Subject: load distribution and smoothing when route flaps

From: Jing Shen <[email-masked]>
Date: Wed, 23 Jul 2003 20:55:21 +0800

Hi, (' spamcontrol ')

In past days, we talked with someone from one of the
main ISP in China. He present us a question as: how to
smooth load migration when the primary outgoing link
goes down? The network topo. could be abbreviated as:

   Secondary outgoing link           backup link
    -----                      ------
         \                   /
          \                 /
          --------------------
          |     AS (OSPF)    |
          --------------------
                  |
                  | primary outgoing link
                  |

In normal state, about 90% outgoing traffic flows
through primary outgoing link, 10% or less on
Secondary link.( the bandwidht of primary is times of
secondary link, which is more than backup link)

The problem comes when primary outgoing link goes
down. At this time, they(ISP engineers) have to
redirect traffic to backup link and secondary link
manually if the other two links are needed to be used,
or only secondary link will carry all traffic. When
primary link comes up, the phenomenon is: neary all
traffic migrates to primary link and load on primary
link may reach 100% or so.

the questions:

1. How does those ISPs around make full use of
outgoing link capacity as well as guaranteeing service
quality?

2. Is there any method proposed to smooth traffic
migration in either intra-AS or inter-AS situation?
How does those ISPs deal with such situation?

3. Although DiffServ has been discussed for years,
they do not deploy it. Why should we talk so much
about DS-TE ?

4. We've spent a lot time with e2e policy around, but
if the traffic delivery method is kept to very simple
one, is that skeptible to achive a cost-effective and
high performance network without introducing more
intellenge into core networks?

thanks a lot.

regards

=====
Jing Shen

State Key Lab of CAD&CG
ZheJiang University(YuQuan)
HangZhou, ZheJiang Province 310027
P.R.China

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