diff --git a/Cargo.lock b/Cargo.lock
index 6d6038a449..3667469f95 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -135,14 +135,15 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "atty"
-version = "0.2.13"
+version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
+ "hermit-abi 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -326,7 +327,7 @@ dependencies = [
 
 [[package]]
 name = "blake2b_simd"
-version = "0.5.9"
+version = "0.5.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "arrayref 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -494,7 +495,7 @@ version = "2.33.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -561,7 +562,7 @@ name = "colored"
 version = "1.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -666,7 +667,7 @@ name = "criterion"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "cast 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "criterion-plot 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -963,7 +964,7 @@ dependencies = [
  "clear_on_drop 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "curve25519-dalek 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1025,7 +1026,7 @@ name = "env_logger"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "humantime 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1037,7 +1038,7 @@ name = "env_logger"
 version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "humantime 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1131,7 +1132,7 @@ dependencies = [
  "lru 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "slog 2.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "slog-async 2.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "slog-stdlog 4.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1161,7 +1162,7 @@ dependencies = [
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.16.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hex 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-test 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1296,7 +1297,7 @@ dependencies = [
  "fixed-hash 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "impl-rlp 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "impl-serde 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "primitive-types 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "primitive-types 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "uint 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1325,7 +1326,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "synstructure 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1538,7 +1539,7 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.5"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1708,7 +1709,7 @@ name = "impl-codec"
 version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "parity-scale-codec 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-scale-codec 1.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1727,6 +1728,14 @@ dependencies = [
  "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "impl-serde"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "serde 1.0.104 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.3.0"
@@ -1945,7 +1954,7 @@ dependencies = [
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.16.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "rw-stream-sink 0.1.2 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-executor 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-io 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1962,7 +1971,7 @@ version = "0.13.0"
 source = "git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e#c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e"
 dependencies = [
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1998,7 +2007,7 @@ dependencies = [
  "parity-multihash 0.2.0 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rlp 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-io 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-timer 0.2.12 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2053,7 +2062,7 @@ dependencies = [
  "lru 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "protobuf 2.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-codec 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-io 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2097,7 +2106,7 @@ dependencies = [
  "parity-multihash 0.2.0 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)",
  "protobuf 2.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "smallvec 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-codec 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-io 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2216,7 +2225,7 @@ dependencies = [
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.16.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "rw-stream-sink 0.1.2 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-codec 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-io 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "twofish 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2319,7 +2328,7 @@ dependencies = [
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "hmac-drbg 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "subtle 2.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "typenum 1.11.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2334,7 +2343,7 @@ dependencies = [
  "digest 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "hmac-drbg 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "subtle 2.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "typenum 1.11.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2436,7 +2445,7 @@ dependencies = [
 
 [[package]]
 name = "lock_api"
-version = "0.3.2"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2756,7 +2765,7 @@ name = "num_cpus"
 version = "1.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "hermit-abi 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hermit-abi 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2850,15 +2859,15 @@ dependencies = [
  "blake2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "bytes 0.4.12 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha-1 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha-1 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "sha3 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "unsigned-varint 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "parity-scale-codec"
-version = "1.1.0"
+version = "1.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "arrayvec 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2896,7 +2905,7 @@ name = "parking_lot"
 version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "lock_api 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lock_api 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot_core 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2976,13 +2985,13 @@ dependencies = [
 
 [[package]]
 name = "primitive-types"
-version = "0.6.1"
+version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "fixed-hash 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "impl-codec 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "impl-rlp 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "impl-serde 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "impl-serde 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "uint 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2993,7 +3002,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -3472,7 +3481,7 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "base64 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "blake2b_simd 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "blake2b_simd 0.5.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "crossbeam-utils 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -3624,7 +3633,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -3652,7 +3661,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -3679,7 +3688,7 @@ dependencies = [
 
