分享
 
 
 

RFC2290 - Mobile-IPv4 Configuration Option for PPP IPCP

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

Network Working Group J. Solomon

Request for Comments: 2290 Motorola

Updates: 2002 S. Glass

Category: Standards Track FTP Software

February 1998

Mobile-IPv4 Configuration Option for PPP IPCP

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.

Abstract

Mobile IP [RFC2002] defines media-independent procedures by which a

Mobile Node can maintain existing transport and application-layer

connections despite changing its point-of-attachment to the Internet

and without changing its IP address. PPP [RFC1661] provides a

standard method for transporting multi-protocol packets over point-

to-point links. As currently specified, Mobile IP Foreign Agents

which support Mobile Node connections via PPP can do so only by first

assigning unique addresses to those Mobile Nodes, defeating one of

the primary advantages of Foreign Agents. This documents corrects

this problem by defining the Mobile-IPv4 Configuration Option to the

Internet Protocol Control Protocol (IPCP) [RFC1332]. Using this

option, two peers can communicate their support for Mobile IP during

the IPCP phase of PPP. Familiarity with Mobile IP [RFC2002], IPCP

[RFC1332], and PPP [RFC1661] is assumed.

Table of Contents

1. IntrodUCtion . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.1. Specification Language . . . . . . . . . . . . . . . . . 2

1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . 2

1.3. Problem Statement . . . . . . . . . . . . . . . . . . . 3

1.4. Requirements . . . . . . . . . . . . . . . . . . . . . . 5

2. Mobile-IPv4 Configuration Option . . . . . . . . . . . . . . . 6

2.1. Option Format . . . . . . . . . . . . . . . . . . . . . 6

2.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3. High-Level Requirements for Non-Mobile-Nodes . . . . . . 7

2.4. High-Level Requirements for Mobile Nodes . . . . . . . . 8

2.5. Detailed Description . . . . . . . . . . . . . . . . . . 8

2.6. Example Scenarios . . . . . . . . . . . . . . . . . . . 12

3. Additional Requirements . . . . . . . . . . . . . . . . . . . 14

3.1. Other IPCP Options . . . . . . . . . . . . . . . . . . . 14

3.2. Move Detection . . . . . . . . . . . . . . . . . . . . . 14

4. Security Considerations . . . . . . . . . . . . . . . . . . . 15

5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16

7. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 16

8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 17

1. Introduction

Mobile IP [RFC2002] defines protocols and procedures by which

packets can be routed to a mobile node, regardless of its current

point-of-attachment to the Internet, and without changing its IP

address. Mobile IP is designed to run over any type of media and any

type of data link-layer. However, the interaction between Mobile IP

and PPP is currently underspecified and generally results in an

inappropriate application of Mobile IP when mobile nodes connect to

the Internet via PPP.

This document defines proper interaction between a mobile node [RFC

2002] and a peer through which the mobile node connects to the

Internet using PPP. This requires the definition of a new option for

IPCP [RFC1332], named the "Mobile-IPv4" Configuration Option, which

is defined in this document. The mobile node and the peer use this

option to negotiate the appropriate use of Mobile IP over the PPP

link.

The Mobile-IPv4 option defined in this document is intended to work

in conjunction with the existing IP-Address option [RFC1332].

1.1. Specification Language

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 RFC2119.

1.2. Terminology

This document uses the following terms as defined in [RFC2002]:

Mobile Node

A host or router that changes its point-of-attachment from one

link to another. A mobile node may change its location without

changing its IP address; it may continue to communicate with

other Internet nodes at any location using its (permanent)

home, IP address, assuming link-layer connectivity is available

at its current location.

Home Agent

A router with at least one interface on a mobile node's home

link. A home agent intercepts packets destined to a mobile

node's home address and tunnels them to the mobile node's

care-of address when the mobile node is connected to a foreign

link. A mobile node informs its home agent of its current

care-of address through an authenticated registration protocol

defined by Mobile IP.

