RFC 3753
Mobility Related Terminology
RFC 3753: Mobility Related Terminology 🦋
Network Working Group (the crew that writes these docs)
Authors: J. Manner, Ed. and M. Kojo, Ed. 💖
Category: Informational 🌸
Date: June 2004 🎀
Obsoletes / Updates: The title block doesn't list anything it obsoletes or updates, so this one stands on its own 🌈
Status of this Memo ✨
okay so first things first, this memo is giving information only. It's not a standard, so it doesn't specify an Internet standard of any kind 💅 And distribution is unlimited, so share it with everyone bestie 🫶
Copyright Notice 🎀
Copyright (C) The Internet Society (2004). 💜
Abstract 🔥
the vibe here is that the mobility crowd needs some shared vocab, like, badly 😭 This doc defines the terms for mobility related terminology. It came out of the Seamoby Working Group's work, but it's bigger than that. It's meant for IETF-wide chats about mobility tech and IP networks, and other working groups dealing with mobility may want to use it too ✨
Table of Contents 🧚
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 2
2. General Terms . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Mobile Access Networks and Mobile Networks. . . . . . . . . . 10
4. Handover Terminology. . . . . . . . . . . . . . . . . . . . . 15
4.1. Scope of Handover . . . . . . . . . . . . . . . . . . . 16
4.2. Handover Control. . . . . . . . . . . . . . . . . . . . 17
4.3. Simultaneous connectivity to Access Routers . . . . . . 19
4.4. Performance and Functional Aspects. . . . . . . . . . . 19
4.5. Micro Diversity, Macro Diversity, and IP Diversity. . . 21
4.6. Paging, and Mobile Node States and Modes. . . . . . . . 22
4.7. Context Transfer. . . . . . . . . . . . . . . . . . . . 24
4.8. Candidate Access Router Discovery . . . . . . . . . . . 24
4.9. Types of Mobility . . . . . . . . . . . . . . . . . . . 25
5. Specific Terminology for Mobile Ad-Hoc Networking . . . . . . 26
6. Security-related Terminology. . . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. Contributors. . . . . . . . . . . . . . . . . . . . . . . . . 28
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
10. Informative References. . . . . . . . . . . . . . . . . . . . 29
11. Appendix A - Index of Terms . . . . . . . . . . . . . . . . . 31
12. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 35
13. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 361. Introduction 💖
okay so this doc lays out the terminology for Seamoby folks to use in their docs and chats. Other mobility groups can borrow it too, so everyone in IP mobility is speaking the same language 🗣️✨
some of the terms aren't really IP-specific, but they're in here to make everything match up. Like, 'Access Point' and 'base station' are the same thing from the IP point of view, but 'Access Router' is a totally different beast 👑 The authors also hope this can cover mobile ad-hoc networks 🌸
Important bit: this isn't inventing new vocab. The authors actually want feedback on sharper definitions and on terms that are missing or not needed 🫶 It's a team project with people from lots of engineering backgrounds, so it's already a step toward harmonizing things 💅
the terms are sorted into groups. First up are general terms and mobile access networks, then handover terms, and last are the ones used by the MANET and NEMO working groups 🦋
2. General Terms 🌈
Bandwidth
the total width of the frequency band that a communications channel has available or uses. It's usually measured in Hertz (Hz). A channel's bandwidth limits how much channel capacity it can have 💜
Bandwidth utilization
the actual rate of information transfer over a link, shown as a percentage of the link's theoretical maximum channel capacity, based on Shannon's Law 🔥
Beacon
a control message that a node (especially a base station) broadcasts so all the other nodes nearby know it's still around. It can also carry extra status or configuration info 📡✨
Binding Update (BU)
a message saying what a mobile node's current mobility binding is, especially its care-of address 🎀
Care-of-Address (CoA)
an IP address linked to a mobile node while it's visiting a foreign link. The subnet prefix of this address is a foreign subnet prefix 🌸 When a packet is sent to the mobile node and shows up at its home network while the node is away and has registered a Care-of Address, the Home Agent in the home network forwards it to that address 🦋
Channel
a slice of the physical medium that lets several uses share the medium independently. Channels can come from splitting the medium into time slots, spectral bands, or decorrelated coding sequences 🧚
Channel access protocol
a protocol that handles access to the channels in the physical communications medium and can also decide who gets which channel. Nodes using it only communicate once they have uncontested access to a channel, so there's no interference 💅
Channel capacity
the total amount of information (usually bits) a link can carry per unit time. With a given bandwidth, the theoretical maximum channel capacity comes from Shannon's Law. A channel's actual capacity depends on its bandwidth, the coding system, and the signal to noise ratio 💖
Control message
info passed between two or more network nodes to keep protocol state up to date. It doesn't have to be tied to any specific application ✨
Distance vector
a trait of some routing protocols. Each node keeps, for every destination it wants, the distance to that destination and a vector (the next hop) pointing toward it 🗺️
Fairness
a property of channel access protocols where the medium is shared fairly among all the eligible nodes on the link. Fairness doesn't always mean equality, especially when some nodes get access based on unequal priority or classification 👑
Flooding
the process of delivering data or control messages to every node in the network being looked at 🌊
Foreign subnet prefix
a bit string made of some number of starting bits of an IP address. It identifies a node's foreign link within the Internet topology 🌍
Forwarding node
a node that forwards datagrams from one of its neighbors on to another 🔁
Home Address (HoA)
an IP address given to a mobile node as its permanent address. It sits within the mobile node's home link. Standard IP routing will deliver packets sent to a mobile node's home address to its home link [9] 🏠
Home Agent (HA)
a router on a mobile node's home link that the mobile node has registered its current care-of address with. While the mobile node is away from home, the home agent catches packets on the home link headed for the mobile node's home address, encapsulates them, and tunnels them to the registered care-of address 🛰️✨
Home subnet prefix
a bit string made of some number of starting bits of an IP address. It identifies a node's home link within the Internet topology. This is the IP subnet prefix that matches the mobile node's home address, as defined in [9] 🏡
Interface
a node's point of attachment to a link 🔌
IP access address
an IP address (often handed out dynamically) that a node uses to show where it's currently attached to the local network. It's usually different from the mobile node's home address. While visiting a foreign network, the IP access address may not be suitable as an endpoint address for anything except very short-lived applications. So the IP access address is usually used as the node's care-of address instead 💜
Link
a communication facility or physical medium that can carry data between multiple network nodes, like an Ethernet (simple or bridged). A link is the layer right below IP. In the layered stack model, the Link Layer (Layer 2) sits below the Network (IP) Layer (Layer 3) and above the Physical Layer (Layer 1) 🧱
