDP stream. This parameter lets the UDP application pick the IP service whose QoS matches what it needs, and it also lets the wireless link QoS managers pick the right wireless channel to send that UDP stream's packets over ✨

3.4. Standard requirements 💜

The QoS solution for Mobile IP SHOULD satisfy standard requirements like scalability, security, conservation of wireless bandwidth, low processing overhead on mobile terminals, providing hooks for authorization and accounting, and robustness against failures of any Mobile IP-specific QoS components in the network. It's not possible to set quantitative targets for these desirable properties 🥲 but the QoS solution MUST be evaluated against these criteria. Non-negotiable bestie ✋

4. Security Considerations 🔐

Okay, this section is SERIOUS, so read it carefully 🚨

The QoS (re)establishment triggered by node mobility MUST be guarded against security attacks. These attacks could be launched by malicious nodes that spoof the QoS signaling to make it look to the intermediate nodes like the MN has undergone a handover. That could wreck the QoS offered to the MN's ongoing sessions, because the intermediate nodes might then tear down the QoS along some segments of the true packet paths between MN and CN. The malicious nodes could also request a reduced level of QoS or supply fake packet classifiers, which would mess with QoS over some segments (for example, ones that didn't get affected by the spoofed handover) of the true packet paths between MN and CN. On top of that, network resources could get wasted or used in unauthorized ways by malicious nodes that spoof the MN's handover. To prevent this, the QoS mechanism MUST provide means for intermediate nodes to verify the authenticity of handover-induced QoS (re)establishment 🛡️💀

5. Recommendation 🎯

In this document, we described the requirements for a QoS solution so Mobile IP can work well with it 🌸 The expectation is that the appropriate working group will use this requirements document to build a QoS solution for Mobile IP 🧚

6. Acknowledgment 🫶

I want to shout out the participants on the mailing list that was set up to discuss the requirements above 💖 Their contributions and active participation in those discussions were super useful in putting this document together. Special thanks, in alphabetical order, to Brian Carpenter (IBM), Marc Greis (Nokia), Glenn Morrow (Nortel), Phil Roberts (Megisto) and Michael Thomas (Cisco) for their input while this document was being prepared 👑

7. References 📚

7.1. Normative References

  • [1] Perkins, C., Ed., "IP mobility support for IPv4", RFC 3344, August 2002.
  • [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
  • [3] Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L., Speer, M., Braden, R., Davie, B., Wroclawski, J. and E. Felstaine, "A Framework for Integrated Services Operation over Diffserv Networks", RFC 2998, November 2000.
  • [4] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997.
  • [5] Kempf, J., Ed., "Problem description: Reasons for performing context transfers between nodes in an IP Access Network", RFC 3374, September 2002.

7.2. Informative References

  • [6] Johnson, D., Perkins, C. and J. Arkko, "Mobility support in IPv6", Work in Progress, May 2003.
  • [7] Trossen, D., et al., "Issues in Candidate Access Router discovery for seamless IP handoffs", Work in Progress, October 2002.
  • [8] Chaskar, H. and R. Koodli, "QoS support in Mobile IP version 6", IEEE Broadband Wireless Summit (Networld+Interop), May 2001.
  • [9] Thomas, M., "Analysis of Mobile IP and RSVP interactions", Work in Progress, February 2001.
  • [10] MIPv4 Handoffs Design Team, "Low latency handoffs in Mobile IPv4", Work in Progress, June 2002.
  • [11] Koodli, R., Ed., "Fast handovers for Mobile IPv6", Work in Progress, March 2003.
  • [12] Williams, C., Ed., "Localized mobility management requirements", Work in Progress, March 2003.
  • [13] Soliman, H., et al., "Hierarchical MIPv6 mobility management (HMIPv6)", Work in Progress, October 2002.

8. Authors' Addresses 📮

The working group can be contacted via the current chair:

John Loughney
Nokia Research Center
11-13 Italahdenkatu
00180 Helsinki
Finland

EMail: john.loughney@nokia.com

Questions about this memo can be directed to the editor:

Hemant Chaskar
Nokia Research Center
5 Wayside Road
Burlington, MA 01803, USA

Phone: +1 781-993-3785
EMail: hemant.chaskar@nokia.com

Copyright (C) The Internet Society (2003). All Rights Reserved. 💖

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