Foreign Agent

A router with at least one interface on a mobile node's

(current) foreign link. When a mobile node uses a foreign

agent's care-of address, the foreign agent detunnels and

delivers packets to the mobile node that were tunneled by the

mobile node's home agent. A foreign agent might also serve as

a default router for packets sent by a registered mobile node.

Peer

The PPP peer of a mobile node. The mobile node's peer might

support home agent functionality, foreign agent functionality,

both, or neither.

1.3. Problem Statement

In Mobile IP, packets sent to a mobile node's home address are routed

first to the mobile node's home agent, a router on the mobile node's

home link which intercepts packets sent to the home address. The

home agent then tunnels such packets to the mobile node's care-of

address, where the packets are extracted from the tunnel and

delivered to the mobile node. There are two types of care-of

addresses:

Co-located Care-of Address

An address temporarily assigned to a mobile node itself. In this

case, the mobile node is the exit-point of the tunnel and

decapsulates packets encapsulated for delivery by its home agent.

A Co-located Care-of Address may be used by exactly one mobile

node at any point in time.

Foreign Agent Care-of Address

An address of a foreign agent that has at least one interface on a

mobile node's visited, foreign link. In this case, the foreign

agent decapsulates packets that have been tunneled by the home

agent and delivers them to the mobile node over the visited link.

A Foreign Agent Care-of Address may be used simultaneously by many

mobile nodes at any point in time.

In Appendix B, Mobile IP [RFC2002] currently specifies only the

following with respect to PPP:

"The Point-to-Point-Protocol (PPP) [RFC1661] and its Internet

Protocol Control Protocol (IPCP) [RFC1332], negotiates [sic] the

use of IP addresses.

"The mobile node SHOULD first attempt to specify its home address,

so that if the mobile node is attaching to its home [link], the

unrouted link will function correctly. When the home address is

not accepted by the peer, but a transient IP address is

dynamically assigned to the mobile node, and the mobile node is

capable of supporting a co-located care-of address, the mobile

node MAY register that address as a co-located care-of address.

When the peer specifies its own IP address, that address MUST NOT

be assumed to be a foreign agent care-of address or the IP address

of a home agent."

Inspection of this text reveals that there is currently no way for

the mobile node to use a foreign agent care-of address, without first

being assigned a unique IP address, even if the peer also supports

foreign agent functionality. The reason for this can be seen by

walking through the IPCP negotiation:

1. A mobile node connects to a peer via PPP and proposes its home

address in an IPCP Configure-Request containing the IP-Address

option. In this scenario, we assume that the mobile node is

connecting to some foreign link.

2. The peer has no way of knowing whether this Configure-Request was

received from: (a) a mobile node proposing its home address; or

(b) a conventional node proposing some topologically non-routable

address. In this case, the peer must (conservatively) send a

Configure-Nak of the IP-Address option supplying a topologically

appropriate address for use by the node at the other end of the

PPP link.

3. The mobile node, in turn, has no way of knowing whether this

Configure-Nak was received because the peer is a foreign agent

being conservative, or because the peer does not implement Mobile

IP at all. Therefore, the mobile node must (conservatively)

assume that the peer does not implement Mobile IP and continue

the negotiation of an IP address in IPCP, after which point the

mobile node can use the assigned address as a co-located care-of

address.

Here we observe that, even if the mobile node's peer is a foreign

agent and sends an Agent Advertisement to the mobile node after IPCP

reaches the Opened state, the mobile node will still have negotiated

a routable address in step 3, which it is likely already using as a

co-located care-of address. This defeats the purpose of foreign

agent care-of addresses, which are designed to be shared by multiple

mobile nodes and to eliminate the need to assign a unique address to

each mobile node.

1.4. Requirements

The purpose of this document is to specify the behavior of both ends

of the PPP link when one or more of the PPP peers supports Mobile IP.

