Subject: RE: [mobile-ip] any deployment?

From: "Bui, Hung" <[email-masked]>
Date: Mon, 17 Jun 2002 16:06:48 -0400

Dear Masataka Ohta San,
 
Thank you again for your interest.
 
Yes, you can have connectivity to the Internet.  You can either tether a PC
to one of our '+' phone or via the iDEN iM1100 modem, please see:
 
http://www.nextel.com/services/nextelonline/index.shtml
<http://www.nextel.com/services/nextelonline/index.shtml> 

Regards,
- Hung

-----Original Message-----
From: Masataka Ohta [  <mailto:[email-masked]>
mailto:[email-masked]]
Sent: Monday, June 17, 2002 12:31 PM
To: Bui, Hung
Cc: 'Pekka Savola'; [email-masked]
Subject: Re: [mobile-ip] any deployment?

Dear Hung Bui;

Are you giving direct internet connectivity to your users with
global IP addresses?

---

From: Masataka Ohta <[email-masked]>
Date: Tue, 18 Jun 2002 10:39:16 +0859 ()

Hung Bui;

> <http://www.nextel.com/services/nextelonline/index.shtml> 

It is still obscure.

"packetstream service" in the page is explained:

	Use your existing applications. Use the same email, browser,
	and other web-enabled applications that are available to you
	    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	in the office. Works especially well with various Wireless
	Business Solutions and third-party applications.

that I have an impression that you are using NAT.

Explanation on "Packetstream Gold service" is same.

However, terms and conditions in iM1100 users' guide says:

: 21. NEXTEL WIRELESS WEB �gGOLD�h SERVICES - Nextel Wireless
: Web �gGold�h Services are those Internet and data Services offered in
: conjunction with a Service plan using the suffix �gGold�h; e.g. PacketStream
: Gold or PowerApps Gold. Company may charge an activation fee for each
: IP address for these Services. These services may be used only with mobile
: clients for Internet/intranet access and Internet e-mail via a standard HTML
: browser (e.g., Netscape Navigator or Communicator, Microsoft Internet
: Explorer, etc.) or proprietary client software for Public Online Service
: Providers (e.g., AOL, CompuServe, ProdigyInternetTM), and related
: mail clients. It may also be used with software for proxy applications (e.g.,
: Citrix), for dispatch applications, for POP3 email access, and for other use
: specifically approved by Nextel. These Internet and data Services may not
: be substituted for a private line or frame relay connection, or be used for
: streaming data feeds. Company reserves the right to deny service, without
: notice, to any Customer whose usage adversely impacts Company�fs
: network, Systems or other subscribers�f use of Services.

that I'm totally confused.

Is "Glod" service somewhat different?

I understand that, at the speed of 56Kbps of "Gold" service, nextel
is afraid that users may use Internet telephony without paying
phone bill.

"for other use specifically approved by Nextel" seems to mean that
you had better use NAT.

Still, contract is meaningful, though not so effective, to suppress
such things as "IP over HTTP".

But, it is equally possible that you give global addresses to ("Gold"
or all) subscribers.

Can you clarify?

Or, can someone living in regions where nextel service is offerred
clarify?

						Masataka Ohta

---

From: Behcet Sarikaya <[email-masked]>
Date: Wed, 19 Jun 2002 16:21:36 -0500

Hello Masataka,
What about your (MIS) deployment of MIP? Can you tell us more about it?
Are you using public addresses with MIPv4 as you mentioned RFC2002?
What is RGW2400?
One comment on your draft, on page 3, you started
During mobile registration,

and nothing followed it?
Regards,

Masataka Ohta wrote:

>: 21. NEXTEL WIRELESS WEB ?gGOLD?h SERVICES - Nextel Wireless
>: Web ?gGold?h Services are those Internet and data Services offered in
>: conjunction with a Service plan using the suffix ?gGold?h; e.g. PacketStream
>: notice, to any Customer whose usage adversely impacts Company?fs
>: network, Systems or other subscribers?f use of Services.
>

-- 
Behcet

---

From: Masataka Ohta <[email-masked]>
Date: Thu, 20 Jun 2002 09:13:32 +0859 ()

Behcet;

> What about your (MIS) deployment of MIP? Can you tell us more about it?

OK.

> Are you using public addresses with MIPv4 as you mentioned RFC2002?

Yes.

> What is RGW2400?

RGW2400 (not a product of MIS) is a router between Ether and 802.11b,
running NetBSD. MIS installed security module on it.

With MIS service, FA is collocated with MN that wireless routers are
not dependent on any mobility protocols.

> During mobile registration,

Thanks. I was adding inessential explanation

	During mobile registration, packets from CH comes from either
	of the access points. As the terminal recieves packets from
	both access points, there is no packet loss caused by
	the latency of the registration.

I will add it to the next version.
						Masataka Ohta

---

From: Behcet Sarikaya <[email-masked]>
Date: Thu, 20 Jun 2002 09:28:44 -0500

Masataka,
  Thanks for the info. I am glad to hear that MIPv4 is being deployed.
Two transceivers (which emulate cellular networks' use of multiple 
physical channels) on each MN might cause interference, more so if so 
many are placed in the same cell. Do you agree with this?
    Regards,

-- 
Behcet

---

From: Masataka Ohta <[email-masked]>
Date: Fri, 21 Jun 2002 09:46:09 +0859 ()

Behcet 

>   Thanks for the info. I am glad to hear that MIPv4 is being deployed.

I'm glad too to deploy it on the commercial Internet.

> many are placed in the same cell. Do you agree with this?

I'm not sure what is your issue.