Asymmetric link
a link whose transmission characteristics differ depending on the relative position or design of the transmitter and receiver on that link. For example, one transmitter might have a much longer range than another transmitter on the same medium 📶
Link establishment
the process of setting up a link between the mobile node and the local network. It can mean allocating a channel or other local wireless resources, and possibly a minimum level of service or bandwidth 🎀
Link-layer trigger (L2 Trigger)
info from the link layer that tells the network layer about the detailed events in handover sequencing at the link layer. L2 triggers aren't tied to any one link layer. They're generalizations of link layer info from a wide range of link layer protocols [4] ⚡
Link state
a trait of some routing protocols where every node in the network is expected to keep info about every link in the network topology 🗺️
Link-level acknowledgment
a protocol strategy, usually used over wireless media, that requires neighbors to acknowledge receiving packets (usually unicast only) from the transmitter. These strategies aim to avoid packet loss or delay caused by a lack of, or unwanted traits in, higher level protocols. Link-layer acknowledgments are often part of Automatic Repeat-Request (ARQ) algorithms that boost link reliability 🔁💖
Local broadcast
the delivery of data to every node within range of the transmitter 📣
Loop-free
a property of routing protocols where the path a data packet takes from source to destination never goes through the same intermediate node twice before it arrives 🌀
Medium Access Protocol (MAC)
a protocol that handles access to, and possibly allocation of, the physical communications medium. Nodes using it can only communicate once they have uncontested access to the medium, so there's no interference. When the physical medium is a radio channel, the MAC is the same as the Channel Access Protocol 📻✨
Mobile network prefix 🌸
(to be continued in part 2!) 🫶
A bit string made up of some number of initial bits of an IP address, which identifies the entire mobile network within the Internet topology. Every node in a mobile network necessarily has an address containing this prefix. 🏠✨
Mobility factor 🦋
The relative frequency of node movement, compared to the frequency of application initiation. Basically, how often nodes are on the move versus how often apps start stuff. 🏃♀️💨
Multipoint relay (MPR) 💅
A node that gets picked by its one-hop neighbor to re-transmit all broadcast messages it receives. The message must be new, and the time-to-live field of the message must be greater than one. Multipoint relaying is a technique for cutting down on redundant re-transmissions while a broadcast message spreads through the network. It's giving efficiency, bestie! 🌸
Neighbor 🫶
A "neighbor" is any other node that data can be propagated to directly over the communications medium, without needing any other forwarding node to help. No middleman, just vibes. 💖
Neighborhood 🌈
All the nodes that can receive data on the same link from one node whenever that node transmits data. ✨
Next hop 🧚
A neighbor that has been selected to forward packets along the way to a particular destination. ⭐
Payload 🎀
The actual data within a packet, not including network protocol headers that weren't inserted by an application. Okay, this one's important: payloads are different between layers! Application data is the payload of TCP, which is the payload of IP, which in turn is the payload of link layer protocols, and so on. So you always have to say which layer you're talking about when you say "payload," or you'll be totally lost, no cap. 😭
Prefix 🌙
A bit string made up of some number of initial bits of an address. 🎀
Routing table 🗺️
The table where forwarding nodes keep information (including the next hop) for various destinations. It's the group chat of where-to-send-stuff. 💜
Route entry 🍓
An entry for a specific destination (unicast or multicast) in the routing table. ✨
Route establishment 🔍
The process of determining a route between a source and a destination. Figuring out the path, bestie! 🛤️
Route activation 🚀
The process of putting a route into use after it has been determined. Route established? Cool. Now let's actually USE it. 💅
Routing proxy 🫧
A node that routes packets by overlays, for example by tunneling, between communicating partners. The Home Agent and Foreign Agent are examples of routing proxies, because they receive packets destined for the mobile node and tunnel them to the mobile node's current address. Main character energy for these two! 👑
Shannon's Law 🌟
A statement defining the theoretical maximum rate at which error-free digits can be transmitted over a bandwidth-limited channel in the presence of noise. No practical error correction coding system exists that can closely approach the theoretical performance limit given by Shannon's law. Honestly? Iconic, but also a little humbling. 🥲
Signal strength 📡
The detectable power of the signal carrying the data bits, as seen by the receiver of the signal. ⚡
Source route 🧭
A source route from node A to node B is an ordered list of IP addresses, starting with the IP address of node A and ending with the IP address of node B. Between A and B, the source route includes an ordered list of intermediate hops, as well as the interface index of the interface through which the packet should be transmitted to reach the next hop. The list of intermediate hops might not include all visited nodes, since some hops might be omitted for one reason or another. 🗺️💖
Spatial re-use 🌺
Simultaneous use of channels with identical or close physical characteristics, but located spatially far enough apart to avoid interference (i.e., co-channel interference). Same channel, different location, zero drama. 🦋
System-wide broadcast 📢
Same as flooding, but used in contrast to local broadcast. 🌊
Subnet 🏘️
A subnet is a logical group of connected network nodes. In IP networks, nodes in a subnet share a common network mask (in IPV4) or a network prefix (in IPv6). It's the friend group that shares the same address vibe. 🫶
Topology (Network Topology) 🕸️
The interconnection structure of a network: which nodes are directly connected to each other, and through which links they are connected. Some simple topologies have been given names, such as 'bus topology', 'mesh topology', 'ring topology', 'star topology' and 'tree topology'. Each one has its own aesthetic, periodt. 💅✨
Triggered update ⚡
A solicited route update transmitted by a router along a path to a destination. 🍓
3. Mobile Access Networks and Mobile Networks ✨
okay so to support host mobility, a set of nodes out at the network edge may need some special functions 🦋 That set of nodes forms a mobile access network, and it may or may not be part of the global Internet. Figure 1 shows two examples of these access network topologies. The figure is a reference architecture, basically an IP network with the components we're defining in this section 🗺️
We want to define the Access Network (AN) concept, which may also support enhanced mobility 💜 Here's the tea: to handle routing and QoS for mobile nodes, existing routing protocols (like Open Shortest Path First (OSPF) [14]) may not be a good fit for keeping forwarding information for these nodes, since they keep changing where they attach to the Access Network 😭 So these new functions get built into routers with extra capabilities.