 [[package]]
 name = "sha-1"
-version = "0.8.1"
+version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3695,7 +3704,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "sha2"
-version = "0.8.0"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3721,7 +3730,7 @@ name = "simple_logger"
 version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "chrono 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "colored 1.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -3810,7 +3819,7 @@ name = "slog-term"
 version = "2.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "chrono 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "slog 2.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "term 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4019,7 +4028,7 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.12"
+version = "1.0.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4045,7 +4054,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -4767,7 +4776,7 @@ dependencies = [
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-shared 0.2.56 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -4810,7 +4819,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-backend 0.2.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-shared 0.2.56 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -4852,7 +4861,7 @@ dependencies = [
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen-backend 0.2.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "weedle 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -5037,7 +5046,7 @@ dependencies = [
  "mio 0.6.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "mio-extras 2.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "sha-1 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sha-1 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -5143,7 +5152,7 @@ dependencies = [
 "checksum arrayvec 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cff77d8686867eceff3105329d4698d96c2391c176d5d03adc90c7389162b5b8"
 "checksum asn1_der 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6fce6b6a0ffdafebd82c87e79e3f40e8d2c523e5fea5566ff6b90509bf98d638"
 "checksum asn1_der_derive 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0d0864d84b8e07b145449be9a8537db86bf9de5ce03b913214694643b4743502"
-"checksum atty 0.2.13 (registry+https://github.com/rust-lang/crates.io-index)" = "1803c647a3ec87095e7ae7acfca019e98de5ec9a7d01343f611cf3152ed71a90"
+"checksum atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
 "checksum autocfg 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "1d49d90015b3c36167a20fe2810c5cd875ad504b39cff3d4eae7977e6b7c1cb2"
 "checksum backtrace 0.3.40 (registry+https://github.com/rust-lang/crates.io-index)" = "924c76597f0d9ca25d762c25a4d369d51267536465dc5064bdf0eb073ed477ea"
 "checksum backtrace-sys 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)" = "5d6575f128516de27e3ce99689419835fce9643a9b215a14d2b5b685be018491"
@@ -5156,7 +5165,7 @@ dependencies = [
 "checksum bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 "checksum bitvec 0.15.2 (registry+https://github.com/rust-lang/crates.io-index)" = "a993f74b4c99c1908d156b8d2e0fb6277736b0ecbd833982fd1241d39b2766a6"
 "checksum blake2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "94cb07b0da6a73955f8fb85d24c466778e70cda767a568229b104f0264089330"
-"checksum blake2b_simd 0.5.9 (registry+https://github.com/rust-lang/crates.io-index)" = "b83b7baab1e671718d78204225800d6b170e648188ac7dc992e9d6bddf87d0c0"
+"checksum blake2b_simd 0.5.10 (registry+https://github.com/rust-lang/crates.io-index)" = "d8fb2d74254a3a0b5cac33ac9f8ed0e44aa50378d9dbb2e5d83bd21ed1dc2c8a"
 "checksum block-buffer 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c0940dc441f31689269e10ac70eb1002a3a1d3ad1390e030043662eb7fe4688b"
 "checksum block-cipher-trait 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1c924d49bd09e7c06003acda26cd9742e796e34282ec6c1189404dee0c1f4774"
 "checksum block-padding 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "fa79dedbb091f449f1f39e53edf88d5dbe95f895dae6135a8d7b881fb5af73f5"
@@ -5256,7 +5265,7 @@ dependencies = [
 "checksum hashbrown 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8e6073d0ca812575946eb5f35ff68dbe519907b25c42530389ff946dc84c6ead"
