Subject: [Tsvwg] again load sharing

From: giuseppe <[email-masked]>
Date: 09 Apr 2003 11:08:12 +0200

HI. I am investigating the opportunity of load sharing in SCTP. One of
the thing I not undertand is when the load sharing is effective. There
are situations in which load sharing is effective? 
Second, is there anyone who is attempting to response to this question:
when two links are un-shared? In my opinion two link are unshared when
they do not cross same Point Of Congestion. So, detecting at run-time
this event is a very hard challenge....
Giuseppe De Marco
-- 
Giuseppe De Marco
Departement of Electrical and Information Engineering
University of Salerno Italy SA
via ponte don Melillo 1 Fisciano SA
tel: +39 089 964012
mail: [email-masked]

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 9 Apr 2003 03:49:18 -0600

giuseppe,

> are situations in which load sharing is effective? 

Load sharing is effective in any situation where both the available
bandwidth of the network and the offered load exceeds the available
bandwidth of any one interface.  (Or a similar situation with regard
to latency if latency is of concern.)

OTOH the algorithm for load sharing can have interactions with SCTP
protocol mechanisms (retransmission, gaps, SACKs, bundling) and could
reduce efficiency in some circumstances depdending on network
conditions.

IMO algorithms that more closely correspond to SCTP's "primary"
destination approach will have more success than those that deviate
widely from it.  All other factors equal, a sender should not load-share
to a secondary destination until the primary destiation's congestion
window has been sent.  This or similar procedures should have the effect
of grouping as many sequential TSNs as possible to the same destination,
avoiding excess gap detection and reporting due to difference or
variance in OWT between destinations over which traffic is being
loadshared.

> this event is a very hard challenge....

SCTP's congestion procedures do not make assuptions about the underlying
network and are resilient to network changes independent of network
topology.

Where is the challenge?

--brian

-- 
Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
[email-masked]    ¦ world; the unreasonable one persists in  ¦
http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
                        ¦ Therefore  all  progress  depends on the ¦
                        ¦ unreasonable man. -- George Bernard Shaw ¦
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