Specifically, the design of the option and protocol defined in this

document is based upon the following requirements:

1. The option and protocol described in this document must be

backwards compatible with conventional nodes and their potential

peers which do not implement this option nor any Mobile IP

functionality.

2. The option and protocol described in this document must

accommodate a variety of scenarios, minimally those provided in

the examples of Section 2.6.

3. The option and protocol described in this document must not

duplicate any functionality already defined in other IPCP

options; specifically, the IP-Address option.

4. A unique address must not be assigned to a mobile node unless

absolutely necessary. Specifically, no such address is assigned

to a mobile node that connects via PPP to its home link or a

mobile node that connects via PPP to a foreign agent (and uses

that foreign agent's care-of address).

2. Mobile-IPv4 Configuration Option

This section defines the Mobile-IPv4 Configuration Option and

provides several examples of its use.

2.1. Option Format

The Mobile-IPv4 Configuration Option for IPCP is defined as follows:

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type Length Mobile Node's ...

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

... Home Address

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type

4 (Mobile-IPv4)

Length

6 (The length of this entire extension in bytes)

Mobile Node's Home Address

In a Configure-Request, the IP home address of the mobile node

sending this Configuration Option, otherwise the (unmodified) IP

home address of the mobile node when sent in a Configure-Ack or

Configure-Reject. Configure-Nak'ing this option is undefined and

MUST NOT be sent by implementations complying with this version of

the specification. This field MUST NOT be zero.

Default Value

The Mobile-IPv4 Configuration Option defaults to the sending

mobile node's home address.

In describing the operation of the Mobile-IPv4 Configuration Option

(in conjunction with the IP-Address Configuration Option), we use the

following abbreviations:

PPP Message Types:

Request = Configure-Request

Reject = Configure-Reject

Ack = Configure-Ack

Nak = Configure-Nak

IPCP Configuration Options:

MIPv4 = Mobile-IPv4

IP = IP-Address

IP addresses:

a.b.c.d = some non-zero IP address

w.x.y.z = some non-zero IP address other than a.b.c.d

home = a mobile node's IP Home address

coa = an IP Care-Of Address

0 = the all-zeroes IP address (0.0.0.0)

2.2. Overview

The Mobile-IPv4 Configuration Option is designed to be used in

conjunction with the IP-Address Configuration Option. For the

convenience of implementors, the detailed description in section 2.5

includes all possible combinations of these two options that might be

sent by a PPP peer during IPCP. Along with each possibility is a

description of how the receiver should interpret the contents as well

as a suggested course of action.

2.3. High-Level Requirements for Non-Mobile-Nodes

A node that is not performing mobile node functionality (such as

non-Mobile-IP-aware nodes as well as nodes performing only home agent

functionality, foreign agent functionality, or both) MUST NOT include

a Mobile-IPv4 Configuration Option within any Configure-Request

message. As per [RFC1332], such a node SHOULD send a Configure-

Request containing an IP-Address Configuration Option in which the

IP-Address field is set to a non-zero IP address that the node has

assigned to one of its interfaces. If an eXPlicit IP address has

been assigned to the node's PPP interface then this address SHOULD be

sent in preference to any of the node's other addresses.

A node MUST NOT send a Configure-Nak containing a Mobile-IPv4

Configuration Option. Doing so is currently "undefined" and might

cause interoperability problems when a useful meaning for Configure-

Nak is ultimately defined for the Mobile-IPv4 Configuration Option.

A node that sends a Configure-Ack containing a Mobile-IPv4

Configuration Option SHOULD send an Agent Advertisement [RFC2002]

immediately upon IPCP for that link entering the Opened state.

2.4. High-Level Requirements for Mobile Nodes

A mobile node SHOULD begin its IPCP negotiation by sending the

Configure-Request described in either item #1 or item #4 in Section

2.5. The mobile node MAY begin its negotiation with one of the other

numbered items in Section 2.5 under extenuating circumstances.