 "checksum heapsize 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1679e6ea370dee694f91f1dc469bf94cf8f52051d147aec3e1f9497c6fc22461"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
-"checksum hermit-abi 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f629dc602392d3ec14bfc8a09b5e644d7ffd725102b48b81e59f90f2633621d7"
+"checksum hermit-abi 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "eff2656d88f158ce120947499e971d743c05dbcbed62e5bd2f38f1698bbc3772"
 "checksum hex 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "805026a5d0141ffc30abb3be3173848ad46a1b1664fe632428479619a3644d77"
 "checksum hex 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "023b39be39e3a2da62a94feb433e91e8bcd37676fbc8bea371daf52b7a769a3e"
 "checksum hkdf 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3fa08a006102488bd9cd5b8013aabe84955cf5ae22e304c2caf655b633aefae3"
@@ -5275,6 +5284,7 @@ dependencies = [
 "checksum impl-codec 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "1be51a921b067b0eaca2fad532d9400041561aa922221cc65f95a85641c6bf53"
 "checksum impl-rlp 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8f7a72f11830b52333f36e3b09a288333888bf54380fd0ac0790a3c31ab0f3c5"
 "checksum impl-serde 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "58e3cae7e99c7ff5a995da2cf78dd0a5383740eda71d98cf7b1910c301ac69b8"
+"checksum impl-serde 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5bbe9ea9b182f0fb1cabbd61f4ff9b7b7b9197955e95a7e4c27de5055eb29ff8"
 "checksum indexmap 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712d7b3ea5827fcb9d4fda14bf4da5f136f0db2ae9c8f4bd4e2d1c6fde4e6db2"
 "checksum integer-sqrt 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "ea155abb3ba6f382a75f1418988c05fe82959ed9ce727de427f9cfd425b0c903"
 "checksum iovec 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "b2b3ea6ff95e175473f8ffe6a7eb7c00d054240321b84c57051175fe3c1e075e"
@@ -5320,7 +5330,7 @@ dependencies = [
 "checksum linked-hash-map 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "ae91b68aebc4ddb91978b11a1b02ddd8602a05ec19002801c5666000e05e0f83"
 "checksum lock_api 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "62ebf1391f6acad60e5c8b43706dde4582df75c06698ab44511d15016bc2442c"
 "checksum lock_api 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ed946d4529956a20f2d63ebe1b69996d5a2137c91913fe3ebbeff957f5bca7ff"
-"checksum lock_api 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e57b3997725d2b60dbec1297f6c2e2957cc383db1cebd6be812163f969c7d586"
+"checksum lock_api 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "79b2de95ecb4691949fea4716ca53cdbcfccb2c612e19644a8bad05edcf9f47b"
 "checksum log 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e19e8d5c34a3e0e2223db8e060f9e8264aeeb5c5fc64a4ee9965c062211c024b"
 "checksum log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)" = "14b6052be84e6b71ab17edffc2eeabf5c2c3ae1fdb464aae35ac50c67a44e1f7"
 "checksum lru 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)" = "5d8f669d42c72d18514dfca8115689c5f6370a17d980cb5bd777a67f404594c8"
@@ -5357,7 +5367,7 @@ dependencies = [
 "checksum parity-codec 3.5.4 (registry+https://github.com/rust-lang/crates.io-index)" = "2b9df1283109f542d8852cd6b30e9341acc2137481eb6157d2e62af68b0afec9"
 "checksum parity-multiaddr 0.6.0 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)" = "<none>"
 "checksum parity-multihash 0.2.0 (git+https://github.com/SigP/rust-libp2p/?rev=c0c71fa4d7e6621cafe2c087d1aa1bc60dd9116e)" = "<none>"
-"checksum parity-scale-codec 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "f9f9d99dae413590a5f37e43cd99b94d4e62a244160562899126913ea7108673"
+"checksum parity-scale-codec 1.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f747c06d9f3b2ad387ac881b9667298c81b1243aa9833f086e05996937c35507"
 "checksum parity-send-wrapper 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "aa9777aa91b8ad9dd5aaa04a9b6bcb02c7f1deb952fca5a66034d5e63afc5c6f"
 "checksum parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ab41b4aed082705d1056416ae4468b6ea99d52599ecf3169b00088d43113e337"
 "checksum parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "fa7767817701cce701d5585b9c4db3cdd02086398322c1d7e8bf5094a96a2ce7"