There are three types of Access Network components. First, Access Routers (AR) handle the last hop to the mobile, usually over a wireless link 📶 Second, Access Network Gateways (ANG) sit on the boundary toward the fixed network and shield the fixed network from the specialized routing protocols 🛡️ Third, there are (optionally) other internal Access Network Routers, which might be needed in some cases to support the functions 🧚 The Access Network is made up of the equipment needed to support this specialized routing, so that's AR or ANG. And yes, AR and ANG may be the same physical nodes 🫶
We also need some basic terms for mobile networks: mobile network, mobile router (MR), and mobile network node (MNN) 🎀 If you want more terminology, check [13]. For a deeper dive, the working group documents of the NEMO Working Group are the place to go 📚
Note: this reference architecture is not well suited for people dealing with Mobile Ad-hoc Networks (MANET). Sorry MANET people, it's not you, it's the architecture 💀
|
|
--- ------ ------- |
--- | <--> | | -------| AR | -------------------| | |
| |--[] --- /------ \ /| ANG |--|
--- AP / \ / | | |
MH / \ / ------- |
(with wireless ___ / ------- |
device) | |---- | ANR | |
--- ------- |
AP / \ |
/ \ ------- |
--- ------ / \| | |
| |-------| AR |---------------------| ANG |--|
--- ------ | | |
AP ------- |
|
Access Network (AN) 1 |
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -|
Access Network (AN) 2 |
|
|
--- ------ ------- |
--- | <--> | | -------| AR | -------------------| | |
| |--[] --- /------ /| ANG |--|
--- AP / / | | |
MH / / ------- |
(with wireless ___ / / |
device) | |---- / |
--- / |
AP / |
/ |
| --- ------ ------- |
--- | | <->| |-------| AR |---------| ANR | |
| |-| [] --- \ ------ ------- |
--- | -----| AP \ / |
MNN |--i MR e \ / |
| ------ --- \ ------ / |
--- | (with | |-------| AR |------- |
| |-| wireless --- ------ |
--- | device) AP |
MNN 'i': MR ingress interface |
'e': MR egress interface |
|
Figure 1: Reference Network ArchitectureNow the definitions, which are the fun part, I promise 💅
Mobile Node (MN)
An IP node that's able to change its point of attachment to the network. A Mobile Node can be either a Mobile Host (no forwarding functionality) or a Mobile Router (forwarding functionality) 🦋
Mobile Host (MH)
A mobile node that's an end host and not a router. A Mobile Host can send and receive packets, meaning it can be a source or destination of traffic, but it doesn't forward traffic for anyone else 🌸
Fixed Node (FN)
A node, either a host or a router, that can't change its point of attachment to the network or its IP address without breaking open sessions. Stay put, bestie 🧚
Mobile network
An entire network that moves as a unit and dynamically changes its point of attachment to the Internet, which means its reachability in the topology changes too 🚌 The mobile network is made up of one or more IP-subnets and is connected to the global Internet through one or more Mobile Routers (MR). The internal configuration of the mobile network is assumed to be relatively stable with respect to the MR.
Mobile Router (MR)
A router that can change its point of attachment to the network by moving from one link to another link 🏎️ The MR can forward packets between two or more interfaces, and it may also run a dynamic routing protocol that changes the state it uses to forward packets.
A MR that acts as a gateway between an entire mobile network and the rest of the Internet has one or more egress interface(s) and one or more ingress interface(s) 🚪 Packets forwarded upstream to the rest of the Internet go out through one of the MR's egress interfaces, and packets forwarded downstream to the mobile network go out through one of the MR's ingress interfaces.
Ingress interface
The interface of a MR that's attached to a link inside the mobile network 🏠
Egress interface
The interface of a MR that's attached to the home link if the MR is at home, or to a foreign link if the MR is in a foreign network 🌍
Mobile Network Node (MNN)
Any node (host or router) located within a mobile network, whether permanently or temporarily. A Mobile Network Node can be either a mobile node or a fixed node 🫧
Access Link (AL)
A last-hop link between a Mobile Node and an Access Point. In other words, it's the facility or medium over which an Access Point and the Mobile Node can communicate at the link layer, which is the layer immediately below IP 📡
Access Point (AP)
An Access Point is a layer 2 device that connects to one or more Access Routers and offers the wireless link connection to the Mobile Node 📶 Access Points are sometimes called base stations or access point transceivers. An Access Point can be a separate entity or co-located with an Access Router.
Radio Cell
The geographical area where an Access Point provides radio coverage, meaning the spot where radio communication between a Mobile Node and that specific Access Point is possible 🌤️
Access Network Router (ANR)
An IP router in the Access Network. An Access Network Router may include Access Network specific functionalities, for example, related to mobility and/or QoS 💖 This is how we tell ordinary routers apart from routers with Access Network-related special functionality.