A mobile node that receives a Configure-Ack containing a Mobile-IPv4

Configuration Option MUST receive an Agent Advertisement, possibly in

response to an Agent Solicitation, before sending a Registration

Request [RFC2002] if that mobile node is connecting to a foreign

link. This is because the peer might be a foreign agent that

enforces a policy which requires a mobile node to register with that

foreign agent even if the mobile node is using a co-located care-of

address. A mobile node need not wait for such an advertisement if it

connects to its home link. See item 7a in section 2.5 for one way in

which a mobile node can determine if it has connected to its home

link. Another way is by receiving an explicit notification of this

fact from its peer, such as receipt of the messages in items 1b, 2c,

and 3a in section 2.5.

A mobile node that receives a Configure-Reject containing a Mobile-

IPv4 Configuration Option SHOULD fall back to IPCP negotiation using

the IP-Address option [RFC1332]. A mobile node SHOULD begin this

negotiation with Request(IP=home) or Request(IP=0), depending on

whether or not the mobile node is connecting to its home link,

respectively. A mobile node MAY make this determination by

inspection of an IP-Address option contained within a Configure-

Request sent by its peer. If the prefix of the peer's stated IP-

address is equal to the prefix of the mobile node's home address,

then the mobile node MAY conclude that it is connecting to its home

link. Otherwise, if the mobile node is connecting to a foreign link,

then the mobile node SHOULD send Request(IP=0) since its peer might

have no means for assigning addresses other than IPCP. This

specification therefore updates this behavior as described in [RFC

2002], the latter of which recommends that a mobile node begin IP-

Address negotiation with Request(IP=Home) under all circumstances.

A peer that is performing neither home agent nor foreign agent

functionality SHOULD send a Reject in response to any Request

received from its peer that contains a Mobile-IPv4 Configuration

Option.

2.5. Detailed Description

The numbered items below show all possible combinations of Mobile-

IPv4 and IP-Address Configuration Options that a mobile node (or a

conventional node) might send to its peer. Mobile nodes SHOULD begin

their IPCP negotiation with item #1 or item #4 depending on whether

they prefer a co-located or a foreign agent care-of address

respectively. The lettered items list the possible legal responses

that a peer might send to the mobile node (or conventional node) in

response to the numbered Request.

In each case, an interpretation is defined and a suggested course of

action is provided. Finally, it is believed that the presentation

below has the advantages of conciseness and precision in comparison

to an equivalent presentation in "prose form."

1. Request(IP=0,MIPv4=home) means "I prefer a co-located care-of

address to a foreign agent care-of address." Peer MUST respond

with one of the following:

a. Nak(IP=coa) means "use coa as your co-located care-of

address". Goto 2.

b. Nak(IP=home) means "you're at home and don't need a care-of

address". Goto 3.

c. Reject(IP=0) means "I cannot assign a co-located care-of

address but you're welcome to use me as a foreign agent".

Goto 4.

d. Reject(MIPv4=home) means "I do not implement the Mobile-IPv4

option". If the peer also sent Request(IP=address) and the

prefix of the peer's assigned address is equal to that of the

mobile node's home address, then goto 6 with a.b.c.d=home;

otherwise, goto 5.

e. Reject(IP=0,MIPv4=home) means "use the default". Goto 7.

=> Ack(IP=0, ...), Nak(MIPv4=any, ...) MUST NOT be sent.

2. Request(IP=coa,MIPv4=home) means "I want to use coa as my co-

located care-of address." Peer MUST respond with one of the

following:

a. Ack(IP=coa,MIPv4=home) means "ok, use coa as your co-located

care-of address; be sure to wait for an advertisement."