@@ -5370,7 +5380,7 @@ dependencies = [
 "checksum pkg-config 0.3.17 (registry+https://github.com/rust-lang/crates.io-index)" = "05da548ad6865900e60eaba7f589cc0783590a92e940c26953ff81ddbab2d677"
 "checksum ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
 "checksum primitive-types 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2288eb2a39386c4bc817974cc413afe173010dc80e470fcb1e9a35580869f024"
-"checksum primitive-types 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a0253db64c26d8b4e7896dd2063b516d2a1b9e0a5da26b5b78335f236d1e9522"
+"checksum primitive-types 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e4336f4f5d5524fa60bcbd6fe626f9223d8142a50e7053e979acdf0da41ab975"
 "checksum proc-macro-hack 0.5.11 (registry+https://github.com/rust-lang/crates.io-index)" = "ecd45702f76d6d3c75a80564378ae228a85f0b59d2f3ed43c91b4a69eb2ebfc5"
 "checksum proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)" = "cf3d2011ab5c909338f7887f4fc896d35932e29146c12c8d01da6b22a80ba759"
 "checksum proc-macro2 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)" = "0319972dcae462681daf4da1adeeaa066e3ebd29c69be96c6abb1259d2ee2bcc"
@@ -5441,9 +5451,9 @@ dependencies = [
 "checksum serde_repr 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "cd02c7587ec314570041b2754829f84d873ced14a96d1fd1823531e11db40573"
 "checksum serde_urlencoded 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)" = "642dd69105886af2efd227f75a520ec9b44a820d65bc133a9131f7d229fd165a"
 "checksum serde_yaml 0.8.11 (registry+https://github.com/rust-lang/crates.io-index)" = "691b17f19fc1ec9d94ec0b5864859290dff279dbd7b03f017afda54eb36c3c35"
-"checksum sha-1 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "23962131a91661d643c98940b20fcaffe62d776a823247be80a48fcb8b6fce68"
+"checksum sha-1 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f7d94d0bede923b3cea61f3f1ff57ff8cdfd77b400fb8f9998949e0cf04163df"
 "checksum sha1 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2579985fda508104f7587689507983eadd6a6e84dd35d6d115361f530916fa0d"
-"checksum sha2 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7b4d8bfd0e469f417657573d8451fb33d16cfe0989359b93baf3a1ffc639543d"
+"checksum sha2 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "27044adfd2e1f077f649f59deb9490d3941d674002f7d062870a60ebe9bd47a0"
 "checksum sha3 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)" = "dd26bc0e7a2e3a7c959bc494caf58b72ee0c71d67704e9520f736ca7e4853ecf"
 "checksum simple_logger 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "109facdf91db4b79de557313b5e031f0f8a86373e316bf01158190aa68bcc74e"
 "checksum slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "17b4fcaed89ab08ef143da37bc52adbcc04d4a69014f4c1208d6b51f0c47bc23"
@@ -5472,7 +5482,7 @@ dependencies = [
 "checksum subtle 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2d67a5a62ba6e01cb2192ff309324cb4875d0c451d55fe2319433abe7a05a8ee"
 "checksum subtle 2.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7c65d530b10ccaeac294f349038a597e435b18fb456aadd0840a623f83b9e941"
 "checksum syn 0.15.44 (registry+https://github.com/rust-lang/crates.io-index)" = "9ca4b3b69a77cbe1ffc9e198781b7acb0c7365a883670e8f1c1bc66fba79a5c5"
-"checksum syn 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)" = "ddc157159e2a7df58cd67b1cace10b8ed256a404fb0070593f137d8ba6bef4de"
+"checksum syn 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)" = "1e4ff033220a41d1a57d8125eab57bf5263783dfdcc18688b1dacc6ce9651ef8"
 "checksum synstructure 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)" = "02353edf96d6e4dc81aea2d8490a7e9db177bf8acb0e951c24940bf866cb313f"
 "checksum synstructure 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)" = "67656ea1dc1b41b1451851562ea232ec2e5a80242139f7e679ceccfb5d61f545"
 "checksum take_mut 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f764005d11ee5f36500a149ace24e00e3da98b0158b3e2d53a7495660d3f4d60"
diff --git a/beacon_node/eth2-libp2p/src/rpc/handler.rs b/beacon_node/eth2-libp2p/src/rpc/handler.rs
index 31a0ba3e1e..19c752a7b8 100644
--- a/beacon_node/eth2-libp2p/src/rpc/handler.rs
+++ b/beacon_node/eth2-libp2p/src/rpc/handler.rs
@@ -1,7 +1,7 @@
 #![allow(clippy::type_complexity)]
 #![allow(clippy::cognitive_complexity)]
 
