Metro Ethernet

[Diego]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello,

I hear a lot these days about ethernet deployment in metropolitan areas
as access networks. Does this mean that there would be one big optical
ethernet LAN (or MAN if you prefer) with fiber to the home connected by
switches? In that case I have a few questions:

1. Wouldn't this lead to massive spanning trees in large cities? One bad
configuration in the network would affect the whole network.

2. Will all IP traffic have to travel to the core even if it is destined
for an intra-MAN destination? I cannot imagine that a ARP broadcast in a
large MAN is feasable.

3. Will these networks co-exist with the current networks, or are they
meant to replace the current infrastructure? In that case will VoIP
replace the POTS? Will the MANs have sufficient QoS to handle voice?

I would appreciate any comments on these questions or your ideas on how
the metro access networks of the future will look like.

Regards,
Diego

-----

diego_daulignac at yahoo dot com
www.aulignac.com

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <crh0tb$k21$1@news.mch.sbs.de>,
Diego <diego_daulignac@yahoo.com.invalid> writes:
>Hello,
>
>I hear a lot these days about ethernet deployment in metropolitan areas
>as access networks. Does this mean that there would be one big optical
>ethernet LAN (or MAN if you prefer) with fiber to the home connected by
>switches? In that case I have a few questions:

No, it usually means using ethernet technology to employ e.g. MPLS
instead of the classical SDH/ATM/MPOA approach.
The scientific community in my city uses such a beast to connect
the respective distributed campi of the participating organisations.
(visit www.brain.de if you do not mind reading german)

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de

 

[Stephen]

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Diego" <diego_daulignac@yahoo.com.invalid> wrote in message
news:crh0tb$k21$1@news.mch.sbs.de...
> Hello,
>
> I hear a lot these days about ethernet deployment in metropolitan areas
> as access networks. Does this mean that there would be one big optical
> ethernet LAN (or MAN if you prefer) with fiber to the home connected by
> switches?

in the UK there are fibre point to point links using ethernet (LAN extension
service, or LES). The BT service is most common and it uses dedicated pair
of fibres per link. You use it as a connection between 2 sites, up to 25 Km
apart, although the costs can go up a lot over more than 5 to 10 Km.

other telcos either use the BT links, or their own Ethernet pipes or a mix
to build more complex networks.

you can transport the ethernet directly on fibre, over SDH, using CWDM or
DWDM to reduce the number of cores, over ATM etc. - all of these are in use
here by various telcos. What you choose depends on how far you need to go,
and how fibre "rich" the supplier is.

Some of these give you a strictly point to point connection, other are more
flexible. so on some SDH gear you may have a point to multipoint style
service, where 1 ethernet port at a central pointhas traffic on multiple
VLANs, and packets from each VLAN may end up at a different port somewhere
in the SDH cloud.

so, you may get your corporate internet feed on a 100M ethernet to the
nearest Pop for your favorite ISP, or it may be an access line to your MPLS
network and so on.

In that case I have a few questions:
>
> 1. Wouldn't this lead to massive spanning trees in large cities? One bad
> configuration in the network would affect the whole network.

you can do this, and some nets have used this in the UK - several school
networks join sites in star or ring topology with ethernet layer 2 switches
to glue it all together (usually to keep the price down).

even where this topology is in use, you normally get a limited group of
users, usually part of the same community, so the layer 2 network is
restricted in size.
>
> 2. Will all IP traffic have to travel to the core even if it is destined
> for an intra-MAN destination? I cannot imagine that a ARP broadcast in a
> large MAN is feasable.

worse yet - imagine a misconfigured set of routers which are replicating
NetBIOS broadcasts by accident - or a loop replicating 100k broadcasts /sec


actually - you just described some of the drawbacks of layer 2 over MPLS -
which is intended to give you an emulated Ethernet, possibly across a
continent.
>
> 3. Will these networks co-exist with the current networks, or are they
> meant to replace the current infrastructure?

Nothing ever replaces all the installed base - these things will co-exist
with conventional networks for a long time, even if they become the
connection of choice.