Access Router (AR)
An Access Network Router that sits on the edge of an Access Network and connects to one or more Access Points. The Access Points can use different technologies 🎀 An Access Router offers IP connectivity to Mobile Nodes and acts as a default router for the Mobile Nodes it's currently serving. It can include intelligence beyond the simple forwarding that ordinary IP routers offer 🧠
Access Network Gateway (ANG)
An Access Network Router that separates an Access Network from other IP networks, much like an ordinary gateway router does 🚧 To the other IP networks, the Access Network Gateway looks like a standard IP router. In a small network, an ANG can also offer the services of an AR, meaning it offers IP connectivity to the mobile nodes too 🫶
Access Network (AN)
An IP network that includes one or more Access Network Routers 🌐
Administrative Domain (AD)
A collection of networks under the same administrative control and grouped together for administrative purposes [5] 🗂️
Serving Access Router (SAR)
The Access Router that's currently offering connectivity to the MN. This is usually where the MN departs from as it makes its way toward a new Access Router, and at that point the Serving Access Router takes on the role of the Previous Access Router 🏃♀️ There may be several Serving Access Routers serving the Mobile Node at the same time 👯
New Access Router (NAR)
The Access Router that offers connectivity to the Mobile Node after a handover 🆕
Previous Access Router (PAR)
An Access Router that offered connectivity to the Mobile Node prior to a handover. This is the Serving Access Router that will cease, or has ceased, to offer connectivity to the Mobile Node 👋 It's also often called the Old Access Router (OAR).
Candidate Access Router (CAR)
An Access Router that the Mobile Node may hand off to. See Section 4.8 🔮
4. Handover Terminology ✨
okay bestie, this section is basically the vocab list for mobility 🦋 these terms describe different angles on keeping a device connected while it moves around. you can sort handovers by their scope, range overlap, performance, diversity, state transitions, mobility type, and control mode 💅
Roaming 🌍
an operator-based term that involves formal agreements between operators, so a mobile can get connectivity from a foreign network 💜 roaming is a particular flavor of user mobility. it covers stuff like users telling the local AN who they are, so inter-AN agreements can kick in and the MN's home network services and applications can show up for the user locally 🎀
Handover 🔁
the process where an active MN (in the Active State, see section 4.6) changes its point of attachment to the network, or the moment such a change is attempted 🦋 the access network may have features that keep sessions in progress from getting interrupted too much ✨ also called handoff 💅
there are different kinds of handover, sorted by the different things involved in them. some of this terminology follows the description in [4] 📚
4.1. Scope of Handover 🗺️
Layer 2 handover 📡
a handover where the MN switches APs (or some other part of the radio channel) connected to the same AR's interface 💖 it's transparent to routing at the IP layer, or it just looks like a link layer reconfiguration with no mobility implications at all 🫶
Intra-AR handover 🏠
a handover that changes the AR's network interface to the mobile. so the Serving AR stays the same, but routing changes inside the AR happen 🧚
Intra-AN handover 🌸
a handover where the MN changes ARs inside the same AN 💅 it isn't necessarily visible outside the AN. but if the ANG serving the MN changes, then it IS seen outside the AN, because the routing paths change 😭 also, the ANG may change for only some of the MN's data flows, not all of them ✨
Inter-AN handover 🚀
a handover where the MN moves to a new AN 💜 this one requires support for macro mobility. it would also have to involve assigning a new IP access address (for example, a new care-of address) to the MN 🎀
Intra-technology handover 🔧
a handover between equipment of the same technology 🍓
Inter-technology handover 🔀
a handover between equipment of different technologies 🌈
Horizontal handover ➡️
this is when MNs move between access points of the same type (in terms of coverage, data rate and mobility), like UMTS to UMTS, or WLAN to WLAN 🌸
Vertical handover ⬆️
this is when MNs move between access points of different types, like UMTS to WLAN 🦋
the line between horizontal and vertical handover is kinda vague, ngl 🙈 for example, going from an AP with an 802.11b WLAN link to an AP with an 802.11g WLAN link could count as either vertical or horizontal, depending on who you ask 💀
also, the IP layer only sees network interfaces and IP addresses, not the specific technologies those interfaces use 🧠 so horizontal and vertical handovers may or may not be noticed at the IP layer. usually a handover can be noticed if the IP address assigned to the interface changes, if the network interface itself changes (which can also change the IP address), or if there's a link outage, like when the mobile node goes out of coverage for a while 📶
for example, in a GPRS network a horizontal handover usually happens completely unnoticed by the IP layer 😌 a WLAN horizontal handover may be noticed if the IP address of the interface changes 💜 on the other hand, vertical handovers often change the network interface, so they tend to get noticed at the IP layer 🔥 still, some specific network cards can switch between access technologies (like GPRS to UMTS) without changing the network interface 🪄
either kind of handover may or may not result in changing the AR, too 💅 for example, an AR could control WLAN and Bluetooth access points, and the mobile node could do horizontal and vertical handovers under that same AR without changing its IP address or even its network interface 👑
4.2. Handover Control 🎮
a handover must be one of the following two types (a) 💖
Mobile-initiated handover 📱
the MN is the one that makes the initial decision to start the handover 🫶
Network-initiated handover 🗼
the network makes the initial decision to start the handover 🌐
a handover is also one of the following two types (b) ✨
Mobile-controlled handover 🕹️
the MN has primary control over the handover process 💜
Network-controlled handover 🎛️
the network has primary control over the handover process 🏰
a handover decision usually involves some kind of measurements about when and where to hand over to 📏 so a handover is also one of these three types (c) 💅
Mobile-assisted handover 🤳
information and measurements from the MN are used by the AR to decide whether to execute a handover 🦋
Network-assisted handover 📡
a handover where the AN collects information that the MN can use in its handover decision 🎀
Unassisted handover 🙅
a handover where neither the MN nor the AR gives any assistance to each other 🫠
note that it's possible for the MN and the AR to both do measurements and make the handover decision 🤝
a handover is also one of the following two types (d) 🌊
Push handover ⬇️
a handover that's either initiated by the PAR, or where the MN starts a handover via the PAR 🌸