-use super::methods::{RPCErrorResponse, RequestId};
+use super::methods::{ErrorMessage, RPCErrorResponse, RequestId, ResponseTermination};
 use super::protocol::{RPCError, RPCProtocol, RPCRequest};
 use super::RPCEvent;
 use crate::rpc::protocol::{InboundFramed, OutboundFramed};
@@ -28,7 +28,8 @@ pub const RESPONSE_TIMEOUT: u64 = 10;
 /// The number of times to retry an outbound upgrade in the case of IO errors.
 const IO_ERROR_RETRIES: u8 = 3;
 
-/// Inbound requests are given a sequential `RequestId` to keep track of.
+/// Inbound requests are given a sequential `RequestId` to keep track of. All inbound streams are
+/// identified by their substream ID which is identical to the RPC Id.
 type InboundRequestId = RequestId;
 /// Outbound requests are associated with an id that is given by the application that sent the
 /// request.
@@ -72,8 +73,8 @@ where
     /// Map of outbound items that are queued as the stream processes them.
     queued_outbound_items: FnvHashMap<RequestId, Vec<RPCErrorResponse>>,
 
-    /// Sequential Id for waiting substreams.
-    current_substream_id: RequestId,
+    /// Sequential ID for waiting substreams. For inbound substreams, this is also the inbound request ID.
+    current_inbound_substream_id: RequestId,
 
     /// Maximum number of concurrent outbound substreams being opened. Value is never modified.
     max_dial_negotiated: u32,
@@ -153,7 +154,7 @@ where
             outbound_substreams: FnvHashMap::default(),
             inbound_substreams_delay: DelayQueue::new(),
             outbound_substreams_delay: DelayQueue::new(),
-            current_substream_id: 1,
+            current_inbound_substream_id: 1,
             max_dial_negotiated: 8,
             keep_alive: KeepAlive::Yes,
             inactive_timeout,
@@ -226,16 +227,18 @@ where
 
         // New inbound request. Store the stream and tag the output.
         let delay_key = self.inbound_substreams_delay.insert(
-            self.current_substream_id,
+            self.current_inbound_substream_id,
             Duration::from_secs(RESPONSE_TIMEOUT),
         );
         let awaiting_stream = InboundSubstreamState::ResponseIdle(substream);
-        self.inbound_substreams
-            .insert(self.current_substream_id, (awaiting_stream, delay_key));
+        self.inbound_substreams.insert(
+            self.current_inbound_substream_id,
+            (awaiting_stream, delay_key),
+        );
 
         self.events_out
-            .push(RPCEvent::Request(self.current_substream_id, req));
-        self.current_substream_id += 1;
+            .push(RPCEvent::Request(self.current_inbound_substream_id, req));
+        self.current_inbound_substream_id += 1;
     }
 
     fn inject_fully_negotiated_outbound(
@@ -306,11 +309,10 @@ where
                                 if res_is_multiple =>
                             {
                                 // the stream is in use, add the request to a pending queue
-                                (*self
-                                    .queued_outbound_items
+                                self.queued_outbound_items
                                     .entry(rpc_id)
-                                    .or_insert_with(Vec::new))
-                                .push(response);
+                                    .or_insert_with(Vec::new)
+                                    .push(response);
 