Opened.

b. Nak(IP=alternate-coa) means "no, use alternate-coa as your

co-located care-of address". Goto 2.

c. Nak(IP=home) means "you're at home and don't need a co-

located care-of address". Goto 3.

d. Reject(IP=coa) means "coa is not a useful value for a co-

located care-of address on this link and I cannot assign a

useful one (or I will not negotiate the IP-Address option) --

you may use me as a foreign agent". Goto 4.

e. Reject(MIPv4=home) means "I do not implement the Mobile-IPv4

option". If the peer also sent Request(IP=address) and the

prefix of the peer's address is equal to that of the mobile

node's home address, then goto 6 with a.b.c.d=home;

otherwise, goto 5.

f. Reject(IP=coa,MIPv4=home) means "use the default". Goto 7.

=> Nak(MIPv4=any, ...) MUST NOT be sent.

3. Request(IP=home,MIPv4=home) means "I think I'm at home but if I'm

wrong then I prefer a co-located care-of address to a foreign

agent care-of address." Peer MUST respond with one of the

following:

a. Ack(IP=home,MIPv4=home) means "yes, you're at home". Opened.

b. Nak(IP=coa) means "you're not at home, use coa as your co-

located care-of address". Goto 2.

c. Reject(IP=home) means "you're not at home and I cannot assign

a co-located care-of address (or I will not negotiate the

IP-Address option) -- you may use me as a foreign agent".

Goto 4.

d. Reject(MIPv4=home) means "I do not implement the Mobile-IPv4

option". If the peer also sent Request(IP=address) and the

prefix of the peer's address is equal to that of the mobile

node's home address, then goto 6 with a.b.c.d=home;

otherwise, goto 5.

e. Reject(IP=home,MIPv4=home) means "use the default". Goto 7.

=> Nak(MIPv4=any, ...) MUST NOT be sent.

4. Request(MIPv4=home) means "I want to run Mobile IP over this link

and I don't want a co-located care-of address." Peer MUST respond

with one of the following:

a. Ack(MIPv4=home) means "ok, wait for an advertisement to

figure out where you are." Opened.

b. Reject(MIPv4=home) means "I do not implement the Mobile-IPv4

option". If the peer also sent Request(IP=address) and the

prefix of the peer's address is equal to that of the mobile

node's home address, then goto 6 with a.b.c.d=home;

otherwise, goto 5.

=> Nak(MIPv4=any, ...) MUST NOT be sent.

5. Request(IP=0) means "Please assign an address/co-located-care-

of-address". Peer MUST respond with one of the following:

a. Nak(IP=a.b.c.d) means "use a.b.c.d as your address/co-

located-care-of-address". Goto 6.

b. Reject(IP=0) means "I cannot assign an address (for the

Mobile Node to use as a co-located-care-of-address), or I do

not implement the IP-Address option". Goto 7.

=> Ack(IP=0) MUST NOT be sent and historically means "I don't

know your address either". Opened. An implementation MUST

NOT use 0 as its IP address upon receiving Ack(IP=0) but MAY

use some other, non-zero, interface address for packets sent

on its PPP interface.

6. Request(IP=a.b.c.d) means "I want to use a.b.c.d as my

address/home-address/co-located-care-of-address". Peer MUST

respond with one of the following:

a. Ack(IP=a.b.c.d) means "ok, a.b.c.d is your address/home-

address/co-located-care-of-address". Opened.

b. Nak(IP=w.x.y.z) means "no, use w.x.y.z as your address/home-

address/co-located-care-of-address". Goto 6.

c. Reject(IP=a.b.c.d) means "a.b.c.d is a bad address to use,

but I cannot give you a good one" or "I do not implement the

IP-Address option". Goto 7.

7. Request() means "I want to use the default". Peer MUST respond

with one of the following:

a. Ack() means "ok, use the default". Opened.

In this case the mobile node will use the "default" values of

the IP-Address option (no address configured by IPCP) and the

Mobile-IPv4 option (the mobile node's IP home address). The

mobile node SHOULD send Agent Solicitations to see if there

are any agents present on the current link. (Note that the

current "link" might also include a shared medium if the

mobile node's PPP peer is a bridge.) If an agent is present

and the mobile node receives an Agent Advertisement, then the

mobile node employs its move-detection algorithm(s) and

registers accordingly.