Pull handover ⬆️
a handover that's either initiated by the NAR, or where the MN starts a handover via the NAR 🧚
the handover is also either proactive or reactive (e) ⏰
Planned handover 🗓️
a proactive (expected) handover where some signaling can happen before the MN connects to the new AR, like building a temporary tunnel from the previous AR to the new AR 🔮
Unplanned handover 😱
a reactive (unexpected) handover where no signaling happens ahead of the MN's move from the previous AR to the new AR 💀
the five handover types (a-e) are mostly independent of each other, and every handover should be classifiable according to each of these types 🌈
4.3. Simultaneous connectivity to Access Routers 📶
Make-before-break (MBB) 🤝
during an MBB handover, the MN makes the new connection before the old one is broken 💖 so the MN can communicate with the old AR and the new AR at the same time during the handover ✨ this should not be confused with "soft handover," which relies on macro diversity, described in Section 4.5 🦋
Break-before-make (BBM) 💔
during a BBM handover, the MN breaks the old connection before the new connection is made 😤 so the MN cannot communicate with the old AR and the new AR at the same time 🙃
4.4. Performance and Functional Aspects 📊
Handover latency ⏱️
handover latency is the difference between the time a MN was last able to send and/or receive an IP packet by way of the PAR, and the time the MN is able to send and/or receive an IP packet through the NAR 🫧 adapted from [4] 📚
Smooth handover 🧈
a handover that mainly aims to minimize packet loss, with no explicit concern about extra delays in packet forwarding 🌊
Fast handover 🏎️
a handover that mainly aims to minimize handover latency, with no explicit interest in packet loss 💨
Seamless handover 🪡
a handover where there's no change in service capability, security, or quality 💜 in practice, some degradation in service is to be expected 😅 the practical definition of a seamless handover is that other protocols, applications, or end users don't detect any change in service capability, security or quality that would matter to their normal operation 🫶 so what's seamless for one less demanding application might not be seamless for a more demanding one 👀 see [7] for more discussion on the topic 📖
Throughput 🚰
the amount of data from a source to a destination processed by the protocol being measured, for instance IP, TCP, or the MAC protocol 💧 throughput differs between protocol layers 🪜
Goodput 🎯
the total bandwidth used, minus the volume of control messages, protocol overhead from the data packets, and packets dropped due to CRC errors 🧮
Pathloss 📉
a reduction in signal strength caused by traveling through the physical medium that makes up the link 🌫️
Hidden-terminal problem 🫣
the problem where a transmitting node can fail to transmit data because of destructive interference that only the receiving node can detect, not the transmitting node 🕵️
Exposed terminal problem 🙊
the problem where a transmitting node A stops another node B from transmitting, even though node B could have safely transmitted to anyone other than node A 🥺
4.5. Micro Diversity, Macro Diversity, and IP Diversity 🌀
certain air interfaces (for example, the Universal Mobile Telephone System (UMTS) Terrestrial Radio Access Network (UTRAN) running in Frequency Division Duplex (FDD) mode) require, or at least support, macro diversity combining 📻 basically, a single MN can send and receive over two independent radio channels ('diversity branches') at the same time 🤯 the info received over the different branches gets compared, and the info from the better branch gets passed up to the upper layers 🏆 this can improve overall performance, and it can provide a seamless type of handover at layer 2, since a new branch can be added before the old one is deleted 🌷 see also [6] 📚
it's important to tell apart combining/diversity that happens at the physical and radio link layers, where the relevant unit of data is the radio frame, from the kind that happens at layer 3, the network layer, where the IP packet itself is what counts 🧩
in the definitions that follow, micro- and macro diversity refer to protocol layers below the network layer, and IP diversity refers to the network layer 🪞
Micro diversity 🔬
for example, two antennas on the same transmitter send the same signal to a receiver over slightly different paths to fight off fading 📡
Macro diversity 🛰️
duplicating or combining actions that take place over multiple APs, possibly attached to different ARs 🌐 this may need support from the network layer to move the radio frames between the base stations and a central combining point 🏢
IP diversity 💫
the process of duplicating IP packets and sending them to the receiver through more than one point of attachment 🪄 IP allows this semantically because it doesn't guarantee packet uniqueness, and higher-level protocols are assumed to remove duplicates whenever that matters for the application 🧹
4.6. Paging, and Mobile Node States and Modes 💖
okay so, mobile systems can use MN states to run more efficiently without tanking performance 🧚 bestie, the word mode is also super common and means the exact same thing as state, so don't get confused when you see both 💅
A MN is always in exactly one of these three states:
Active state ✨ This is when the AN knows the MN's SAR and the MN can send and receive IP packets. The access link might not be active right now, but the radio layer can set one up without any help from the network layer. The MN has an IP address assigned. main character energy 👑
Dormant state 🌙 In this state the mobile limits its ability to receive normal IP traffic by checking the radio channels way less often. The AN knows the MN's Paging Area, but the MN has no SAR, so packets can't reach the MN unless the AN starts paging. This one is often called Idle state too 🫶
Time-slotted dormant mode ⏰ This is a dormant mode version where the mobile alternates between periods of not listening for any radio traffic and periods of listening for it. Time-slotted dormant mode implementations are typically synchronized with the network, so the network can deliver paging messages to the mobile during the listening periods. it's giving precision 🎀
Inactive state 💤 The MN is in neither the Active nor the Dormant State. It is no longer listening for any packets, not even periodically, and it isn't sending packets either. The MN may be powered off, it may have shut down all interfaces to save a ton of power, or it may be out of range of a radio access point. The MN doesn't necessarily have an IP access address from the AN. 🙈
Note: the MN is in one of these three states, but the AN also stores which state it believes the MN is in. Normally these two match up, and the definitions above assume they do 🦋
Here are some more definitions for paging, building on the state definitions above 🌸
Paging 📣 This is a procedure the Access Network starts to move a Dormant MN into the Active State. After paging, the MN establishes a SAR and the IP routes are set up.