                                 // return the state
                                 *substream_state = InboundSubstreamState::ResponsePendingSend {
@@ -431,13 +433,57 @@ where
             self.events_out.shrink_to_fit();
         }
 
-        // purge expired inbound substreams
+        // purge expired inbound substreams and send an error
         while let Async::Ready(Some(stream_id)) = self
             .inbound_substreams_delay
             .poll()
             .map_err(|_| ProtocolsHandlerUpgrErr::Timer)?
         {
-            self.inbound_substreams.remove(stream_id.get_ref());
+            let rpc_id = stream_id.get_ref();
+
+            // handle a stream timeout for various states
+            if let Some((substream_state, _)) = self.inbound_substreams.get_mut(rpc_id) {
+                // When terminating a stream, report the stream termination to the requesting user via
+                // an RPC error
+                let error = RPCErrorResponse::ServerError(ErrorMessage {
+                    error_message: "Request timed out".as_bytes().to_vec(),
+                });
+                // The stream termination type is irrelevant, this will terminate the
+                // stream
+                let stream_termination =
+                    RPCErrorResponse::StreamTermination(ResponseTermination::BlocksByRange);
+
+                match std::mem::replace(substream_state, InboundSubstreamState::Poisoned) {
+                    InboundSubstreamState::ResponsePendingSend { substream, closing } => {
+                        if !closing {
+                            // if the stream is not closing, add an error to the stream queue and exit
+                            let queue = self
+                                .queued_outbound_items
+                                .entry(*rpc_id)
+                                .or_insert_with(Vec::new);
+                            queue.push(error);
+                            queue.push(stream_termination);
+                        }
+                        // if the stream is closing after the send, allow it to finish
+
+                        *substream_state =
+                            InboundSubstreamState::ResponsePendingSend { substream, closing }
+                    }
+                    InboundSubstreamState::ResponseIdle(substream) => {
+                        *substream_state = InboundSubstreamState::ResponsePendingSend {
+                            substream: substream.send(error),
+                            closing: true,
+                        };
+                    }
+                    InboundSubstreamState::Closing(substream) => {
+                        // let the stream close
+                        *substream_state = InboundSubstreamState::Closing(substream);
+                    }
+                    InboundSubstreamState::Poisoned => {
+                        unreachable!("Coding error: Timeout poisoned substream")
+                    }
+                };
+            }
         }
 
         // purge expired outbound substreams
@@ -555,7 +601,7 @@ where
                             request,
                         } => match substream.poll() {
                             Ok(Async::Ready(Some(response))) => {
-                                if request.multiple_responses() {
+                                if request.multiple_responses() && !response.is_error() {
                                     entry.get_mut().0 =
                                         OutboundSubstreamState::RequestPendingResponse {
                                             substream,
@@ -565,10 +611,13 @@ where
                                     self.outbound_substreams_delay
                                         .reset(delay_key, Duration::from_secs(RESPONSE_TIMEOUT));
                                 } else {
+                                    // either this is a single response request or we received an
+                                    // error
                                     trace!(self.log, "Closing single stream request");
                                     // only expect a single response, close the stream
                                     entry.get_mut().0 = OutboundSubstreamState::Closing(substream);
                                 }
+
                                 return Ok(Async::Ready(ProtocolsHandlerEvent::Custom(
                                     RPCEvent::Response(request_id, response),
                                 )));
diff --git a/beacon_node/network/src/sync/range_sync/chain.rs b/beacon_node/network/src/sync/range_sync/chain.rs
index 52b47f1086..fac2d82230 100644
--- a/beacon_node/network/src/sync/range_sync/chain.rs
+++ b/beacon_node/network/src/sync/range_sync/chain.rs
@@ -564,6 +564,9 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
     ) -> ProcessingResult {
         batch.retries += 1;
 
+        // TODO: Handle partially downloaded batches. Update this when building a new batch
+        // processor thread.
+
         if batch.retries > MAX_BATCH_RETRIES {
             // chain is unrecoverable, remove it
             ProcessingResult::RemoveChain