And here there doesnt seem any prospect of universal broadband in the near
future, never mind a fibre only service - so there should always be a need
for something else. But - it may overtake some types of connection -
anything over 2 Mbps looks to be a possibility.

In that case will VoIP
> replace the POTS?

in the UK BT has announced they want all public PBXes to go Voip - but again
it may take a while (the press release says 10 years - i suspect a lot
longer to get your granny in a remote farmhouse to get rid of an analog
phone)

Will the MANs have sufficient QoS to handle voice?

that bit is doable now.

But an classic ethernet point to point link doesnt need QoS - throw the bits
in 1 end and they fall out the other a fixed time later in the same order.
QoS only has an effect when you have 2 or more packets in a queue and you
need to decide which to send 1st.

it is just the complicated electronics that link the ethernet pipes together
that take account of QoS.
>
> I would appreciate any comments on these questions or your ideas on how
> the metro access networks of the future will look like.

i just wish work would embrace it a bit more quickly - it would make my job
designing networks easier.
>
> Regards,
> Diego
>
> -----
>
> diego_daulignac at yahoo dot com
> www.aulignac.com
--
Regards

Stephen Hope - return address needs fewer xxs

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <oKBDd.109$tq2.12@newsfe2-gui.ntli.net>,
"stephen" <stephen_hope.xx@ntlxworld.com> writes:
>"Diego" <diego_daulignac@yahoo.com.invalid> wrote in message
>news:crh0tb$k21$1@news.mch.sbs.de...
>>
>> 2. Will all IP traffic have to travel to the core even if it is destined
>> for an intra-MAN destination? I cannot imagine that a ARP broadcast in a
>> large MAN is feasable.
>
>worse yet - imagine a misconfigured set of routers which are replicating
>NetBIOS broadcasts by accident - or a loop replicating 100k broadcasts /sec
>
>
>actually - you just described some of the drawbacks of layer 2 over MPLS -
>which is intended to give you an emulated Ethernet, possibly across a
>continent.

Hmm, I don't see why a broadcast storm is worse when it runs over MPLS
than over dark (or colored) fiber. Or over SDH.

And to the OP: An ARP broadcast is always feasable in an Ethernet,
no matter what the spatial dimensions are, othewise it is ill designed.

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de

 

[Stephen]

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Manfred Kwiatkowski" <kwia4000@bronto.zrz.TU-Berlin.DE> wrote in message
news:crn5rr$5l4$1@mamenchi.zrz.TU-Berlin.DE...
> In article <oKBDd.109$tq2.12@newsfe2-gui.ntli.net>,
> "stephen" <stephen_hope.xx@ntlxworld.com> writes:
> >"Diego" <diego_daulignac@yahoo.com.invalid> wrote in message
> >news:crh0tb$k21$1@news.mch.sbs.de...
> >>
> >> 2. Will all IP traffic have to travel to the core even if it is
destined
> >> for an intra-MAN destination? I cannot imagine that a ARP broadcast in
a
> >> large MAN is feasable.
> >
> >worse yet - imagine a misconfigured set of routers which are replicating
> >NetBIOS broadcasts by accident - or a loop replicating 100k broadcasts
/sec
> >
> >
> >actually - you just described some of the drawbacks of layer 2 over
MPLS -
> >which is intended to give you an emulated Ethernet, possibly across a
> >continent.
>
> Hmm, I don't see why a broadcast storm is worse when it runs over MPLS
> than over dark (or colored) fiber. Or over SDH.

it doesnt have to be worse - but it seems that a lot of the new "improved"
WAN services are open to lots of problems that are only traditional on a
LAN.

i also have a problem with treating a large net with relatively long latency
WAN as a LAN without understanding what the side effects will be.
>
> And to the OP: An ARP broadcast is always feasable in an Ethernet,
> no matter what the spatial dimensions are, othewise it is ill designed.
>
> --
> Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de
--
Regards

