David,
Juniper networks is motivated to promote RFC 5837 now, as opposed to eleven
years ago, because the deployment of parallel links between routers is becoming
more common
Large network operators frequently require more than 400 Gbps connectivity
between their backbone routers. However, the largest interfaces available can
only handle 400 Gbps. So, parallel links are required. Moreover, it is
frequently cheaper to deploy 4 100 Gbps interfaces than a single 400 Gbps
interface. So, it is not uncommon to see two routers connected by many,
parallel 100 Gbps links. RFC 5837 allows a network operator to trace a packet
interface to interface, as opposed to node to node.
I think that you are correct in saying that:
- LINUX is more likely to be implemented on a host than a router
- Therefore, LINUX hosts will not send RFC 5837 ICMP extensions often
However, LINUX hosts are frequently used in network management stations.
Therefore, it would be very useful if LINUX hosts could parse and display
incoming RFC 5837 extensions, just as they display RFC 4950 ICMP extensions.
Juniper networks plans to support RFC 5837 on one platform in an upcoming
release and on other platforms soon after that.
Ron
Juniper Business Use Only
-----Original Message-----
From: David Ahern <[email protected]>
Sent: Wednesday, March 24, 2021 11:19 PM
To: Ron Bonica <[email protected]>; Zachary Dodds <[email protected]>; Ishaan
Gandhi <[email protected]>
Cc: Andreas Roeseler <[email protected]>; David Miller
<[email protected]>; Network Development <[email protected]>; Stephen
Hemminger <[email protected]>; Willem de Bruijn
<[email protected]>; [email protected]
Subject: Re: rfc5837 and rfc8335
[External Email. Be cautious of content]
On 3/23/21 10:39 AM, Ron Bonica wrote:
> Hi Folks,
>
>
>
> The rationale for RFC 8335 can be found in Section 5.0 of that document.
> Currently, ICMP ECHO and ECHO RESPONSE messages can be used to
> determine the liveness of some interfaces. However, they cannot
> determine the liveness of:
>
>
>
> * An unnumbered IPv4 interface
> * An IPv6 interface that has only a link-local address
>
>
>
> A router can have hundreds, or even thousands of interfaces that fall
> into these categories.
>
>
>
> The rational for RFC 5837 can be found in the Introduction to that
> document. When a node sends an ICMP TTL Expired message, the node
> reports that a packet has expired on it. However, the source address
> of the ICMP TTL Expired message doesn't necessarily identify the
> interface upon which the packet arrived. So, TRACEROUTE can be relied
> upon to identify the nodes that a packet traverses along its delivery
> path. But it cannot be relied upon to identify the interfaces that a
> packet traversed along its deliver path.
>
>
It's not a question of the rationale; the question is why add this support to
Linux now? RFC 5837 is 11 years old. Why has no one cared to add support before
now? What tooling supports it? What other NOS'es support it to really make the
feature meaningful? e.g., Do you know what Juniper products support RFC 5837
today?
More than likely Linux is the end node of the traceroute chain, not the transit
or path nodes. With Linux, the ingress interface can lost in the layers (NIC
port, vlan, bond, bridge, vrf, macvlan), and to properly support either you
need to return information about the right one.
Unnumbered interfaces can make that more of a challenge.