In any case, if the mobile node's peer supplied an IP-Address

option containing a non-zero value within an IPCP Configure-

Request, the mobile node MAY use this address to determine

whether or not it is connected to its home link. This can be

accomplished by comparing the stated IP address with the

mobile node's home address under the prefix-length associated

with the home link. If the mobile node is connected to its

home link then it SHOULD de-register with its home agent.

Otherwise, the mobile node MAY attempt to oBTain a

topologically routable address through any of its supported

means (e.g., DHCP, manual configuration, etc.) for use as a

co-located care-of address. If the mobile node is successful

in obtaining such an address then it SHOULD register this

address with its home agent.

=> Nak(IP=0) MUST NOT be sent. Goto 6.

=> Nak() MUST NOT be sent.

=> Reject() MUST NOT be sent.

2.6. Example Scenarios

This section illustrates the use of the option and protocol as

defined in the previous sections. In the examples which follow, a

Configure-Request sent by a mobile node and the response generated by

the peer are shown on the same line. The number and letter to the

left of each request/response refer to the numbered and lettered

items in Section 2.5.

A. A mobile node prefers a co-located care-of address and the peer

is a foreign agent that is capable of assigning such an address:

(1)(a) Request(IP=0,MIPv4=Home) / Nak(IP=coa)

(2)(a) Request(IP=coa,MIPv4=Home) / Ack(IP=coa,MIPv4=Home)

- Mobile node waits to receive an Agent Advertisement.

- If (Advertisement has R-bit set) then

Mobile node registers using co-located care-of address via

the foreign agent;

else

Mobile node registers using co-located care-of address

directly with its home agent.

B. A mobile node prefers a co-located care-of address and the peer

is a foreign agent that cannot assign a co-located care-of

address (e.g., it has no pool of addresses from which to allocate

for the purpose of assignment):

(1)(c) Request(IP=0,MIPv4=Home) / Reject(IP=0)

(4)(a) Request(MIPv4=Home) / Ack(MIPv4=Home)

- IPCP completes.

- Mobile node waits to receive an Agent Advertisement.

- Mobile node registers using the peer's foreign agent care-of

address with its home agent.

C. A mobile node prefers a co-located care-of address and the peer

determines that the mobile node's home address is such that the

mobile node is connecting to its home link:

(1)(b) Request(IP=0,MIPv4=Home) / Nak(IP=Home)

(3)(a) Request(IP=Home,MIPv4=Home) / Ack(IP=Home,MIPv4=Home)

- IPCP completes.

- Mobile node de-registers with its home agent.

D. A mobile node prefers a foreign agent care-of address and the

peer is a foreign agent which finds this state of affairs

satisfactory:

(4)(a) Request(MIPv4=Home) / Ack(MIPv4=Home)

- IPCP completes.

- Mobile node waits to receive an Agent Advertisement.

- Mobile node registers using the peer's foreign agent care-of

or de-registers at home, depending on the values in the Agent

Advertisement.

E. A mobile node prefers a co-located care-of address and the peer

does not implement the Mobile-IPv4 Configuration Option. The

peer is, however, capable of assigning dynamic addresses:

(1)(d) Request(IP=0,MIPv4=Home) / Reject(MIPv4=Home)

(5)(a) Request(IP=0) / Nak(IP=a.b.c.d)

(6)(a) Request(IP=a.b.c.d) / Ack(IP=a.b.c.d)

- IPCP completes.

- Mobile node registers using a.b.c.d as a co-located care-of

address with its home agent.

F. A mobile node prefers a co-located care-of address and the peer

does not implement the Mobile-IPv4 Configuration Option. The peer

is not capable of assigning dynamic addresses:

(1)(e) Request(IP=0,MIPv4=Home) / Reject(IP=0,MIPv4=Home)

(7)(a) Request() / Ack()

- IPCP completes.

