We want to aggregate flows using MPLS labeling
sob., 7 lip 2018 o 00:51 Ben Pfaff napisał(a):
> An MPLS packet, from an OVS datapath perspective, only has a few fields
> anyway:
>
> - Ethernet source and destination.
> - Ethertype is always the MPLS ethertype.
> - Optional VLAN tag(s).
> - MPLS labels?
>
> What's the value of leaving out those other fields?
>
> On Sat, Jul 07, 2018 at 12:39:02AM +0200, Grzegorz wrote:
> > OK, so I suppose for my purposes I need two separate hash tables in EMC:
> > one regular and one just for MPLS matching.
> > Or may I procced like this?
> > if (packet with MPLS label!=0)
> > zeroes all fileds except MPLS header and compute hash
> > else
> > regular hash
> >
> > pt., 6 lip 2018 o 23:54 Ben Pfaff napisał(a):
> >
> > > Leaving data that will be used in a key comparison out of the hash will
> > > also cause hash collisions.
> > >
> > > On Thu, Jul 05, 2018 at 11:31:06PM +0200, Grzegorz wrote:
> > > > Ok, I agree. We don't want to change a hash function but only the
> input
> > > to
> > > > it, i.e., we want that hash will be computed based only on label
> number
> > > in
> > > > our case in microflow cache. Of course for such the hash the label
> number
> > > > can be used itself as a hash value.
> > > >
> > > > Regarding proposed mechanism, let say that we have some class of
> flows
> > > that
> > > > should be treated in network in same way, i.e., that are directed to
> the
> > > > same point in the network. Please consider such the simple network:
> > > >
> > > > n1---|
> > > > |--n3---n4
> > > > n2---|
> > > >
> > > > (n1 -> n3, n2->n3, n3->4 if picture is not clear)
> > > >
> > > > Let's consider a situation when n1 and n2 want to send a packet to
> n4. So
> > > > n1 stores one flow in microcache, n2 stores one flow in microcache,
> n3
> > > > stores 2 flows in its microcache and same n4. If n1 and n2 (or rather
> > > host
> > > > connected to them) will generate 3 different flows directed to n4,
> the
> > > > number of flows in each node (switch) will be tripled.
> > > > But if all nodes (controlled by OF controller) will use same label to
> > > reach
> > > > a particular node in the network, the number of flows will be as
> follows
> > > > (in case of 3 flows originated in n1 and n2):
> > > > n1: 3 flows, matches based on 5tuple, all with same actions, i.e.
> > > MPLS=400,
> > > > out=1
> > > > n2: 3 flows, matches based on 5tuple, all with same actions, i.e.
> > > MPLS=400,
> > > > out=1
> > > > n3: 1 flow, match based on mpls label and proper action to send out
> to
> > > > proper interface.
> > > > This is a simple case, but when a network is complicated number of
> flows
> > > in
> > > > core (in this case n3) switches may be reduced.
> > > >
> > > > This approach is used simultaneously with multipath transmission
> > > approach.
> > > > Please look into figure 2 and section IIB on the page 6 of
> > > > https://arxiv.org/pdf/1805.07993.pdf for some explanation.
> > > >
> > > >
> > > >
> > > > czw., 5 lip 2018 o 22:59 Ben Pfaff napisał(a):
> > > >
> > > > > Typically, changing a hash function in this way will only increase
> the
> > > > > number of hash collisions without reducing the number of hash table
> > > > > entries.
> > > > >
> > > > > On Thu, Jul 05, 2018 at 10:49:03PM +0200, Grzegorz wrote:
> > > > > > Sure, but we want to examine how a number of flows is reduced
> when
> > > > > proposed
> > > > > > mechanism is implemented. If we use what is now available in
> ovs, it
> > > will
> > > > > > still generate thousands of flows (hashes) in Exact Match Cache.
> > > Please
> > > > > > correct me if I'm wrong
> > > > > >
> > > > > > czw., 5 lip 2018 o 22:41 Ben Pfaff napisał(a):
> > > > > >
> > > > > > > You can match on MPLS flows without needing to modify OVS's
> kernel
> > > flow
> > > > > > > table structure. Why do you want to modify it?
> > > > > > >
> > > > > > > On Thu, Jul 05, 2018 at 09:25:05PM +0200, Grzegorz wrote:
> > > > > > > > The goal is to minimize number of flows (aggregate them) in
> the
> > > core
> > > > > of
> > > > > > > > network using some labeling. In our case MPLS is proposed
> but any
> > > > > other
> > > > > > > > technique allowing for labeling may be used, e.g. VLANs.
> This is
> > > > > part of
> > > > > > > s
> > > > > > > > bigger idea. Details are presented in paper
> > > > > > > > https://arxiv.org/pdf/1805.07993.pdf
> > > > > > > >
> > > > > > > > czw., 5 lip 2018 o 21:15 Ben Pfaff napisał(a):
> > > > > > > >
> > > > > > > > > It's an odd change. What's the goal?
> > > > > > > > >
> > > > > > > > > On Thu, Jul 05, 2018 at 08:27:08PM +0200, Grzegorz wrote:
> > > > > > > > > > I'm taking about hash based on which flow table is
> looked up
> > > in
> > > > > > > kernel
> > > > > > > > > data
> > > > > > > > > > path.
> > > > > > > > > >
> > > > > > > > > > czw., 5 lip 2018 o 20:20 Ben Pfaff
> napisał(a):
> > > > > > > > > >
> > > > > > > > > > >