Location updating 📍 This is a procedure the MN starts to tell the AN that it has moved into a new paging area.
Paging area 🗺️ This is a part of the Access Network, usually containing a bunch of ARs/APs, that matches some geographical area. The AN keeps and updates a list of all the Dormant MNs in the area. If the MN is within radio coverage of the area, it can receive paging messages sent within that Paging Area.
Paging area registrations 🛎️ This is signaling from a dormant mode mobile node to the network, used to establish its presence in a new paging area. Paging Area Registrations let the network keep a rough idea of where the mobile is, which is so helpful 🥹
Paging channel 📻 This is a radio channel dedicated to signaling dormant mode mobiles for paging. By current practice, the paging channel only carries the control traffic the radio link needs, although some paging protocols have provision for carrying arbitrary traffic (and so could potentially be used to carry IP).
Traffic channel 🚗 This is the radio channel the IP traffic to an active mobile is typically sent on. A mobile that is actively sending and receiving IP traffic uses it, and it isn't continuously active for a dormant mode mobile. For some radio link protocols, this may be the only channel available.
4.7. Context Transfer 🔁
Context 🧠 This is the information about the current state of a routing-related service that's needed to re-establish that service on a new subnet, without having to do the entire protocol exchange with the MN from scratch. it's giving efficiency 💅
Feature context 🎨 This is the collection of information representing the context for a given feature. The full context associated with a MN is the collection of one or more feature contexts.
Context transfer 🚚 This is the movement of context from one router or other network entity to another, as a way to re-establish routing-related services on a new subnet or collection of subnets.
Routing-related service 🛠️ This is a modification to the default routing treatment of packets to and from the MN. Setting up routing-related services for the first time usually takes a protocol exchange with the MN. An example is header compression. The service may also be indirectly related to routing, like security. Security may not affect the forwarding decision of all intermediate routers, but a packet may be dropped if it fails a security check (can't be encrypted, authentication failed, etc.). Dropping the packet is basically a routing decision 😭 the plot twist!
4.8. Candidate Access Router Discovery 🔍
Capability of an AR 💪 This is a characteristic of the service an AR offers that might interest an MN when the AR is being considered as a handoff candidate.
Candidate AR (CAR) 💜 This is an AR the MN has a choice of performing an IP-level handoff to. It means the MN has the right radio interface to connect to an AP served by this AR, and the coverage of this AR overlaps with the coverage of the AR the MN is currently attached to.
Target AR (TAR) 🎯 This is an AR that the procedures for the MN's IP-level handoff get started with. The TAR is selected after running a TAR Selection Algorithm, which takes into account the capabilities of CARs, the preferences of the MN, and any local policies.
4.9. Types of Mobility 🌍
okay so we can tell apart host mobility and network mobility, plus various types of network mobility 🦋 Terminology that's more about applications, like the Session Initiation Protocol and personal mobility, is out of scope for this document.
Host mobility support 📱 This refers to the function of letting a mobile node change its point of attachment to the network without interrupting IP packet delivery to or from that node. There can be different sub-functions depending on the current level of service being provided. In particular, host mobility support usually implies active and dormant modes of operation, depending on whether the node has any current sessions or not. Access Network procedures are required to keep track of the current point of attachment of all the MNs, or to establish it at will. Accurate location and routing procedures are required in order to maintain the integrity of the communication. Host mobility is often called 'terminal mobility' 🫶
Network mobility support 🚌 This refers to the function of letting an entire network change its point of attachment to the Internet, and therefore its reachability in the topology, without interrupting IP packet delivery to or from that mobile network.
Two subcategories of mobility can be identified within both host mobility and network mobility ✨
Global mobility 🌐 Same as Macro mobility.
Local mobility 🏡 Same as Micro mobility.
Macro mobility 🗺️ This is mobility over a large area. It includes the mobility support and associated address registration procedures that are needed when a MN moves between IP domains. Inter-AN handovers typically involve macro-mobility protocols. Mobile-IP can be seen as a means to provide macro mobility.
Micro mobility 🔬 This is mobility over a small area. Usually this means mobility within an IP domain, with an emphasis on support for active mode using handover, although it may also include idle mode procedures. Micro-mobility protocols exploit the locality of movement by confining movement related changes and signaling to the access network.
Local mobility management 🏠 Local mobility management (LMM) is a generic term for protocols that deal with IP mobility management confined within the access network. LMM messages are not routed outside the access network, although a handover may trigger Mobile IP messages to be sent to correspondent nodes and home agents.
5. Specific Terminology for Mobile Ad-Hoc Networking 🕸️
Cluster 🫧 This is a group of nodes located within close physical proximity, typically all within range of one another, which can be grouped together to limit the production and propagation of routing information.
Cluster head 👑 This is a node (often elected during the cluster formation process) that has complete knowledge about group membership and link state information in the cluster. Each cluster should have one and only one cluster head.
Cluster member 🧁 All nodes within a cluster except the cluster head are called members of that cluster.
Convergence 🤝 This is the process of approaching a state of equilibrium, where all nodes in the network agree on a consistent collection of state about the topology of the network, and where no further control messages are needed to establish the consistency of the network topology.
Convergence time ⏱️ This is the time required for a network to reach convergence after an event (typically, the movement of a mobile node) that changes the network topology.
Laydown 📐 This is the relative physical location of the nodes within the ad hoc network.
Pathloss matrix 📊 This is a matrix of coefficients describing the pathloss between any two nodes in an ad hoc network. When the links are asymmetric, the matrix is also asymmetric.