- Mobile node sends an Agent Solicitation and/or attempts to

obtain a co-located care-of address via means outside IPCP

(e.g., DHCP or manual configuration), or it gives up.

3. Additional Requirements

3.1. Other IPCP Options

A mobile node MUST NOT include the deprecated IP-Addresses option in

any Configure-Request that contains a Mobile-IPv4 option, an IP-

Address option, or both.

Conversely, the mobile node MAY include an IP-Compression-Protocol

option and any other options that do not involve the negotiation of

IP addresses.

If a mobile node and a foreign agent or a home agent agree in IPCP to

use Van Jacobson Header Compression [RFC1144], then the mobile node

MUST NOT set the 'V' bit in its ensuing Mobile IP Registration

Request [RFC2002]. If the PPP peer entities are utilizing VJ header

compression there is no gain for the mobile ip entities to do so, and

requesting this option is likely to cause confusion.

3.2. Move Detection

Mobile nodes that connect via PPP MUST correctly implement PPP's

IPCP, since movement by the mobile node will likely change its PPP

peer. Specifically, mobile nodes MUST be prepared to renegotiate

IPCP at any time, including, the renegotiation of the IP-Address

Configuration Option and the Mobile-IPv4 Configuration Option

described in this document. As per [RFC1661], a mobile node in the

Opened state MUST renegotiate IPCP upon receiving an IPCP Configure-

Request from its peer.

Also note that certain wireless links can employ handoff and proxying

mechanisms that would not necessarily require bringing down a PPP

link but would indeed require a mobile node to register with a new

foreign agent. Therefore, mobile nodes which connect to an agent via

PPP MUST employ their move detection algorithms (see section 2.4.2 in

[RFC2002]) and register whenever they detect a change in

connectivity.

Specifically, a mobile node that fails to receive an Agent

Advertisement within the Lifetime advertised by its current foreign

agent, MUST assume that it has lost contact with that foreign agent

(see Section 2.4.2.1, [RFC2002]). If, in the mean time, the mobile

node has received Agent Advertisements from another foreign agent,

the mobile node SHOULD immediately register with that foreign agent

upon timing out with its current foreign agent.

Likewise, a mobile node that implements move detection based upon the

Prefix-Length Extension MUST compare the prefix of any advertising

agents with that of its current foreign agent (see Section 2.4.2.2,

[RFC2002]). If such a mobile node receives an Agent Advertisement

from a foreign agent specifying a different prefix than that of its

current foreign agent, then the mobile node that employs this method

of move detection MUST register with that new foreign agent.

A mobile node MAY treat PPP link-establishment as a sufficient reason

to proceed with a new Mobile IP registration. Section 2 defines the

circumstances under which mobile nodes MUST wait for an Agent

Advertisement before registering. Accordingly, foreign agents and

home agents SHOULD send an Agent Advertisement over a PPP link

immediately after IPCP for that link enters the Opened state.

4. Security Considerations

This document introduces no known security threats over and above

those facing any node on the Internet that either connects via PPP or

implements Mobile IP or both. Specifically, service providers should

use cryptographically strong authentication (e.g., CHAP [RFC1994])

to prevent theft-of-service. Additionally, users requiring

confidentiality should use PPP link encryption [RFC1968], IP-layer

encryption [RFC1827], or application-layer encryption, depending

upon their individual requirements. Finally, Mobile IP

authentication [RFC2002] protects against trivial denial-of-service

attacks that could otherwise be waged against a mobile node and its

home agent.

5. References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate

Requirement Levels", BCP 14, RFC2119, March 1997.

[RFC1144] Jacobson, V., "Compressing TCP/IP Headers for Low-Speed

Serial Links", RFC1144, January 1990.

[RFC1332] McGregor, G., "The PPP Internet Protocol Control Protocol

(IPCP)," RFC1332, May 1992.

[RFC1661] Simpson, W., Editor, "The Point-to-Point Protocol (PPP)

for the Transmission of Multi-protocol Datagrams over Point-to-

Point Links", STD 51, RFC1661, July 1994.

