2000-05-17 Thread David Wang

Hi all,

IS-IS is defined to work with CLNP not for IP originally. Until today a lot
of SONET and telecommunication equipment vendors still use IS-IS to route
CLNP packets through the SONET Data communication channel(DCC) to carry
management information and there is a great pressure to change this to OSPF
and IP. I also know that UUNET runs IS-IS on their network. I never heard
any other networks run IS-IS. Seems I am wrong. My questions are.

1. You guys are talking about using IS-IS in a IP networks not in CLNP
networks. The IS-IS has been modified according to RFC 1195 (Use of OSI
IS-IS for Routing in TCP/IP and Dual Environments) or some other standard.
Is this correct? 

2.  Besides UUNET, which ISPs run IS-IS protocol? Can you name a few? or
what percentage of networks run IS-IS instead of OSPF?


-Original Message-
Sent: Tuesday, May 16, 2000 7:22 AM
Subject: MPLS and IS-IS

Hi all,

I have been hearing IS-IS is a better protocol to be used than OSPF in a
network for TE application. Is that a fair statement? What are the technical

Appreciate if someone can shed some light on this subject.


MPLS and Private Network

2000-04-06 Thread David Wang
Title: MPLS and Private Network

Dear Friends,

A company consists of 2 remotely separated sites, A and B. A leased T1 line connects the networks on these 2 sites together. We generally call the company's network a private network since the connection between the 2 sites are private leased line. 

Now the service provider replace this leased T1 line with a 1.544 mbps MPLS LSP (Label Switched Path). Is this company's network still a private network? Is it still as secure as it was before ? why ? 

We know that the MPLS LSP has gone through many LSR (Label Switch Router) and has been manipulated by the service providers. But the leased T1 line has been manipulated by the service providers too. The signal may be multiplex into DS3, OC-3, OC-12, OC-48, OC-192 then de-multiplex back to OC-48, OC-12, OC-3, DS3, DS1.

Please help me if you know the answers.


Carry IP Packet in Ethernet Frame in IEEE 802.3 LLC Encapsulation Format

2000-03-30 Thread David Wang

Dear Friends,

I never see or heard any product use 802.3 LLC frame format to carry IP
packet. But I am not sure I am correct. Does anyone knows that some product
does use the LLC frame to carry IP packets and why?

There are 2 type of Ethernet frames:
Ethernet Version 2 Frame: 

| destination | source | type | data | fcs|

IEEE 802.3 LLC frame:

| destination | source | length | LLC | org code | type | data |

The key difference is the 2 bytes behind the source MAC address. Using
Ethernet Version 2 Frame, the type field value will large than the maximum
Ethernet frame length 1518. For frames carrying IP packet the type field
value is 0x0800. The interface device driver will check this field and
realize that this frame carries IP packet. It will send the packet to the IP
module for father processing.


How Many Routing Tables

2000-03-23 Thread David Wang

Dear Friends,

This may be a silly question but I never found a clear answer form a book or
a standard. 

A router is running BGP4, OSPF and RIP at the same time. How many routing
tables(or forwarding tables) this router has? I think there should be only
one table produced by all the protocols and used by the router to route
every packet through the router, but I am not sure. Can somebody help get an
answer ?

Thank you very much