Scenario 🎬 This is the tuple <laydown, pathloss matrix, mobility factor, traffic>, characterizing a class of ad hoc networks. 🔥
6. Security-related Terminology ✨
okay so this section is the security glossary bit 🔐 It's just the mobility-related slice of the whole security vocab, so we're not getting everything, just the stuff that matters for mobile and wireless networking 💖
Authorization-enabling extension
An authentication that makes a (registration) message acceptable to the ultimate recipient of that registration message. The bestie rule here: an authorization-enabling extension must contain an SPI (see below) [10] 🎀
Mobility security association
A collection of security contexts between a pair of nodes, which may be applied to mobility-related protocol messages exchanged between them. In Mobile IP, each context indicates an authentication algorithm and mode, a secret (a shared key, or an appropriate public/private key pair), and a style of replay protection in use. Mobility security associations may be stored separately from the node's IPsec Security Policy Database (SPD) [10] 🗂️✨
Registration key
A key used in the Mobility Security Association between a mobile node and a foreign agent. It's typically only used once or a very few times, and only for verifying a small volume of Authentication data [12] 🔑 very single-use energy, ngl
Security context
A security context between two nodes defines the manner in which the two nodes choose to mutually authenticate each other, and it indicates an authentication algorithm and mode 🤝💜
Security Parameter Index (SPI)
An index identifying a security context between a pair of routers, picked from the contexts available in the mobility security association 🧚
The Mobile IPv6 specification has more security terminology related to MIPv6 bindings [9] 🦋 Terminology about the MIP challenge/response mechanism is in [11] 💅
7. Security Considerations 🔒
Okay, this one is short but iconic: this document presents only terminology. There are no security issues in this document 🙈 Zero. None. Nada. Full stop.
8. Contributors 🫶
This document was initially based on the work of Tapio Suihko, Phil Eardley, Dave Wisely, Robert Hancock, Nikos Georganopoulos, Markku Kojo, and Jukka Manner 👑
Charles Perkins gave input on terminology related to ad-hoc networks 🌸
Thierry Ernst provided the terminology for discussing mobile networks 🌈
Henrik Levkowetz did a final check of the definitions in revision -05 and suggested a number of changes 📝
9. Acknowledgments 💜
This work has been partially performed in the framework of the IST project IST-2000-28584 MIND, which is partly funded by the European Union 🇪🇺 Some of the authors would like to acknowledge the help of their colleagues in preparing this document, which is so sweet 🥹
Randy Presuhn did a very thorough and helpful review of the -02 version of the terminology. Literally a hero 🦸♀️✨
Some definitions of terminology have been adapted from [1], [2], [3], [4], [7], [8], [9] and [10] 🍓
10. Informative References 📚
[1] Blair, D., Tweedly, A., Thomas, M., Trostle, J. and M. Ramalho, "Realtime Mobile IPv6 Framework", Work in Progress.
[2] Calhoun, P., Montenegro, G. and C. Perkins, "Mobile IP Regionalized Tunnel Management", Work in Progress.
[3] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.
[4] Koodli, R., Ed., "Fast Handovers for Mobile IPv6", Work in Progress.
[5] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for Policy-based Admission Control", RFC 2753, January 2000.
[6] Kempf, J., McCann, P. and P. Roberts, "IP Mobility and the CDMA Radio Access Network: Applicability Statement for Soft Handoff", Work in Progress.
[7] Kempf, J., Ed., "Problem Description: Reasons For Performing Context Transfers Between Nodes in an IP Access Network", RFC 3374, September 2002.
[8] Trossen, D., Krishnamurthi, G., Chaskar, H. and J. Kempf, "Issues in candidate access router discovery for seamless IP-level handoffs", Work in Progress.
[9] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004.
[10] Perkins, C., Ed., "IP Mobility Support for IPv4", RFC 3344, August 2002.
[11] Perkins, C., Calhoun, P. and J. Bharatia, "Mobile IPv4 Challenge/Response Extensions (revised)", Work in Progress.
[12] Perkins, C. and P. Calhoun, "AAA Registration Keys for Mobile IP", Work in Progress.
[13] Ernst, T. and H. Lach, "Network Mobility Support Terminology", Work in Progress.
[14] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
11. Appendix A - Index of Terms 🧾
okay bestie, this is the index, aka the treasure map of every term and where it lives 🗺️✨ every page number is exactly where it should be, no cap 💅
AD ............................................................. 14
AL ............................................................. 13
AN ............................................................. 14
ANG ............................................................ 14
ANR ............................................................ 13
AP ............................................................. 13
AR ............................................................. 14
Access Link .................................................... 13
Access Network ................................................. 14
Access Network Gateway ......................................... 14
Access Network Router .......................................... 13
Access Point ................................................... 13
Access Router .................................................. 14
Active state ................................................... 22
Administrative Domain .......................................... 14
Asymmetric link ................................................. 5
Authorization-enabling extension ............................... 27
BBM ............................................................ 19
BU .............................................................. 3
Bandwidth ....................................................... 2
Bandwidth utilization ........................................... 2
Beacon .......................................................... 3
Binding Update .................................................. 3
Break-before-make .............................................. 19
CAR ............................................................ 15
CAR ............................................................ 24
Candidate AR ................................................... 24
Candidate Access Router ........................................ 15
Capability of an AR ............................................ 24
Care-of-Address ................................................. 3
Channel ......................................................... 3
Channel access protocol ......................................... 3
Channel capacity ................................................ 3
Cluster ........................................................ 26
Cluster head ................................................... 26
Cluster member ................................................. 26
CoA ............................................................. 3
Context ........................................................ 24
Context transfer ............................................... 24
Control message ................................................. 4
Convergence .................................................... 27
Convergence time ............................................... 27
Distance vector ................................................. 4
Dormant state .................................................. 22
Egress interface ............................................... 13
Exposed terminal problem ....................................... 20
FN ............................................................. 12
Fairness ........................................................ 4
Fast handover .................................................. 20
Feature context ................................................ 24
Fixed Node ..................................................... 12
Flooding ........................................................ 4
Foreign subnet prefix ........................................... 4
Forwarding node ................................................. 4
Global mobility ................................................ 25
Goodput ........................................................ 20
HA .............................................................. 5
Handoff ........................................................ 15
Handover ....................................................... 15
Handover latency ............................................... 19
Hidden-terminal problem ........................................ 20
HoA ............................................................. 4
Home Address .................................................... 4
Home Agent ...................................................... 5