Stephen Hope - return address needs fewer xxs

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <DERDd.127$BM.65@newsfe1-win.ntli.net>,
"stephen" <stephen_hope.xx@ntlxworld.com> writes:
>"Manfred Kwiatkowski" <kwia4000@bronto.zrz.TU-Berlin.DE> wrote in message
>news:crn5rr$5l4$1@mamenchi.zrz.TU-Berlin.DE...
>> In article <oKBDd.109$tq2.12@newsfe2-gui.ntli.net>,
>> "stephen" <stephen_hope.xx@ntlxworld.com> writes:
>>
>> Hmm, I don't see why a broadcast storm is worse when it runs over MPLS
>> than over dark (or colored) fiber. Or over SDH.
>
>it doesnt have to be worse - but it seems that a lot of the new "improved"
>WAN services are open to lots of problems that are only traditional on a
>LAN.

The more rope the easier to hang yourself
Nevertheless nobody forbids to do things the right way just because
of more economic and flexible hardware.
On the other hand I regret the lack of a native point-to-point
ethernet standard ever since I built my first metro-ethernet back
in '94.

>
>i also have a problem with treating a large net with relatively long latency
>WAN as a LAN without understanding what the side effects will be.

Well I consider the latency issue a myth.
A sensitive application will not run over a WAN either if not helpered,
although I would consider it more of a problem if there existed a beast
like metro-token-ring...

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Manfred Kwiatkowski <kwia4000@bronto.zrz.tu-berlin.de> wrote:
> Well I consider the latency issue a myth.

It probably is. Typical LAN latencies are <10ms, WAN ~50ms.
But LANs can get to 1000+ ms for heavily loaded servers and
should cope. High latency certainly will reduce performace,
but ought not to break things.

> although I would consider it more of a problem if there
> existed a beast like metro-token-ring...

<shudder> That's a gruesome thought!

-- Robert

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

>> although I would consider it more of a problem if there
>> existed a beast like metro-token-ring...
>
> <shudder>  That's a gruesome thought!
>

Metro Arcnet? ;-)

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

James Knott wrote:

> Robert Redelmeier wrote:
>
>>> although I would consider it more of a problem if there
>>> existed a beast like metro-token-ring...
>>
>> <shudder>  That's a gruesome thought!
>>
>
> Metro Arcnet? ;-)

Wasn't FDDI to an extent "metro Token Ring"?

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <crt3tn1d3f@news3.newsguy.com>,
"J. Clarke" <jclarke@nospam.invalid> writes:
>
>Wasn't FDDI to an extent "metro Token Ring"?

Yes, but it was _a_ not _the_ ...

--
Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de

 

[Diego]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Thank's to everybody that responded. Your answers were very helpful and
I think I understand the problem better now.

Regards,
Diego

 

[Michael]

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Manfred Kwiatkowski" <kwia4000@bronto.zrz.TU-Berlin.DE> wrote:
> Diego <diego_daulignac@yahoo.com.invalid> writes:
> >Hello,
> >
> >I hear a lot these days about ethernet deployment in metropolitan areas
> >as access networks. Does this mean that there would be one big optical
> >ethernet LAN (or MAN if you prefer) with fiber to the home connected by
> >switches? In that case I have a few questions:
>
> No, it usually means using ethernet technology to employ e.g. MPLS
> instead of the classical SDH/ATM/MPOA approach.
> The scientific community in my city uses such a beast to connect
> the respective distributed campi of the participating organisations.
> (visit www.brain.de if you do not mind reading german)

Diego, there is a lot of work going on right now in different standard
development organizations, to add features to Ethernet that make it better
suited to the metropolitan networking world. IEEE Std 802.3ah ("Ethernet in
the First Mile") defines a number of new PHYs and an OAM protocol for use in
subscriber access networks. IEEE 802.1 is specifying provider bridges (using
stacked VLANs) and end-to-end OAM for Ethernet, which will solve many of the
issues that are associated with running the metro network as a LAN.

Regards,

Michael
--
Remove "filter" from address to reply.
http://www.ethernetinthefirstmile.com