Just as two (or more) hosts on a single 10base 5 cable interfere
each other, when they simultaneously transmit, two (or more ) MNs
on a single WLAN with a certain frequence/code interfere.

CSMA/CD and CSMA/CA are the technology to suppress the simultaneous
transmittion, even if the number of hosts is large.

So, the number of MNs in a same cell is irrelevent, though expected
share of bandwidth to each host is, of course, reduced accordingly.

In addition, WLAN has a mechanism of ACK and retransmission,
to reduce the effect of interference from other hosts using
other frequency bands, for which CSMA/CA may not work so
efficiently.

OK?

Then, with the proposed smooth handover solution with WLAN,
two transceivers are considered to be, at the link layer,
two hosts using different frequency bands to be taken
care of by the existing mechanisms of WLAN.

On PHS, two transceivers use different physical channels.

It's a difference between best effort WLAN and QoS assured PHS.

							Masataka Ohta

---

From: Gerald Maguire <[email-masked]>
Date: Fri, 21 Jun 2002 20:48:18 +0200 (MET DST)

Masataka Ohta said:
      ...

There are really several cases:
1. a mobile equipped with two WLAN interfaces which are using
   different "channels" (this could be different spreading codes,
   different frequencies, hoping sequences etc.)
   
   In this case they are two independent interfaces with very little
   interference with each other.

      With different spreading codes, but in the same frequency band -
      the transmission by one will probably wipe out the reception by the
      other - because unless you have a very wide dynamic range receiver
      the AGC will be saturated by the tranmission by the near by
      transmitter.

      When in different frequency bands, there will be some interference
      because the tail of the one band may leak power into the adjacent
      channel.

      When using different hopping sequences they will occasionally hop
      to the same frequency and thus interfere with each other.

      When one is hopping and the other using direct sequence spread
      spectrum (DSSS), the hopper will interfere when it hops into the
      the DSSS interface's channel and the DSSS can interfere with
      many of the channels the hopper can hop to. Note in the case of
      801.11 if you have several DSSS systems operating so that you
      are operating in all the 2.4 GHz channels, then the hopper will
      always be interfering with one of them.

2. a mobile equipped with two WLAN interfaces which are using
   the same "channels", but associated with different access points.
   They will compete for the channel as usual -- since there is only
   one channel.

3. there is a chance that both interfaces could be searching for a new
   AP at the same time and both pick the same new "channel" and AP --
   in which case they can interfere as per item 2 above. So you need
   some way to prevent them from both going to the same channel.

An interesting device is a two way WLAN interface + a receive only
WLAN interface - the later can be used to identify new potential APs
while you continue to use the two way interface for
communication. Authentication, Registration, ... could be done with a
new AP via the existing AP and the other WLAN interface - through the
fixed network.

However, it is clear that because of the effects of 1, 2, and 3 you
would want to have the drivers for two WLAN interfaces communicating
with each other - rather than having them completely independent.

Consider the case where you have already given a number of packets to
the driver for transmission, if this interface is no longer able to
deliver frames to the old AP - then if the new AP interface is up and
on the same subnet it may be feasible to simply move all the IP packets
over to the outgoing queue for the new interface. Unless you have
integrated the drivers you will not be able to do this optimization
since the packets are already below the IP layer. Is this case likely?
Yes, I think that if we look at current campus and many single
operator settings the adjacent cells are often on the same subnet.
{You can already see this sort of behavior if you force a mobile to
switch between the two interfaces of an Orinoco Wavepoint II AP - the
AP will actually output the frames on the other interface when it sees
the mobile appear on its other WLAN interface.}

Chip

---

From: Masataka Ohta <[email-masked]>
Date: Sat, 22 Jun 2002 09:32:46 +0859 ()

Chip;

>       the AGC will be saturated by the tranmission by the near by

The most serious interference occurs if a packet arrives to a
terminal, while the terminal is transmitting, which is usual
with plain WLAN without smooth handover or mobility.

So, WLAN is designed to tolerate interferences.

>    They will compete for the channel as usual -- since there is only

That is a degenerate case, where just a single transciever is
necessary.

Actually, our trial in early days use a single channel that this
is the case.

The downside is that we can not utilize all the bandwidth allocated
to WLAN and that we can not modify a band of an access point
to avoid noise frequencies local to the access point.

>    some way to prevent them from both going to the same channel.

MIS does not use L2 functionalities of WLAN for beacon generation
or frequency scanning, because these L2 functinalities, contrary
to naive expectations, increases handover latency even on terminals
with only one transceiver, explanation of which is being added to
the draft.

So, almost evenrything is controlled by the terminal L3 software
and L2 is mostly for CSMA/CA.

> WLAN interface - the later can be used to identify new potential APs

A problem is that it takes considerable amount of time to set
transmission frequency band and to reset to the original with
currently available WLAN NIC, during which receiving is
not possible, which is why MIS use two transmitters.

> since the packets are already below the IP layer. Is this case likely?

With a single receiver, handover is initiated only after
signal quality from the current AP considerably degrade, in which
case, it may be too late to push all the packets in buffer to
the current AP.

With dual receivers, handover is initiated if signal quality from
the current AP considerably weaker than a new AP. With slightly
overlapping areas of APs, it is expected that a handover is initiated
long before the communication with the current AP become impossible
(even if you are moving at 60Km/h, you move 16.6m/s). Assuming
effective speed of 11M WLAN is 5M, 5 mega bits of buffer is drained
in a second that your case is unlikely.

> the mobile appear on its other WLAN interface.}

Link layer is an intermediate entity between end systems.

An AP is an intermediate entity between end systems.

Thus, too much link layer or AP intelligence is against the
end to end principle and is harmful to the Internet.

						Masataka Ohta