[RFC1827] Atkinson, R., "IP Encapsulating Security Payload (ESP)",

RFC1827, August 1995.

[RFC1994] Simpson, W., "PPP Challenge Handshake Authentication

Protocol (CHAP)", RFC1994, August 1996.

[RFC1968] Meyer, G., "The PPP Encryption Control Protocol (ECP)",

RFC1968, June 1996.

[RFC2002] Perkins, C., Editor, "IP Mobility Support", RFC2002,

October 1996.

6. Acknowledgments

The design of this protocol and option were inspired by an earlier

submission by B. Patel and C. Perkins, then of IBM, in a now expired

internet draft. Also, some of William Simpson's text was copied

verbatim from [RFC1661] in order to ensure consistency of

terminology and specification. The same goes for some of Charlie

Perkins' definitions, and other relavent text, from [RFC2002].

Tim Wilson and Chris Stanaway (Motorola) contributed significantly to

the design of this Configuration Option and protocol specification.

Special thanks to Vernon Schryver (SGI), Craig Fox (Cisco), Karl Fox

(Ascend), and John Bray (FTP) for their helpful suggestions,

comments, and patience.

7. Authors' Addresses

Jim Solomon

Motorola, Inc.

1301 E. Algonquin Rd. - Rm 2240

Schaumburg, IL 60196

Phone: +1-847-576-2753

Fax: +1-847-576-3240

EMail: solomon@comm.mot.com

Steven Glass

FTP Software, Inc.

2 High Street

North Andover, MA 01845

Phone: +1-508-685-4000

Fax: +1-508-684-6105

EMail: glass@ftp.com

8. Full Copyright Statement

Copyright (C) The Internet Society (1998). All Rights Reserved.

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

 
 
 
免责声明:本文为网络用户发布,其观点仅代表作者个人观点,与本站无关,本站仅提供信息存储服务。文中陈述内容未经本站证实,其真实性、完整性、及时性本站不作任何保证或承诺,请读者仅作参考,并请自行核实相关内容。
2023年上半年GDP全球前十五强
 百态   2023-10-24
美众议院议长启动对拜登的弹劾调查
 百态   2023-09-13
上海、济南、武汉等多地出现不明坠落物
 探索   2023-09-06
印度或要将国名改为“巴拉特”
 百态   2023-09-06
男子为女友送行,买票不登机被捕
 百态   2023-08-20
手机地震预警功能怎么开?
 干货   2023-08-06
女子4年卖2套房花700多万做美容:不但没变美脸,面部还出现变形
 百态   2023-08-04
住户一楼被水淹 还冲来8头猪
 百态   2023-07-31
女子体内爬出大量瓜子状活虫
 百态   2023-07-25
地球连续35年收到神秘规律性信号,网友:不要回答!
 探索   2023-07-21
全球镓价格本周大涨27%
 探索   2023-07-09
钱都流向了那些不缺钱的人,苦都留给了能吃苦的人
 探索   2023-07-02
倩女手游刀客魅者强控制(强混乱强眩晕强睡眠)和对应控制抗性的关系
 百态   2020-08-20
美国5月9日最新疫情:美国确诊人数突破131万
 百态   2020-05-09
荷兰政府宣布将集体辞职
 干货   2020-04-30
倩女幽魂手游师徒任务情义春秋猜成语答案逍遥观:鹏程万里
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案神机营:射石饮羽
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案昆仑山:拔刀相助
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案天工阁:鬼斧神工
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案丝路古道:单枪匹马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:与虎谋皮
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:李代桃僵
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:指鹿为马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:小鸟依人
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:千金买邻
 干货   2019-11-12
 
推荐阅读
 
 
 
>>返回首頁<<
 
靜靜地坐在廢墟上,四周的荒凉一望無際,忽然覺得,淒涼也很美
© 2005- 王朝網路 版權所有