Home subnet prefix .............................................. 5
Horizontal Handover ............................................ 16
Host mobility support .......................................... 25
IP access address ............................................... 5
IP diversity ................................................... 21
Inactive state ................................................. 22
Ingress interface .............................................. 12
Inter-AN handover .............................................. 16
Inter-technology handover ...................................... 16
Interface ....................................................... 5
Intra-AN handover .............................................. 16
Intra-AR handover .............................................. 16
Intra-technology handover ...................................... 16
L2 Trigger ...................................................... 6
Laydown ........................................................ 27
Layer 2 handover ............................................... 16
Link ............................................................ 5
Link establishment .............................................. 6
Link state ...................................................... 6
Link-layer trigger .............................................. 6
Link-level acknowledgment ....................................... 6
Local broadcast ................................................. 6
Local mobility ................................................. 25
Local mobility management ...................................... 26
Location updating .............................................. 23
Loop-free ....................................................... 6
MAC ............................................................. 7
MBB ............................................................ 19
MH ............................................................. 12
MN ............................................................. 12
MNN ............................................................ 13
MPR ............................................................. 7
MR ............................................................. 12
Macro diversity ................................................ 21
Macro mobility ................................................. 26
Make-before-break .............................................. 19
Medium Access Protocol .......................................... 7
Micro diversity ................................................ 21
Micro mobility ................................................. 26
Mobile Host .................................................... 12
Mobile Network Node ............................................ 13
Mobile Node .................................................... 12
Mobile Router .................................................. 12
Mobile network ................................................. 12
Mobile network prefix ........................................... 7
Mobile-assisted handover ....................................... 18
Mobile-controlled handover ..................................... 18
Mobile-initiated handover ...................................... 17
Mobility factor ................................................. 7
Mobility security association .................................. 27
Multipoint relay ................................................ 7
NAR ............................................................ 14
Neighbor ........................................................ 7
Neighborhood .................................................... 7
Network mobility support ....................................... 25
Network-assisted handover ...................................... 18
Network-controlled handover .................................... 18
Network-initiated handover ..................................... 17
New Access Router .............................................. 14
Next hop ........................................................ 7
PAR ............................................................ 15
Paging ......................................................... 23
Paging area .................................................... 23
Paging area registrations ...................................... 23
Paging channel ................................................. 23
Pathloss ....................................................... 20
Pathloss matrix ................................................ 27
Payload ......................................................... 8
Planned handover ............................................... 19
Prefix .......................................................... 8
Previous Access Router ......................................... 15
Pull handover .................................................. 18
Push handover .................................................. 18
Radio Cell ..................................................... 13
Registration key ............................................... 28
Roaming ........................................................ 15
Route activation ................................................ 8
Route entry ..................................................... 8
Route establishment ............................................. 8
Routing table ................................................... 8
Routing proxy ................................................... 8
Routing-related service ........................................ 24
SAR ............................................................ 14
SPI ............................................................ 28
Scenario ....................................................... 27
Seamless handover .............................................. 19
Security Parameter Index ....................................... 28
Security context ............................................... 28
Serving Access Router .......................................... 14
Shannon's Law ................................................... 9
Signal strength ................................................. 9
Smooth handover ................................................ 19
Source route .................................................... 9
Spatial re-use .................................................. 9
Subnet .......................................................... 9
System-wide broadcast ........................................... 9
TAR ............................................................ 25
Target AR ...................................................... 25
Throughput ..................................................... 20
Time-slotted dormant mode ...................................... 22
Topology ........................................................ 9
Traffic channel ................................................ 23
Triggered update ................................................10
Unassisted handover ............................................ 18
Unplanned handover ............................................. 19 Vertical handover .............................................. 17Okay, the index wraps up with Vertical handover on page 17 🧚 Now for the people behind the doc! 💖
12. Authors' Addresses 💅
Meet the two bestie authors from the University of Helsinki, Department of Computer Science 🇫🇮🌸
Jukka Manner
Department of Computer Science
University of Helsinki
P.O. Box 26 (Teollisuuskatu 23)
FIN-00014 HELSINKI
Finland
Phone: +358-9-191-44210
Fax: +358-9-191-44441
EMail: jmanner@cs.helsinki.fi Markku Kojo
Department of Computer Science
University of Helsinki
P.O. Box 26 (Teollisuuskatu 23)
FIN-00014 HELSINKI
Finland
Phone: +358-9-191-44179
Fax: +358-9-191-44441
EMail: kojo@cs.helsinki.fi13. Full Copyright Statement 🎀
Okay, the legal bit, but make it cute 🙈 The Internet Society holds the copyright (2004) ✨ This doc is subject to the rights, licenses and restrictions in BCP 78, and except as set forth there, the authors keep all their rights 💜
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Intellectual Property 🦋
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Copies of IPR disclosures sent to the IETF Secretariat, plus any assurances of licenses, or the results of trying to get a general license or permission for implementers or users of this spec, are available from the IETF on-line IPR repository at http://www.ietf.org/ipr 🔥
The IETF invites anyone to flag any copyrights, patents, patent applications, or other proprietary rights that might cover tech needed to implement this standard. Send that info to ietf-ipr@ietf.org 💜
Acknowledgement 🌈
Big thank you to the Internet Society, which currently funds the RFC Editor function ✨ Without that support, none of these docs would be getting polished up for us! 🍓
📦 where this page comes from
- ietf: rfc3753 2004-06
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms